Competitiveness of hybrid and inbred rice with junglerice (Echinochloa colona) resistant to auxinic herbicides

Rice (Oryza sativa L.) is a crucial staple food crop, with significant production in Latin America, the Caribbean, and Asia. Weed infestations, such as with auxinic herbicide-resistant junglerice (Echinochloa colona), pose major challenges to rice production, underscoring the need for additional weed management tools, such as planting weed-competitive rice. This study evaluated the competitive ability of auxinic herbicide-resistant junglerice, with hybrid and inbred rice. Various junglerice accessions were collected and evaluated for their response to quinclorac at rates of 560 and 1,120 g a.i. ha⁻¹. Subsequently, cross-resistance to florpyrauxifen-benzyl (FPB) was assessed using one accession with high resistance to quinclorac in dose–response assays. The intraspecific competitiveness of susceptible and resistant junglerice was evaluated in a replacement series experiment. Likewise, interspecific competitiveness of susceptible and resistant junglerice against inbred and hybrid rice was evaluated using the same approach. Large-scale testing with quinclorac indicated poor control of all junglerice accessions, achieving less than 70% control at the high rate. The one resistant accession (AR) tested showed 30-fold resistance to quinclorac and 2-fold resistance to FPB compared to the susceptible accession (UM). Under intraspecific competition, the resistant and susceptible junglerice were equally competitive, with a potential fitness penalty in the resistant population. The interspecific study suggested that, regardless of the resistance trait, junglerice was more competitive than the rice cultivars evaluated. AR biomass and leaf area exceeded those of inbred rice by ~115% and ~82% but exceeded hybrid rice by only ~70% and ~35%, respectively. This showed 21% and 26% lower relative advantage of inbred compared to hybrid rice. Breeding and planting competitive rice varieties is an ecologically viable strategy to combat weed resistance, especially in disadvantaged regions where other weed control options are limited.

1 Introduction

Rice (Oryza sativa L.) contributes 20% of the total daily caloric intake, with a per capita consumption of approximately 53 kg and a self-sufficiency ratio of 99.4% worldwide (FAO, 2025). Thus, rice produced in developing countries directly contributes to the food security of each country. Latin America and the Caribbean produced 26 million tons of paddy rice in 4.4 million ha in 2024, with an average yield of 5.9 tons ha⁻¹, where the top six countries—Brazil, Peru, Colombia, Uruguay, Ecuador, and Argentina—contributed 10.2, 3.3, 3.0, 1.4, 1.3, and 1.1 million tons, respectively (FAO, 2025). The rest of global rice production is in Asia, totaling 799 million tons. Vast efforts have been dedicated to improving rice yields through breeding programs, aiming to ensure food security in this region (Dass et al., 2017).

Weeds can cause yield and grain quality losses of rice from 70% to 80% in a direct-seeded production system and 50% to 60% in a transplanted system, depending on the weed species composition, level of weed infestation, and other factors that modify the competition interaction between crop and weed (Dass et al., 2017). Weedy rice (Oryza sativa), Echinochloa spp., and Cyperus spp. are the most common and problematic weed complexes in rice production (Kraehmer et al., 2016). The same species are still the most problematic in rice production in North America today (Butts et al., 2022). Among the Echinochloa spp. complex, junglerice is the most important in the tropical and subtropical regions of Latin America and the Caribbean (Fischer et al., 1997). junglerice control heavily depends on herbicides due to their practicality and the lack of supplemental weed management tools.

The sustained selection pressure from herbicide use has resulted in the evolution of junglerice resistance to multiple rice herbicides as has commonly occurred among several weed species in various crops (Roma-Burgos et al., 2019). Out of 27 unique cases of herbicide-resistant junglerice reported globally, 21 are in rice in 13 countries involving 5 herbicide modes of action, including auxinic herbicides (Heap, 2025). Quinclorac and florpyrauxifen-benzyl (FPB) are auxinic herbicides (HRAC #4), which selectively control broadleaf and grass weeds in rice.

junglerice has high morphological plasticity. Its morphological architecture and growth habit changes depending on the plant density (Picapietra and Acciaresi, 2024). Growth characteristics can also be modified by herbicide-resistance trait. It has been reported that glyphosate-resistant junglerice grow more vigorously than their susceptible counterparts (Shrestha et al., 2018), although increased vigor could have been partly due to ecotypic differences between populations. In controlled evolution studies, resistant junglerice showed similar seed production compared to the susceptible counterpart after five iterative cycles of exposure to sublethal doses of quinclorac or FPB (Velasquez and Roma-Burgos, 2024). Other researchers reported no differences in intraspecific competitiveness of barnyard grass (Echinochloa crus-galli (L) P.Beauv) resistant to propanil or clomazone and of late watergrass (Echinochloa phyllopogon L.) with multiple resistance to penoxsulam and quinclorac relative to their respective susceptible counterparts (Bagavathiannan et al., 2011; Papapanagiotou et al., 2023). Herbicide-resistant weeds may exhibit different levels of competitiveness depending on the herbicide resistance trait(s) they carry, the cropping system, and the resistance mechanisms involved. Thus far, the competitive ability of the cross-resistance of junglerice to quinclorac and FPB has not been studied.

Previous research has demonstrated that rice biomass accumulation at 36 and 40 days after emergence is a strong predictor for rice yield (Fischer et al., 1997; de Vida et al., 2006). In fact, early biomass accumulation and light interception are the important variables correlated with rice yield under weed pressure (de Vida et al., 2006; Saito, 2010). The competition of junglerice with rice is more related to shoot biomass than root biomass (Chauhan and Johnson, 2010). The competitive ability of Echinochloa spp. with rice is well documented (Fischer et al., 1997; Galon et al., 2007; Agostinetto et al., 2008), but the studies conducted only involved inbred rice. On the other hand, hybrid rice has been documented as more competitive with weeds than inbred rice, for example, with saramollagrass (Ischaemum rugosum Salisb.) (Awan et al., 2018) or weedy rice (Shivrain et al., 2009). However, hybrid vigor is not universal across environments, and its expression may vary depending on temperature, soil fertility, water availability, and weed pressure. Experimental evidence is limited with respect to the stability of hybrid vigor across environments in the context of weed competition. Rice breeding programs select promising lines based on yield under weed-free conditions; however, yield performance in clean culture is not guaranteed to correlate with performance in weedy conditions. Breeding for weed-competitive traits is yet to be integrated into rice breeding programs, and characterization of contemporary varieties for weed competitiveness needs to be done more broadly.

It is crucial to develop and implement ecological strategies for weed management, such as breeding for weed-competitive traits in rice. This will not only increase rice production but will also help curtail the evolution of herbicide-resistant weeds. Weed resistance to herbicides could confer fitness advantage to the weed (Boddy et al., 2012; Shrestha et al., 2018). Considering the possibility that evolving resistance to herbicides might also confer increased weediness and the potential difference in competitive abilities between inbred and hybrid rice, we aimed to determine whether 1) auxinic-herbicide-resistant junglerice is more competitive than susceptible junglerice and 2) hybrid rice is more competitive with junglerice than inbred rice.

2 Materials and methods

2.1 Plant material and screening for quinclorac resistance

Eighteen junglerice populations (Supplementary Figure 1) were collected from five rice-producing regions in Colombia (Magdalena, Meta, Norte de Santander, Sucre, and Tolima). Four seedlings from each population were established in pots filled with 500 g of potting soil (Klasmann^®):soil mixture and placed in a greenhouse set at 32°C/23°C, day/night temperature with a relative humidity of 28.2%–65.8% at the National University of Colombia, Bogotá campus. Seedlings at V₃–V₄ were sprayed with 1 and 2× the commercial rate of quinclorac (560 and 1,120 g a.i. ha⁻¹, respectively; Quinclofed^® 250 SC, FEDEARROZ) using a spray chamber with a spray boom fitted with one flat-fan nozzle (Tee-Jet XR-8001), calibrated to deliver 125.8 L ha⁻¹ spray volume at a speed of 0.7 m s⁻¹ and 2.81 kg cm⁻² air pressure. Herbicide treatments contained 1.5% v/v emulsified mineral oil (Cosmo Oil, COSMOAGRO). The experimental units (pots) were arranged in a completely randomized design with four replications, and the test was conducted twice. Herbicide efficacy (% control) was evaluated visually 21 days after treatment (DAT) using a scale of 0% to 100%, where 0% indicates no visible effect compared to the non-treated check and 100% indicates dead plants. Efficacy data were analyzed using descriptive statistics, and populations were classified according to the level of damage caused by the treatment. The effect of treatments was similar across repetitions (p-value for repetition = 0.765); therefore, the data were pooled across repetitions in the analysis. Resistant (R: 10% to 54% control) and highly resistant (HR: 0% to 9% control) junglerice accessions were cultured for seed production. Susceptible (S: 75% to 100% control) junglerice accession was cultured separately from the resistant plants. Seeds were collected and stored at room temperature for 3 months and used in follow-up experiments.

2.2 Dose–response assay for quinclorac

Following the same methods for the resistance screening assay, four seedlings were established per pot from susceptible (S-UM) and highly resistant (HR-AR) junglerice populations. At the V₃–V₄ growth stage, seedlings were sprayed as described in Section 2.1. The S population was treated with quinclorac at 0, 0.25, 0.5, 1, 2, 4, and 8 times the commercial rate (560 g a.i. ha⁻¹), and the HR populations were treated at 0, 0.5, 1, 2, 4, 8, 16, and 32 times the commercial rate. The experimental design was a split-plot with five replications, where the junglerice population was the whole plot and the quinclorac rate was the subplot. Control level (%) was evaluated as previously described. Shoot biomass was collected at 21 DAT, oven-dried at 80°C for 72 h, and weighed using a precision balance (Denver Instrument Company Model 100A XE Series). The experiment was repeated.

2.3 Dose–response assay for florpyrauxifen-benzyl

The FPB dose–response assay was conducted in a greenhouse set at 40°C/26°C, day/night temperature with relative humidity between 28.2% and 65.8% at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia. Four seedlings from each junglerice population, UM (quinclorac-S) and AR (quinclorac-HR), were established in pots filled with 500 g of heat-sterilized soil (4% OM, pH 7.8, Vertisols) collected from the CIAT research field. Seedlings at V₂–V₃ were sprayed outdoors with FPB at 0, 0.5, 1, 1.5, 2, 3, and 4 times the commercial rate (30 g a.i. ha⁻¹; Loyant Neo EC^®, CORTEVA) using a pressurized backpack sprayer (RoyalCondor, CO-018), equipped with four air-induced flat fan nozzles (Tee-jet AI-110015) 50 cm apart, calibrated to deliver 193.3 L ha⁻¹ spray volume at a speed of 1 m s⁻¹ and 2.81 kg cm⁻² air pressure. Herbicide treatments contained 3% v/v non-ionic surfactant (INEX-A, COSMOAGRO). The experimental units were arranged in a split-plot design with four replications, where population was the whole plot and the FPB rate was the subplot. Control level (%) was evaluated as described in Section 2.1, and shoot biomass was harvested at 21 DAT, oven-dried at 80°C for 72 h, and weighed (A&D Weighing, EJ-3000). The experiment was conducted twice.

2.4 Dose–response analysis

A mixed linear model was fitted to the data, considering replication and repetition as random and whole plot and subplot as fixed factors (Supplementary Table 1). Normality of data distribution was checked using plots of residual errors and residual normal quantile (QQ-plots) (Supplementary Material 2 Figures 1, 2). Factor effects were considered significant at a p-value<5%. Data from dose–response experiments were analyzed using a four-parameter log-logistic regression model (Equation 1) using the DRC package (Ritz et al., 2015) in R statistical software, version 3.6.0:

$\begin{array}{ll}y=f(x)=c+\left[\frac{d-c}{1+\text{exp}(b(\log (x)-\log (e)))}\right] & (1)\end{array}$

where c and d are the lower and upper asymptotes of the response (y), respectively, b is the slope of the curve, and e is the rate of the herbicide that results in 50% visible effect, either manifested as 50% efficacy (ED50) or 50% reduction in biomass (GR50). The absolute ED50 and GR50 (ED50, abs and GR50, abs) were calculated by solving the inverse model for y = 50 (Equation 2).

$\begin{array}{ll}E{D}_{50, abs}=e{\left[\frac{d-c}{y-c}\right]}^{1/b}& (2)\end{array}$

The resistance index (RI) was calculated by dividing the ED_{50, abs} value of the resistant junglerice population (AR) by the ED_{50, abs} value of the susceptible population (UM). The data for two repetitions were pooled since the interaction between repetition and herbicide treatment was not significant (Supplementary Table 1). The confidence interval using the delta method and the Akaike information criterion (AIC) are shown in Supplementary Table 2.

2.5 Replacement series experiment

Competition experiments were conducted in a greenhouse (40°C/26°C, day/night temperature) at CIAT, Palmira campus, between September 2023 and July 2024. Before conducting the study, carrying capacity (K) assays were performed to determine the maximum number of rice and junglerice plants that the pots (experimental unit) can support. The law of constant final yield states that once a certain plant density is reached, the yield per unit area becomes independent of plant density (Radosevich and Holt, 2007). Inbred rice ‘FL1566’ and junglerice (R) monocultures were sown in pots (16-cm diameter) filled with 1.5 kg of soil (4% OM, pH 7.8, Vertisols). The plant densities were 1, 2, 4, 8, 16, 32, and 64 plants pot⁻¹ (equivalent to 50, 100, 200, 400, 800, 1,600, and 3,200 plants m⁻²). Shoot biomass was collected 45 days after emergence, oven-dried at 80°C for 72 h, and weighed (A&D Weighing, EJ-3000). K was reached at 12 plants pot⁻¹ (600 plants m⁻²) for junglerice and 9 plants pot⁻¹ (450 plants m⁻²) for rice. The highest supported density (12 plants pot⁻¹) was selected and used for all the replacement series experiments.

The two junglerice populations previously characterized for resistance to quinclorac and FPB (UM and AR) and two rice lines—hybrid HL23057 and inbred SLF16007—were used to establish five replacement series treatments (UM vs. AR, AR vs. HL23057, AR vs. SLF16007, UM vs. HL23057, and UM vs. SLF16007). Latin America and Caribbean rice breeding programs are focused on improving hybrid lines for vigor and yield. Therefore, the HL23057 hybrid and SLF16007 inbred rice lines were selected to evaluate their competitiveness. Using the established K total plant density, seeds from the respective species were sown in an equidistant 12-plant grid pattern in 16-cm diameter pots filled with 1.5 kg of soil (4% OM, pH 7.8, Vertisols). After emergence, seedlings were thinned to 1 plant per grid point. Five proportions of each competing species were established: 100:0 (monoculture species A), 75:25, 50:50, 25:75, and 0:100 (monoculture species B). The total plant density was constant (12 plants pot⁻¹) across all treatments. The soil was maintained at field capacity for the whole duration of the experiment. Fertilizer was applied at 200 kg ha⁻¹ of N, 7.3 kg ha⁻¹ of Zn, and 21 kg ha⁻¹ of Fe. Fertilizer (N = 25%, Zn = 100%, and Fe = 100%) was applied 5 days after sowing and 25 days after emergence (N = 50%). Each replacement series pair (i.e., UM vs. AR and so forth) was considered an independent experiment. Each series was conducted as a split-plot, where the whole plot was the competing species (two levels) and the subplot was the replacement proportion (four levels), in a randomized complete block design with five replications. The experiment was conducted twice (repetition).

At 35 days after emergence, leaf area was measured using a leaf area meter (LI−COR LI 3100C). Shoots were harvested, oven-dried at 45°C for 96 h, and weighed using a precision scale (A&D Weighing, EJ-3000). A mixed linear model was fitted considering replication (blocks) and repetition as random and whole plot and subplot as fixed factors (Supplementary Table 3). Normality of data distribution was checked by looking at plots of residual errors and residual normal quantile (or QQ-plots) (Supplementary Material 2 Figures 3-Supplementary Material 2 Figures 5). The effect of factors where the p-value<5% is considered significant.

The data from the UM vs. AR series are presented separately by repetition because of a significant interaction between repetition and species (Supplementary Table 3). The data for the remaining series (AR vs. HL23057, AR vs. SLF16007, UM vs. HL23057, and UM vs. SLF16007) were pooled due to the absence of significant interaction repetition factors and interactions (Supplementary Table 3). The only exception was the leaf area of UM vs. inbred rice (SLF16007), where repetition alone and its interaction with proportion were significant. Dunnett’s test was performed to compare means (at the 95% level of confidence) with the monoculture by each series. All analyses were performed using JMP statistical software, version 18.0.0.

For each response variable, relative yield (RY) and total relative yield (TRY) were calculated and plotted by species using the following formula:

$$\text{RY }(A)=\text{P} (\frac{A_{\text{mix}}}{A_{\text{mono}}})$$

$$\text{RY }(B)=(1-\text{P}) (\frac{B_{\text{mix}}}{B_{\text{mono}}})$$

$$\text{TRY}=\text{RY}(A)+\text{RY}(B)$$

where RY(A) and RY(B) are relative yields of A and B species, respectively. P is the proportion of species A or B in mixed stands. A_mix and B_mix are the yields of species A or B in mixture, respectively. A_mono and B_mono are the yields of species A or B in monoculture, respectively. Diagrammatic visualization of replacement series data was done by plotting TRY and RY for each replacement series experiment with “neutral-interaction” lines (reference lines) of each species in the absence of interference. A convex TRY line, compared to the expected value (horizontal dashed line), indicates a negative effect of one species on the other, while a concave TRY line indicates a beneficial effect on at least one species (Radosevich and Holt, 2007). A Student’s t-test was performed on the data on each treatment by species to compare to the corresponding expected RT and TRY values (Supplementary Tables 4, 6).

Relative competitiveness index (CR) and competitiveness coefficient (C) were calculated for leaf area and shoot biomass at the 50:50 proportion. The 50:50 proportion was selected to observe the response of each species when competing at equal densities (Cousens and Neill, 1993) (Supplementary Material 2). CR compares the growth of species A relative to species B, and C indicates which species is more competitive than the other (Cousens, 1991). Species A is more competitive than B when CR >1 and C >0. Conversely, species B is more competitive than A when CR<1 and C<0 (Hoffman and Buhler, 2002). For the intraspecific experiment, AR was “species A,” and UM was “species B.” For the interspecific experiment, “species A” was junglerice (either AR or UM) and “species B” was rice (either HL23057 or SLF16007). A Student’s t-test was used to determine whether CR or C is different from the expected value of 1.0 and 0, respectively (α = 0.05).

3 Results

3.1 Screening for quinclorac resistance

The commercial rate of quinclorac (560 g a.i. ha⁻¹) controlled the susceptible accession (UM) 75%. Among the putative resistant (R) accessions, 1 accession (PG) was classified slightly resistant (SR), 12 were resistant (R), and 4 were highly resistant (HR) (Figure 1). At double the commercial rate of quinclorac (1,200 g a.i. ha⁻¹), the control of UM accession was higher than that with the 1× rate, as expected, but not by much (89%). This indicates that at least some “non-selected” Echinochloa populations in Colombia could not be controlled with the 1× rate of quinclorac to begin with, unlike the susceptible populations in the US, for example (Rouse et al., 2018). The number of resistant accessions remained at 12, but the HR accessions dropped to only 1, as the remaining accessions were controlled better with the 2× than the 1× rate. The AR accession was classified HR (control<10%) even with the 2× rate of quinclorac. The majority of junglerice accessions tested were classified as resistant to the commercial rate of quinclorac. Even the 2× rate of quinclorac did not control any of the putative R populations 70%, except for the susceptible standard UM. We selected two accessions (AR and UM), which originated from the same region, for further studies.

Figure 1

Figure 1. Control of 18 Colombian Echinochloa colona populations, 21 days after treatment with 1× and 2× doses of quinclorac (560 and 1,120 g a.i. ha⁻¹, respectively). Resistance classification: blue = susceptible (S), green = slightly resistant (SR), yellow = resistant (R), and red = highly resistant (HR). Error bars are the standard error of the mean (n = 8).

3.2 Resistance level to quinclorac and FPB

Dose–response assays were performed using AR junglerice accession as the resistant and UM as the susceptible standard. The quinclorac ED_{50, abs} for UM was 414 g a.i. ha⁻¹, whereas that for AR was 12,505 g a.i. ha⁻¹ (Figure 2, Table 1). Thus, the RI of AR relative to UM, based on the level of control, was 30-fold. The GR_{50, abs} for UM, based on dry shoot biomass, was 544 g a.i. ha⁻¹ of quinclorac. This value was very close to the ED_{50, abs} value. On the other hand, the GR_{50, abs} for AR could not be estimated because it exceeded the maximum rate (32×) of quinclorac tested (Table 1).

Figure 2

Figure 2. Control and biomass (relative to the non-treated check) of auxin herbicide-susceptible (UM) and auxin herbicide-resistant (AR) junglerice (Echinochloa colona) accessions in response to increasing doses of quinclorac (A, C) and florpyrauxifen-benzyl (B, D), 21 days after treatment. Each data point is an average of four replications and two repetitions (n = 8).

Table 1

Table 1. Parameters of the logistic model for the control level and shoot biomass production of auxin herbicide-susceptible (UM) and auxin herbicide-resistant (AR) junglerice in response to increasing doses of quinclorac and florpyrauxifen-benzyl, 21 days after treatment.

The FPB ED_{50, abs} for AR was 36 g a.i. ha⁻¹, and for UM, it was 19 g a.i. ha⁻¹ (Figure 2, Table 1). The RI of AR relative to UM with respect to FPB was 2.2-fold. The GR_{50, abs} values were 36 and 18 g a.i. ha⁻¹ for AR and UM, respectively. Thus, the RI was approximately 2-fold, whether based on the level of control or shoot biomass reduction. These results confirmed the high resistance level of AR to quinclorac and the low-level resistance to FPB, the commercial rate being 30 g a.i. ha⁻¹ (Supplementary Figure 2).

3.3 Replacement series: intraspecific competitiveness

To evaluate whether resistance of AR to auxinic inhibitors has influenced its competitiveness, AR was grown with susceptible standard UM in a replacement series experiment. The data for each repetition are presented separately because of a significant interaction between repetition and species (Supplementary Table 3). The interaction of whole plot (species in competition) and subplot (replacement proportion) was significant for both biomass and leaf area. The data for these experiments are presented as values relative to the monoculture or RY (diagonal lines) for each competing species or genotype (Figure 3). The dashed diagonal lines represent the reduction in RY of each competing species as a fraction of one species (rice) is replaced by another (junglerice), if intra- and interspecific interactions are equal. Hereafter, these will be referred to as the “neutral-interaction” reference line. The horizontal dotted line is the total relative yield (TRY) of the competing species, which is equal to 1 if the interaction is neutral, where the competing species or genotypes have no negative or positive effect on one another.

Figure 3

Figure 3. Relative yield for leaf area (A, B) and biomass (C, D) of auxin herbicide-resistant (AR) and auxin herbicide-susceptible (UM) junglerice (Echinochloa colona) as a function of plant density proportions between accessions. Data points are means (n = 4) for the first run (A, C) and the second run (B, D). Dashed lines are the neutral-interaction yield lines (reference line) as plants of one accession are replaced with increasing proportions of another, when the interaction between each genotype is neutral.

For the first-run experiment, the TRY lines for leaf area and biomass per plant were convex (Figures 3A, C). The TRY values for leaf area and biomass were significantly below the reference line at 75:25 and 25:75 proportions, respectively (Supplementary Table 4), showing competitive interaction between the resistant and susceptible junglerice plants. The relative yield of AR, in terms of leaf area and biomass, fell below the reference line when grown with increasing proportions of UM (Figures 3A, C; Supplementary Table 4). The leaf area of AR declined as any proportion of AR plants was replaced with UM, although the reduction was not significant compared to the AR monoculture (Table 2). On the contrary, the UM leaf area at the 75AR:25UM proportion (3 UM plants pot⁻¹) was 40% points higher than that of the UM monoculture (12 UM plants pot⁻¹) (Table 2). In the second run, the TRY lines for leaf area and biomass per plant were above the reference for proportions 75:25 and 25:75 (AR: UM), being only different from 1 in terms of leaf area at the 75:25 (AR: UM) proportion (Figures 3B, D; Supplementary Table 4). This is due to numerically improved performance of both populations, where both populations developed more leaf area at this proportion compared to their respective monocultures (Table 2). The AR leaf area at the 50:50 proportion was significantly reduced compared to the AR monoculture (Table 2). As in the first run, replacement of some UM plants with AR plants did not reduce the UM leaf area. Although not as stark as in the first run, the leaf area of UM was numerically higher than the UM monoculture when growing with three times the number of AR plants.

Table 2

Table 2. Leaf area and biomass of auxin herbicide-resistant (AR) and auxin herbicide-susceptible (UM) junglerice (Echinochloa colona) in the replacement series experiments, 35 days after emergence.

We attributed the differences between the runs for leaf area and biomass to early maturation of the susceptible population (UM) in the second run. The main environmental difference between the first and second run was the lower radiation during the latter, which apparently triggered early maturation of UM (Supplementary Material 2 Table 1). We noticed that the early-maturing UM plants were shorter, which also reduced leaf development. This was advantageous to AR, especially at the 25AR:75UM proportion. Despite this, the leaf area of UM remained above the reference line, similar to the first run.

The biomass per plant of AR was significantly reduced by 28% on average by the coexistence of UM plants across density proportions in the first run (Table 2). In contrast, UM biomass tended to increase as some plants were replaced with AR plants, producing 35% higher biomass when only one-fourth of the UM plants remained at the 75AR:25UM proportion. In the second run, AR biomass was not reduced by the UM coexistence, but the UM biomass increased 29% when only one-fourth of the UM plants remained at the 75AR:25UM proportion, the same as what was observed in the first run. These results suggest that the quinclorac-resistant junglerice (AR) is less competitive than its susceptible counterpart (UM).

The indices for plant–plant interaction were not different across repetition, except for C for biomass (Supplementary Table 5). The C index for biomass (−0.18) was different from 0 (p-value = 0.004) in the first repetition, but this difference was marginally significant in the second repetition (−0.09, p-value = 0.100). The C value for leaf area was<0 (−0.16, p-value = 0.052). The CR values for leaf area (0.78) and biomass (0.83) were not different from 1 (p-value = 0.139 and 0.099, respectively). Collectively, these indices suggest that there is no difference in competitiveness between the auxinic-herbicide-resistant and auxinic-herbicide-susceptible junglerice. Therefore, resistance to auxins did not increase the competitiveness of AR junglerice. Instead, there was an indication of a physiological penalty based on the negative effect of replacing some AR with UM plants with respect to biomass and leaf area per plant.

3.4 Interspecific competitiveness of hybrid and inbred rice to quinclorac-resistant and quinclorac-susceptible junglerice

Previous studies suggested that the quinclorac-susceptible UM was more competitive than its resistant counterpart (AR). To evaluate the competitiveness of the recent hybrid rice line and the inbred variety for Latin America to quinclorac-resistant junglerice, four replacement series experiments were established to evaluate the interaction of AR or UM with hybrid and inbred rice. We hypothesized that hybrid rice competes better than inbred rice with quinclorac-resistant or quinclorac-susceptible junglerice. In all the experiments, the interaction of whole plot (species in competition) and subplot (replacement proportion) was significant for both leaf area and biomass (Supplementary Table 3).

3.4.1 Quinclorac-susceptible junglerice (UM) vs. hybrid and inbred rice

The RY lines for leaf area and biomass were similar, being above the “neutral-interaction” reference lines for UM and below the reference line for hybrid rice (Figures 4A, C; Supplementary Table 6). Similarly, the RY lines for leaf area and biomass were above the “neutral-interaction” reference lines for UM and below the reference line for inbred rice (Figures 4B, D; Supplementary Table 6). This suggests that both hybrid and inbred rice were negatively affected by UM junglerice. At the 75:25 proportion of junglerice:hybrid rice (9 junglerice vs. 3 rice), the TRY for leaf area was above the reference line, whereas the TRY for biomass was the same as the reference line (Supplementary Table 6). This improved combined performance of junglerice and hybrid rice was due to less impact on hybrid rice at low rice densities (three plants) and the increase in leaf area per plant of UM but not necessarily increasing its biomass. On the other hand, the TRY for leaf area did not deviate from the “neutral-interaction” reference line in junglerice:inbred rice, whereas the TRY for biomass at the 25:75 proportion of junglerice:inbred rice (3 junglerice vs. 9 rice) was above the reference line. The higher combined biomass production of the two species was due to increased biomass of UM when coexisting with 9 inbred rice plants and less impact of low UM on higher inbred rice density. This suggests that UM tolerated higher light interception rhizosphere exploration by inbred rice.

Figure 4

Figure 4. Relative yield of auxinic herbicide-susceptible junglerice (Echinochloa colona, UM) and hybrid rice (Oryza sativa ‘HL23057’); (A, C) and inbred rice (Oryza sativa ‘SLF16007’); (B, D) as a function of plant density proportions between species, 35 days after emergence. Each data point is an average of four replications and two runs (n = 8); dashed lines are the neutral-interaction yield lines (reference line) as plants of one species are replaced with increasing proportions of another, when the interaction between species is neutral. Deviations from these lines reflect competitive interactions between species.

The leaf area per plant of UM increased by 50% and 57%, respectively, at the 75:25 and 25:75 UM:hybrid rice proportions compared to its monoculture (Table 3). The hybrid rice leaf area was significantly reduced by 25% and 14%, respectively, at the 50:50 and 75:25 UM:hybrid rice proportions. The leaf area plant⁻¹ for the UM:inbred rice was the only variable significantly affected by the interaction of repetition and species (Supplementary Table 3). However, the pattern of leaf area development was similar between trials (Table 4). Consistent with the UM:hybrid rice series, UM leaf area tended to increase as some plants were replaced with inbred rice compared to the monoculture, up to 61% higher across trials at one-third (3 plants pot⁻¹) of UM vs. inbred rice (9 plants pot⁻¹) (Table 4). The leaf area of inbred rice declined as it coexisted with more UM plants in both trials.

Table 3

Table 3. Response of hybrid rice (Oryza sativa, HL23057) and inbred rice (Oryza sativa, SLF16007) to interference of auxin herbicide-susceptible junglerice (Echinochloa colona, UM), 35 days after emergence.

Table 4

Table 4. Response of inbred rice (Oryza sativa, SLF16007) to interference of auxin herbicide-susceptible junglerice (Echinochloa colona, UM), 35 days after emergence.

The biomass per plant of UM tended to increase in the presence of more hybrid rice plants, producing 72% more biomass when 3 UM plants coexisted with 9 hybrid rice plants. Conversely, hybrid rice biomass was significantly reduced by 22%, 33%, and 17% compared to its monoculture when 9, 6, and 3 rice plants competed with 3, 6, and 9 UM junglerice, respectively. Similarly, the biomass of UM tended to increase, while the biomass of inbred rice tended to decrease relative to their respective monocultures when weed and crop coexisted (Table 3). UM biomass increased up to 75% more at 3 UM vs. 9 inbred rice (25:75 proportion). The biomass reduction of inbred rice reached 22% at 50:50 and 75:25 proportions of UM vs. inbred rice and 11% at the 75:25 proportion compared to its monoculture.

The fact that both variables showed the same response indicates that the quinclorac-susceptible junglerice was more competitive than hybrid rice. Overall, both hybrid and inbred rice were negatively affected by the interspecific competitiveness of UM, and neither rice type suppressed the growth of UM. The intraspecific competition among herbicide-susceptible junglerice was stronger than interspecific competition with rice. Hybrid and inbred rice exhibited similar competitive ability with susceptible junglerice. UM showed better vigor when in competition with rice than in monoculture.

3.4.2 Quinclorac-resistant junglerice (AR) vs. hybrid and inbred rice

The experiments presented previously showed that regardless of rice type (hybrid or inbred), UM reduced rice growth. Another replacement series experiment was established to evaluate whether the quinclorac-resistant junglerice (AR) is more competitive with hybrid and inbred rice than the susceptible junglerice.

The leaf area and biomass RY for hybrid rice were below the neutral-interaction reference lines, showing a negative effect of AR (Figures 5A, C; Supplementary Table 6). On the other hand, AR junglerice showed values above the reference line only at low densities 25:75 (3 junglerice vs. 9 hybrid rice) for leaf area and at 50:50 and 25:75 proportions for biomass. Consequently, the TRY lines for leaf area and biomass tended to be convex (below the reference line) (Figures 5A, C; Supplementary Table 6). Similar to what was observed in the AR:hybrid rice replacement series study, the RYs for leaf area and biomass of inbred rice were below the reference line (Figures 5B, D). On the other hand, the RYs of AR were markedly above the reference lines when growing with inbred rice but were significantly depressed by hybrid rice. This suggests that inbred rice caused less interference with AR than hybrid rice.

Figure 5

Figure 5. Relative yield of auxin herbicide-resistant junglerice (Echinochloa colona, AR) and hybrid rice (Oryza sativa ‘HL23057’); (A, C) and inbred rice (Oryza sativa ‘SLF16007’); (B, D) as a function of plant density proportions between species, 35 days after emergence. Each data point is an average of four replications and two runs (n = 8); dashed lines are the neutral-interaction yield lines (reference line) as plants of one species are replaced with increasing proportions of another, when the interaction between species is neutral. Deviations from these lines reflect competitive interactions between species.

The TRY for leaf area of AR:hybrid rice was slightly concave but not significantly different from the reference line, whereas the TRY for biomass was markedly concave (Figures 5B, D; Supplementary Table 6). The TRY of biomass of AR:hybrid rice was different from the biomass TRY of AR:hybrid rice. The TRY above the hypothetical line indicates that at least one species benefits from the other; in this case, the quinclorac-resistant junglerice (AR) benefited from competition with inbred rice.

The leaf area of AR tended to increase as plants were replaced with hybrid rice, but it was not different compared to the monoculture (Table 5). The hybrid rice leaf area generally declined as rice was replaced with AR and was significantly reduced by 30% compared to the rice monoculture at the 75:25 proportion (9 junglerice vs. 3 hybrid rice). On the other hand, the leaf area of AR was higher than the monoculture when in competition with inbred rice, reaching 65%, 36%, and 82% at 9 vs. 3, 6 vs. 6, and 3 vs. 9, AR vs. inbred rice, respectively (Table 5). Consequently, the leaf area of inbred rice was lower than its monoculture by 24% and 28% at 6:6 and 9:3 AR:inbred rice, respectively. The biomass of AR increased compared to its monoculture by 27% and 70%, respectively, at 50:50 and 25:75 AR:hybrid rice proportions (Table 5). Conversely, hybrid rice biomass decreased by 22% compared to the monoculture at 25:75 and 75:25 AR:hybrid rice and by 27% when AR and hybrid rice were at equal densities. Similarly, the AR biomass increased when competing with inbred rice by 30%, 54%, and 115% at 9:3, 6:6, and 3:9 AR:inbred rice, respectively, compared to its monoculture (Table 5). Inbred rice biomass was reduced by the coexistence of AR by 17% for 9 vs. 3 and 3 vs. 9 AR vs. inbred rice and by 22% at equal densities. This was in agreement with the RY curves, showing better growth of resistant junglerice (AR) when competing with inbred rice. However, the effect of AR on both rice varieties was similar. This suggests that despite the bigger AR plants competing with inbred rice, the effect on rice growth was not different between inbred and hybrid rice.

Table 5

Table 5. Response of hybrid rice (Oryza sativa, HL23057) and inbred rice (Oryza sativa, SLF16007) to interference of auxin herbicide-resistant junglerice (Echinochloa colona, AR), 35 days after emergence.

Overall, both hybrid and inbred rice were negatively affected by the competitiveness of AR. The growth of AR was greater (up to 115% more biomass than monoculture) with inbred rice than with hybrid rice, where AR only had 70% more biomass. This resulted in a 21% lower relative advantage of AR biomass accumulation with the hybrid. Although the leaf area of AR competing with hybrid rice (3 AR vs. 9 rice) was not significantly different from the monoculture, the advantage was 35%, which, compared to that of inbred rice (82%), equated to a 26% lower relative advantage of inbred rice compared to hybrid rice. Therefore, the hybrid rice tested had a higher ability than inbred rice to compete with AR.

3.5 Competition indices of quinclorac-susceptible and quinclorac-resistant junglerice and hybrid or inbred rice

Relative competitiveness index (CR) and competitiveness coefficient (C) were calculated for leaf area and shoot biomass at the 50:50 proportion. CR compares the growth of junglerice (either AR or UM) relative to rice (either HL23057 or SLF16007), and C indicates which species is more competitive than the other (Cousens, 1991). junglerice (either AR or UM) is more competitive than rice (either HL23057 or SLF16007) when CR >1 and C >0. The opposite will be concluded when CR<1 and C<0. The indices did not differ between repetitions based on a t-test at the 95% confidence level (Supplementary Table 7). Therefore, we pooled the data from both repetitions.

The CR values of both junglerice populations (AR or UM) vs. both rice types were significantly above 1, and the C values of junglerice were consistently above 0, suggesting that, regardless of its resistance trait, junglerice is more competitive than hybrid and inbred rice for the variables evaluated (Supplementary Table 8). The calculated indices support the data presented; thus, we fail to reject the null hypothesis. We concluded that the quinclorac-resistance trait does not increase the competitiveness of junglerice with rice. Although other variables such as SPAD readings, plant height, and tillering were recorded in these experiments (data not shown), they were not influenced by species interactions across treatments. Biomass and leaf area were the most responsive indicators of competitive effects, allowing a clearer understanding of species interactions. Other traits such as root development and early light interception could further influence competition dynamics. These could be included in follow-up studies to fully investigate the mechanisms of interference.

4 Discussion

4.1 Junglerice resistance to quinclorac

The junglerice accessions evaluated in this research were from rice fields in Colombia, including Central, Dry Caribbean, and Humid Caribbean regions with 10, 4, and 4 accessions, respectively (Supplementary Figure 1), mostly with a history of quinclorac use for more than 10 years. The susceptible standard (S) UM accession was from a non-crop site. Rice is also grown in other regions in Colombia, including the Pacific and Orinoquía region, which remains to be surveyed. Overall, accessions from the Dry and Humid Caribbean regions of Colombia exhibited lower levels of control at 1× and 2× rates of quinclorac, showing at least one population not responsive to higher herbicide rates.

Rice farmers in the Central region have adopted more technology compared to farmers in the Caribbean region. This is reflected in superior rice yields, 6.5 to 7.3 t ha⁻¹ in the Central region vs. 4.3 to 6.1 t ha⁻¹ in the Caribbean region (DANE, 2025). Technological advancement includes proper herbicide applications and rotation of herbicide modes of action, among other practices. Therefore, we can surmise that the adoption of proper herbicide technology practices has reduced the overall selection pressure across generations of junglerice in the Central region. Doing otherwise has led to more difficult-to-control populations in the Caribbean region. However, further tests are needed to confirm this by sampling more fields from each region.

Junglerice resistance to quinclorac has been reported in Colombia since 1989 (Heap, 2025). Subsequently, multiple-resistant populations to bispyribac-sodium, cyhalofop-butyl, and quinclorac were reported. Approximately 40% of populations tested were resistant to the commercial dose of quinclorac (270 g a.i. ha⁻¹) in Tolima, the central region of Colombia (Zabala et al., 2019). The populations tested in this current research survived up to 1,120 g a.i. ha⁻¹ of quinclorac in the screening assay, indicating that the resistance level among junglerice populations had increased with time. Healthy survivors were recovered from a 32× dose of the commercial rate of quinclorac in the dose–response assay. This level of resistance has not been reported in Colombia and is indicative of persistent selection pressure from herbicide use.

junglerice resistance to quinclorac is widespread in many rice-producing regions globally, where herbicide is used, including Brazil, Colombia, the USA, and Asia (Tironi et al., 2009; Rouse et al., 2018; Heap, 2025). In Arkansas, USA, for example, about two-thirds (293 out of 450) of Echinochloa spp. (barnyard grass, junglerice, and rough barnyard grass) accessions are resistant to at least one rice herbicide (clomazone, cyhalofop-butyl, imazethapyr, propanil, or quinclorac), of which 104 were resistant to quinclorac (560 g a.i. ha⁻¹) (Rouse et al., 2018).

Diverse resistance mechanisms to quinclorac have been reported in various Echinochloa spp. populations. These include enhanced metabolism mediated by cytochrome P450 enzymes, cyanide degradation mediated by β-CAS (β-cyanoalanine synthase), regulation of ethylene production by modulating genes such as 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and oxidase (ACO), and differential oxidative stress response (Gao et al., 2018, Gao et al., 2021; Qiong et al., 2019; Chayapakdee et al., 2020; Zia Ul Haq et al., 2020). Further research is needed to understand the specific mechanisms of resistance to quinclorac in these populations from Colombia and to understand how these mechanisms affect weed physiology and weediness.

4.2 Cross-resistance to quinclorac and FPB

Cross-resistance between quinclorac and FPB has been reported previously in junglerice populations (Heap, 2025). Overlapping binding sites in auxin receptors or transporters may explain this, but many auxin-resistant barnyard grass are controlled with FPB due to some differences in affinity with auxin-reactive genetic elements (Miller et al., 2018; Prusinska et al., 2022). Likewise, populations not yet exposed to FPB have been reported to be resistant, possibly due to cross-reactivity with metabolic enzymes that have been overexpressed in resistant populations previously exposed to selection pressure of other herbicide modes of action such as imazamox and penoxsulam (Takano et al., 2023).

The same phenomenon of junglerice cross-resistance to quinclorac and FPB, prior to the adoption of FPB, was documented for the first time in Colombia rice fields. Farmers from Magdalena have not reported using FPB since its release in Colombia in 2019 (Anonymous, 2025). Therefore, it is most likely that mechanisms conferring resistance to one herbicide can also confer resistance to a new, but structurally and physiologically similar herbicide, which would be in the same mode-of-action category. Other researchers have reported that the mechanisms of resistance may involve concomitant action of P450 enzymes and overexpression of the trehalose pathway in highly resistant junglerice (up to 32×) (Rouse et al., 2019; Rangani et al., 2022). For the highly quinclorac-resistant strain from Colombia (32×), increased quinclorac degradation by metabolic enzymes may be involved, as indicated by its cross-resistance with FPB.

This research identified a potential threat to Colombian rice production in the Magdalena region, with respect to auxinic-herbicide-cross-resistant weed populations. Agronomically, high resistance (30-fold) to quinclorac implies that quinclorac should not be utilized in the region as a post-emergence option for junglerice control. On the other hand, the low resistance to FPB (2-fold) alerts farmers, agronomists, agrichemical manufacturers and dealers, and government institutions about the threat of the weed-resistance-preselection phenomenon. This information would lend support to weed-resistance mitigation recommendations, including restricting the movement of machinery to or from resistance-compromised locations, strict monitoring of farms used for certified seed production, and strict regulations on planting certified seeds. Education drives pertaining to best management practices for weed-resistance detection and management is in its infancy in small countries in Central and South America, such as Colombia, as well as in similarly resource-limited rice-producing countries globally. Research and education efforts need to be strengthened across academia and various public and private sectors to empower farmers and improve productivity at the farm level. A major challenge in tropical regions is the continuity of crop growing seasons. Without the winter freeze to break the cycle of weed growth and kill a portion of the soil seedbank, the herbicide selection pressure in tropical regions is high, and the rate of resistance evolution is also high, considering the same pattern of herbicide use per cropping season. The adoption of intensive integrated weed management practices is critical, including the removal of weed escapes, prevention of weed seed production, crop rotation, and diversification of herbicide use.

4.3 Intraspecific competitiveness of quinclorac-susceptible and quinclorac-resistant junglerice

The question of whether resistance to herbicides impacts weediness is practically relevant. Different fitness outcomes have been reported in herbicide-resistant weeds. Quinclorac-resistant junglerice from Arkansas, USA, has not shown a fitness penalty (Penka, 2018; Velasquez and Roma-Burgos, 2024). Likewise, barnyard grass (Echinochloa crus-galli), resistant to propanil or clomazone in mid-Southern USA, did not exhibit fitness penalty (Bagavathiannan et al., 2011). Brazilian researchers reported similar competitiveness of quinclorac-resistant and quinclorac-susceptible Echinochloa spp. to rice ‘BRS Pelota’ (Tironi et al., 2009). The lack of fitness penalty associated with herbicide resistance evolution has been documented in other cases. For example, wild turnip (Brassica rapa) harboring a glyphosate transgene and a non-transgenic ALS resistance gene from the crop relative canola (Brassica napus) does not exhibit a fitness penalty (Tillería et al., 2023). In fact, some mechanisms of resistance to a particular herbicide may confer a fitness advantage. Such is the case of glyphosate-resistant junglerice that produced 57% more biomass and 10% more seed mass than the susceptible counterpart at the 50:50 proportion (Shrestha et al., 2018).

Information concerning fitness penalty for evolving resistance to some herbicide modes of action in various weed genera is slowly accumulating. Seed production has been reduced 5% in glyphosate-resistant goosegrass (Eleusine indica L.) and 60% in ALS-resistant annual bluegrass (Poa annua L.) (Han et al., 2017; Tseng et al., 2019). Likewise, dicamba-resistant kochia (Bassia scoparia) harboring a mutation (G73N) in the IAA16 gene produced 80%–90% less shoot biomass and seeds (Wu et al., 2021). IAA16 is a transcriptional repressor of auxin response factors, a member of the complex of auxin response repressor proteins AUX/IAA. The degradation of this complex is mediated by the binding of dicamba and the SCF-type ubiquitin ligase complex, which releases the auxin response genes. Therefore, resistance to herbicides may or may not cause a fitness penalty depending on the mechanism(s) endowing resistance.

The quinclorac-resistant and quinclorac-susceptible populations used in the competition experiments were collected from the same region. This pairing was intentional, assuming that these are genomically most similar compared to populations from other regions. These populations are also morphologically and phenologically the same. Thus, we can attribute (with high confidence) the difference in their competitive ability to physiological consequences related to the resistance trait. Overall, the quinclorac-resistant junglerice grew bigger in monoculture than in competition with its susceptible counterpart, whereas quinclorac-susceptible junglerice exhibited higher growth in competition with resistant plants compared to the susceptible monoculture. This suggests that to some extent, the resistant population is at a disadvantage in competition. However, this response was not consistent in the second run of experimentation, and the indices evaluated do not detect this variation at the 50:50 proportion. Based on the data thus far, we could say that high resistance to quinclorac may reduce the competitiveness of junglerice under certain circumstances. This is consistent with the literature, where some cases of fitness penalties have been reported. Further studies should clarify this behavior and would generate more useful information, such as the effect on growth and development, weed seed production, seed dormancy, and emergence patterns.

4.4 Interspecific competitiveness of hybrid and inbred rice to quinclorac-resistant and quinclorac-susceptible junglerice

Overall, junglerice (R or S) was more competitive than rice (inbred or hybrid). Hybrid rice and inbred rice exhibit similar competitiveness with junglerice; however, less biomass accumulation was observed in the quinclorac-resistant junglerice competing with hybrid rice compared to inbred rice. Although hybrid rice did not exhibit the expected remarkable vigor against susceptible junglerice, hybrid rice exhibited the potential to suppress biomass accumulation (up to −21% relative advantage compared to inbred) and leaf area development (up to −26% relative advantage compared to inbred) of the quinclorac-resistant junglerice compared to inbred rice. This has been observed in previous studies; for example, the hybrid rice Mestiso 21 could reduce saramollagrass competition not only by reducing weed growth but also by reducing 30%–35% of saramollagrass inflorescence biomass more than did the inbred rice IR64 (Awan et al., 2018). Likewise, the hybrid rice CLXL8 incurred less yield losses (6% to 35%) from weedy rice competition compared to the inbred rice ‘CL161’ (14% to 45%) (Shivrain et al., 2009).

There is a lack of information about the competition dynamics of hybrid rice against resistant weeds; therefore, the fact that the hybrid rice we tested showed potential to suppress resistant junglerice is a novel finding that justifies follow-up research. The mechanism(s) of interference might also involve allelopathic interaction. The competitive performance of the inbred rice also highlights the breeders’ efforts to strengthen the selection for weed-competitive cultivars for the region.

Rice yield losses due to junglerice interference are wide-ranging. Environmental factors aside, the major biological factors modifying weed interference outcomes are weed species, level of infestation, duration of interference, and crop variety. Studies in Palmira, Colombia, 20 years ago showed that competition of Latin America and Caribbean rice cultivars (270 seeds m⁻²) with junglerice (40 seeds m⁻²) became significant 40 days after emergence, causing up to 50% reduction of grain yield at 90-day competition duration. This correlated (r = 0.62) with an average of 35% rice biomass reduction (Fischer et al., 1997). In other words, a 35% rice biomass reduction has a 62% likelihood of reducing rice yield by 50%. In other studies, early weed biomass accumulation (36 days after emergence) has a 47% probability of reducing rice yield by 44% (de Vida et al., 2006). These previous studies were conducted with inbred rice cultivars. In the replacement series experiments reported in this current research, the average biomass reduction across plant proportions was 24% for hybrid rice and 18.5% for inbred rice. Therefore, the competitiveness of both hybrid and inbred rice has increased after years of breeding, thereby reducing the potential yield losses. We can also speculate that some contemporary inbred rice varieties may incur lesser yield losses from weed competition than hybrid rice. This idea can be explored in future research.

5 Conclusion

The auxin-herbicide-resistant junglerice is potentially less competitive than the susceptible junglerice. The hybrid and inbred rice exhibit similar competitiveness with quinclorac-susceptible junglerice. Hybrid rice reduces the biomass accumulation and leaf area development of quinclorac-resistant junglerice.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Author contributions

JV: Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. DR: Data curation, Formal Analysis, Investigation, Methodology, Validation, Visualization, Writing – original draft, Writing – review & editing. MA: Conceptualization, Funding acquisition, Methodology, Project administration, Resources, Writing – review & editing. EG: Conceptualization, Funding acquisition, Methodology, Project administration, Resources, Writing – review & editing. YS: Conceptualization, Funding acquisition, Investigation, Methodology, Project administration, Resources, Writing – review & editing. GP: Conceptualization, Funding acquisition, Investigation, Methodology, Project administration, Resources, Writing – original draft, Writing – review & editing. NR-B: Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing.

Funding

The author(s) declared that financial support was received for this work and/or its publication. Financial support for this research was provided by the Global Rice Research Foundation (Global Rice Leadership award), University of Arkansas, The International Center for Tropical Agriculture (CIAT), The Latin American Fund for Irrigated Rice (FLAR), and Universidad Nacional de Colombia (Project code 60318).

Acknowledgments

The authors thank all the participants who participated directly or indirectly in the realization of this project, including the team from CIAT and FLAR (Maribel Cruz, Marcela Pineda, Juanita Torres, Cristian Herrera, Leydi Sandoval, and many others), the team from UNAL, Paula Virguez for helping in the map design and data curation, and Camila Alvarez for collecting the first batch of seeds.

Conflict of interest

The authors declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The reviewer ASG declared a shared affiliation with the author(s) JV, DR, NR-B to the handling editor at the time of review.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fagro.2025.1694918/full#supplementary-material

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