Decoding phenotypic signatures of Cylas formicarius Fab. resistance in a global sweetpotato (Ipomoea batatas [L.] Lam.) germplasm collection

Alfredo Morales^1,2*Peiyong Ma²ZhaoDong Jia²Dania Rodríguez¹Iván Javier Pastrana Vargas³Rosa Elena González¹Osmany Molina¹Alay Jiménez¹Yuniel Rodríguez¹Lilian Morales¹Yoel Beovides¹Orelvis Portal⁴Xiaofeng Bian^2*

• ¹Research Institute of Tropical Roots and Tuber Crops, Santa Clara, Cuba
• ²Jiangsu Academy of Agricultural Sciences, Nanjing, China
• ³Faculty of Agricultural Sciences, Universidad de Córdoba, Córdoba, Colombia
• ⁴Universidad Central "Marta Abreu" de Las Villas, Santa Clara, Cuba

Sweetpotato (Ipomoea batatas [L.] Lam.) is a critical global food crop vulnerable to devastating yield losses caused by the sweetpotato weevil (Cylas formicarius), particularly in tropical regions where chemical control is often impractical. Despite decades of research, breeding programs have struggled to develop stable resistance, in part due to insufficient characterization of phenotypic markers across diverse germplasm. Here, we evaluated 731 accessions from Cuba's national sweetpotato collection enriched with global varieties to identify morphological traits associated with natural resistance to C. formicarius. Field and laboratory assessments revealed that only 6.5% of accessions demonstrated resistance (<10% infestation), while 80% were susceptible. Weak to moderate correlations linked resistance to smoother root surfaces (r = 0.31), lighter flesh pigmentation (r = -0.38), and, most significantly, deeper tuberization (r = -0.72). Six Cuban genotypes combined agronomic viability (yield >10 t ha⁻¹) with resistance, employing distinct strategies: five relied on deep tuberization as a physical escape mechanism, while INIVIT B-25 exhibited shallow tuberization (4.53 cm) yet maintained resistance, suggesting biochemical defenses. Under controlled infestation, INIVIT B-2022 showed the strongest antibiosis, suppressing adult emergence to just 2 individuals. Our results decode key phenotypic signatures of weevil resistance and provide immediately actionable traits for Caribbean breeding programs, while highlighting the need for molecular studies to uncover complementary mechanisms.