Copper-Streptocycline Application Modulates Pomegranate (Punica granatum L.) Secondary Metabolism and Antioxidant Pathways against Xanthomonas axonopodis pv. punicae-induced Bacterial Blight

Ghulam Mustafa¹Ishtiaq A Rajwana¹Hafiz Nazar Faried¹Syed Atif Hasan Naqvi²Uzman Khalil³Muhammad Umer Iqbal¹Mysoon M Al-Ansari⁴Mohamed S Elshikh⁴Hakim Manghwar^5*Fen Liu⁶

• ¹Muhammad Nawaz Shareef University of Agriculture, Multan, Pakistan
• ²Bahauddin Zakariya University, Multan, Pakistan
• ³University of Florida, Gainesville, United States
• ⁴King Saud University, Riyadh, Saudi Arabia
• ⁵Lushan Botanical Garden (CAS), Jiujiang, China
• ⁶Lushan Botanical Garden Jiangxi Province and Chinese Academy of Sciences, Jiujiang, China

Bacterial blight of pomegranate (Punica granatum L.), caused by Xanthomonas axonopodis pv. punicae (Xap), significantly affects production and fruit quality. This study investigated the effects of various bactericides on disease intensity and fruit quality in pomegranate orchards. Field experiments were conducted for three consecutive seasons with application of six bactericides at 15-day intervals from May to July on Sindhuri, Kalehar, and Sava cultivars in a randomized complete block design. The results showed that the treatment of copper oxychloride (3000 ppm) combined with streptocycline (500 ppm) (T7) was the most effective in reducing disease intensity. The Sindhuri cultivar showed the lowest mean disease incidence on the leaves (3.51%), fruits (3.88%), twigs (0.58%), and trees (3.59%) with T7 application. Disease severity percentages were also observed to be the lowest in Sindhuri on leaves (0.56%), fruits (0.79%), twigs (0.70%), and trees (1.92%). The highest mean disease reduction, such that 77.63% on leaves, 79.76% on fruits, 76.10% on twigs, and 76.90% on whole trees, was observed in Sindhuri plants treated with T7, and these values were significantly higher than those of the control and other less effective treatments.. The highest mean values for marketable yield (89.60 kg), fruit weight (245 g), and hundred arils weight (43.30 g) were achieved under T7 treatment with marketable yield observed in Sindhuri and hundred arils weight in Sava.. Additionally, T7 enhanced fruit biochemical attributes, with mean TSS (17.90 °Brix), pH (4.16), vitamin C (36.50 mg/100 mL), antioxidants (86.40% inhibition), TPC (445 mg GAE/100 mL), CAT (21.30 U/mg protein), and POD (1.35 U/mg protein). Sindhuri showed higher resistance to bacterial blight, followed by Kalehar and Sava. These findings highlight the potential of optimized copper-streptocycline application to mitigate bacterial blight caused by Xanthomonas axonopodis pv. punicae, enhance pomegranate yield and market quality, and reduce losses from orchard decline.