Comparative Analysis of Biochemical and Stomatal Characteristics in Resistant and Susceptible Varieties of Pomegranate (Punica granatum L.) Against Bacterial Blight

Stomata act as main entry points for further spreading of bacterial blight which is a highly dangerous disease of pomegranate. Studies were conducted on total chlorophyll, chlorophyll a, chlorophyll b, total carotenoids, stomatal length, width, frequency and index in leaves of pomegaranate in response to bacterial blight caused by Xanthomonas citri pv. punicae. Five pomegranate varieties—‘Mridula’, ‘Jyoti’, ‘Jodhpur Red’, ‘Bhagwa’ and ‘Ganesh’—were screened for bacterial blight resistance under natural conditions in northwestern India. The varieties ‘Mridula’, ‘Jyoti’, ‘Jodhpur Red’, and ‘Bhagwa’ were rated as moderately resistant, whereas ‘Ganesh’ was rated as moderately susceptible on the basis of percent disease index (PDI) of pomegranate leaves. Total chlorophyll, chlorophyll a, chlorophyll b, and total carotenoids were lower in moderately susceptible Ganesh variety as compared to the moderately resistant varieties ‘Mridula’, ‘Jyoti’, ‘Jodhpur Red’, and ‘Bhagwa’ of pomegranate. Stomatal length, width, frequency and index were highest in moderately susceptible ‘Ganesh’ variety as compared to the moderately resistant varieties ‘Mridula’, ‘Jyoti’, ‘Jodhpur Red’ and ‘Bhagwa’ of pomegranate. A significant negative correlation has been observed between the PDI (leaves) and total chlorophylls, chlorophyll a, chlorophyll b, and total carotenoids. However, significant positive correlation has been observed between PDI (leaves) and stomatal characteristics viz., stomatal length, stomatal width, stomatal frequency and stomatal index. Present study helps to identify resistant varieties, optimize chemical applications and understand the active immunity of plant, directly benefiting both researchers and agricultural workers.