Biochemical basis of resistance in rice against Bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae

Background: Bacterial Leaf Blight (BLB) is the most devastating disease of rice. This disease can reduce grain production by 20-50% and yield by 25%. The disease is widespread in Asia, United State, Latin America and Australia. In Pakistan, it is reported from all rice growing areas and it is increasing its area year by year. All famous Pakistan’s Basmati varieties are susceptible to BLB disease. The most economical way of controlling disease is to produce resistant varieties. Many different compounds are involved in resistance mechanism in host including phenolic compounds.Methods: Plants inoculated with Xanthomonas oryzae pv. oryzae isolates i.e. 78.3 and 2.2 caused disease on all varieties were selected for investigation of phenolic compound. Randomized complete block design was used in field for inoculation and leaf collections for phenolic compounds determination. Data was phenolic compounds were analyzed through factorial ANOVA.Results: The response of four varieties was different when inoculated with BLB isolate 2.2. Basmati 2000 variety of rice produced maximum amount of phenolic compounds after one week of inoculation of bacterial isolate 2.2 while the minimum total phenols were found in basmati 385 at 0 hrs. of inoculation (before inoculation). Xoo isolate 78.3 produced maximum phenolic compounds after 2 weeks in Basmati 2000.Conclusions: Biochemical resistance due to high phenolic contents in Basmati-385 and Basmati-2000 is suggested. High phenol production may be due to loss of virulence in bacterial isolates. Both 78.3 and 2.2 Xoo isolates are significantly different in producing total phenols in all the varieties tested