Evaluation of Virulence of Xanthomonas oryzae pv. oryzae against Rice Genotypes

Bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae, arguably is the most important disease of rice (Oryza sativa L.) worldwide due to its growing concern, wide spread and destructive nature and lack of understanding its control. The present study was carried out for screening of rice germplasm against X. oryzae pv. oryzae and determination of phenolic contents regarding the physiology and biochemistry of diseased plants. Out of the 40 cultivars tested none of the variety showed significantly resistant response against the virulence of pathogen; only six were found moderately resistant, eight were graded as moderately susceptible, while 19 showed susceptible and six as highly susceptible response. Significantly highest disease severity (68.08%) was recorded on TN1, whereas minimum (11.92%) was calculated on Mehak-2006. All the basmati varieties were found to be susceptible to highly susceptible against the disease and showed disease severity within a range of (51.21 to 65.05%), while the KSK genotypes presented (32.62 to 45.68%) disease severity. The total phenolics concentration significantly varied in response to treatment and showed negative correlation with the resistance of the variety. The highest phenolics compounds (183.42 mg 100(-1)) were produced in Mehak-2006, while the phenolics of TN1 were not in the range of gallic acid standard. It appeared that resistant varieties showed higher concentration of phenolics than the susceptible ones, which played important role in reducing the disease severity. Thus, the study suggests that the exploitation of secondary metabolites in breeding programs and integrated management strategies could open the avenues to avoid future disease epidemics. (C) 2015 Friends Science Publishers