Abstract
Eight different isolates of Xanthomonas oryzae pv. oryzae (Xoo) procured from International Rice Research Institute (IRRI) Manila, Philippine were subjected to pathogencity test to check virulence on three basmati rice varieties in order to find out the source of resistance against Bacterial blight and to pick the most resistant and susceptible varieties.
Rice nursery was grown in the glass house and pathogenicity of each strain was tested on 4 week, 8 week and 12-week-old rice plants by using clipping method of artificial inoculation, in which five plants successively inoculated, after dipping the scissors in the bacterial suspension. A control of each variety was also maintained, for this, scissors dipped in sterile water was used for clipping off leaves. The symptom development was rated by counted lesion number, size and progress of blightening, which indicated the resistance of particular variety against particular strain.
It was evident from the results that all the three rice varieties were susceptible to Xoo but Super basmati was highly susceptible to all the exotic strains of Xoo with maximum percentage disease incidence (89.5%) for PXO 340 at the seedling stage (4 week), with 84.54% at maximum tillering stage and with 56.21% for PXO 61 at leaf flag stage. On the other hand Basmati 2000 was most resistant variety at all the two growth stages and susceptible at maximum tillering stage for PXO 280, with maximum percentage disease incidence (75.96%) and PXO 340 with 71.53%. The reaction of eight different strains of Xoo was variable against the Basmati 385. At seedling stage, it showed susceptibility against PXO 61 with maximum percentage disease incidence 65.33%, for PXO 339 with 58,18% at maximum tillering stage and with highest rate of maximum percentage disease incidence i.e. 75.68% for PXO 341 at leaf flag stage. The reaction of a bacterial strain was variable to different rice varieties, the reaction of different bacterial strains was also found variable against the same rice-varieties.