GENETICS OF RESISTANCE TO BACTERIAL BLIGHT IN RICE (ORYZA SATIVA L.)

Abstract

The mode of inheritanceand allelicrelationship amonggenes forresistancetofivedifferent races of bacterial blight (Xanthomonas campestris pv oryzae) in three cultivars, resistant at all growth stages, was studied. The Ft and F2 progenies from crosses of the test cultivars withTN1, when inoculated at seedling, maximum tillering and flowering stages, revealed that two recessive genes control resistance in them. Tests for allelism indicated that one of the genes is xa-S, which confers resistance to races I, II and III at the seedling stage. The other gene confers resistance at seedling stage to races IV and VI. This newly identified recessive gene segregates independently of Xa-3, Xa-4, Xa·7 and Xa-l0 but is linked to xa-S with the crossover value of about 9.68%. Thus the cultivars Long Grain, Kali Mekri 77-5, and Aus 295 have a second recessive gene besides xa-S, which may be allelic to xa-13.