PATTERN OF INHERITANCE OF RESISTANCE TO BACTERIAL LEAF STREAK IN RICE CULTIVARS

Genetic pattern of inheritance of resistance to bacterial leaf streak (BLS), a bacterial disease caused by Xanthomonas compestris pv. Oryzicola was studied under artificial inoculation conditions in parents, F1 Plants, F2 population and F3 progenies in five cross combinations involving two indian rice cultivars viz. Bogzira 1 (BJ.1, resistant to BLS), NC 1281 (resistant) and one Philippine rice, Pankaj (Susceptible to BLS) using the bacterial isolate grown on semi synthetic potato-sucrosc-agar medium. A simple and sure method was adopted for inoculation. The plants were scored for disease reaction and are classified as resistant (R) or susceptible (S) on the basis of colour, length, number and mode of distribution of lesions on the leaves. A cross between NC 128i and B.J.1 resulted in 12R (NC 1281 Type); 3MR (BJ.1 type) and 1S segregates. A ratio of 13:1 was realized from crosses involving resistant (R)/moderately resistant (MR) and susceptible (S) varieties and their reciprocal crosses. The appearance of susceptible class in F, and F, of a cross between NC 1281 and BJ.1 confirmed that B.J.1, till now considered to be resistant, is found to be moderately resistant (MR) to BLS, bearing leaves with long and unrestricted light brown coloured lesions. Segregation of F3 lines in to OR: IS, IR: 3S, 3R: IS, 3R:13S and IR: OS with non-significant chi square values in crosses-NC 1281 x Pankaj, Pankaj x NC 1281, B.J.1 x Pankaj and Pankaj x B.J.1 confirmed that resistance to BLS was governed by epistatic genes. Segregation of F3 of NC 1281 x B.J. 1 into IR: OMR: OS (true breeding R), OR: IMR: OS (true breeding MR), 12R:3 MR: IS, 3R: IMR: OS, 3R:OMR: IS, OR: 3 MR: IS and OR: O MR: IS (true breeding susceptible) ratio with chi square value of 2.26 further justified in classifying BJ.1 as moderately resistant variety. Success of resistance breeding programme depends on the basic knowledge accumulated about the genetics of resistance.