Division of Mycology and Plant Pathology and Division of Genetics, Indian Agricultural Research Institute, New Delhi
1Present address: Plant Pathology, S. V. Agricultural College, Tirupati (A.P.).
*Part of Ph.D. Thesis submitted by C.J. Moses to the P. G. School, IARI, New Delhi.
Studies on inheritance of bacterial blight resistance in rice were carried out in different donor parents, viz., IRRI 69/469, IRRI 70/470, BJI, Lacrosse × Zenith-Nira and Malagkit Sungsong against two isolates, XO10 and XO32 of the pathogen, Xanthomonas oryzae with the aim of determining the number of genes controlling resistance and their allelic relationship.
Resistance to isolate XO10 was found to be controlled by a single dominant gene in the varieties IRRI 69/469, IRRI 70/470, BJI and Lacrosse × Zenith-Nira. However, the expression of the genes in the latter two varieties was found to be suppressed by a dominant inhibitory gene. Two dominant complementary genes seemed to govern resistance in Malagkit Sungsong. The resistance genes in IRRI 69/469 and IRRI 70/470 appeared to be allelic. The varieties BJI and Lacrosse × Zenith-Nira had a common resistance gene while the two complementary genes offering resistance in Malagkit Sungsong were different from those of the other varieties.
Resistance to isolate XOS2 was governed by two dominant complementary genes one each from Malagkit Sungsong and IRRI 70/470. The genes involved were the same as those offering resistance to XO10. From this cross it was shown that strong resistance mechanisms could be assembled in the progeny by recombinations to the highly virulent isolates against which resistance donors are rarely found in the available germplasm
