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I. Research Notes Field reaction of different Lr genes to the Indian leaf rust races S. C. ANAND and K. S. BAINS Punjab Agricultural University, Ludhiana-India Among the three wheat rusts, leaf rust probably causes most widespread damage throughout whole of India. Most of the newly developed high yielding wheat varieties which carried some resistance to it are already getting heavily infected with new races and biotypes of leaf rust. Thus, there is great need to incorporate as many resistant genes as possible into our future commercial varieties. The first step was to identify different sources of resistance to various leaf rust races prevalent in India. A set of known Lr genes was obtained from Drs E.R. SEARS and D.R. KNOTT and was inoculated with a mixture of races comprising 77, 162A, 12, 162, 26 and 106. Since leaf rust does not appear in the seedling stage in India, the material was screened at the adult plant stage. The work was conducted at the Punjab Agricultural University, Ludhiana and mean of two year data has been presented in Table 1. As evident from Table 1, Lr1 gene from Malakof has shown high degree of resistance to leaf rust races and it was free from this disease for both the years. Wichita, the background under which it was transferred was heavily loaded with rust. Lr2 gene from Webster also showed resistance as a maximum of trace infection with resistant type of pustules was observed on this line. Lr21 allele from Carina, Lr23 allele from Brevit and Lr 2 allele from Loros gave moderate to high susceptibility to leaf rust. Thus, the Indian races of leaf rust also differentiate between different alleles of Lr 2 locus. Lr 3 gene from Mediterranean and Democrat does not impart any resistance under Indian conditions, and both of them showed light to moderate infection with susceptible pustules. Lr 9 gene from Transfer was completely free from the disease. This was tested under Chinese Spring background which had light infection of leaf rust. Lr 11 gene from Hussar was ineffective against prevalent Indian races of leaf rust. Thus, the present study brings out the importance of Lr 1 gene from Malakof and Lr 9 from Transfer which could be used effectively. The gene from Webster could also be useful but as Lr 2 is a complex locus, it may be difficult to handle in the breeding process. Among the other important genetic stocks, Napo 63, Gaboto and Sonora 64 were found to be susceptible. Crespo 63 and E 129 had trace infection, whereas, Frontana, Centeria, Rio Negro, Transac, Lerma Rojo 64A, E 4870-1 and E 8212 were found to be completely free from leaf rust. The number of resistant genes each one of these stocks carry is not known, however, they have been reported to be resistant at several locations. These stocks along with Lr 1 and Lr 9 genes should be able to provide sufficient protection against leaf rust in India and should be extensively used in wheat breeding programme. (Received August 5, 1972) |