Breeding for resistance to Piricularia Oryzae in rice (O. Sativa)

Abstract

The disease,piricularia, was first noticed in Madras when it appeared in an epidemic form attacking a particular variety of rice,korangusamba, in portions of the Tanjore district. The studies on the fungus by the Mycologist had shown that there was a wide range of susceptibility of rice varieties to the disease, some remaining practically immune while varieties like the Tanjore one showing 70 to 80 per cent. incidence. Work of breeding forms resistant topiricularia was undertaken by the Paddy Specialist in 1926. Two of the strains evolved by him, GEB. 24 and Co. 4 which were determined to be highly resistant, were crossed with the susceptible variety from Tanjore. The inheritance of disease resistance appeared to be simple in the cross GEB. 24× korangusamba and more complicated in the cross Co. 4 × korangusamba. In the former cross disease-free selections from F₃ onwards bred pure for freedom and two of these after two years’ trial both at Coimbatore and Aduturai have been found to give a big increase in yield over the susceptible variety (10–50 per cent.), the increase being more or less according as the susceptible variety gets the infection or not. Selections from the other cross are still under study and appear even more promising than the first. We are indebted to the Superintendent, Agricultural Research Station, Aduturai, for the figures of yield trials conducted there.