Serological studies on genotypic relationship among rice varieties.

Three rice cultivars, Taichung (n) 1 (indica type) and Taichung 65 and Nakamura (japonica types), were used to immunize rabbits to obtain antisera. Another 37 rice cultivars from various countries were used as antigen sources for studies of antigen-antibody reactions between the two groups of cultivars. When the antisera incited by immunization with seed protein of japonica type cultivars were titred with antigens from known japonica type cultivars, a positive precip itation reaction occured, but no reaction was obtained with antigens from indica type cultivars. In a few cases antigens from a cultivar reacted with both indica and japonica type antisera. The antigens from these intermediate types may have had reating sites for both types of antisera or the antigen complex may have contained two antigen types, one for indica and one for japonica. These intermediate cultivars that appeared to have both indica and japonica antigens may have been selected from japonica x indica crosses. The gel-diffusion technique showed rice cultivars within indica or within japonica could be grouped into subgroups on the basis of the pattern of their precipitated bands. There was no relationship among American rice cultivar for grain length, i.e., long, medium or short japonica and indica type. The serological method would be useful for assigning rice cultivars to japonica or indica types and perhaps to subgroups within these types. Whether it would be useful to rice breeders to pre dictdesirable crosses must await additional study,