Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 8, 2002
Publication Date: June 1, 2002
Citation: PINSON, S.R. SEMIDWARF BREEDING LINES WITH IMPROVED SEEDLING VIGOR DUE TO INTROGRESSED GENES. RICE TECHNICAL WORKING GROUP MEETING PROCEEDINGS. 2002. p. 62. Technical Abstract: Upon the release of the first semidwarf rice cultivars in the 1980's, it was apparent that the semidwarf rices, as a group, had less seedling vigor than previously grown taller cultivars. The predominant source for producing semidwarf cultivars throughout the world has been the sd1 gene. It is now known the original genetic source for sd1 that was used in the U.S. also contained a linked gene that reduced seedling vigor by limiting the length of mesocotyls and coleoptiles. Because selection for semidwarfism was generally stringently applied in early segregating generations, the unfavorable linkage between the sd1 gene and the gene limiting mesocotyl length was maintained so pervasively that all southern US semidwarf rice cultivars available today have short mesocotyls. In a previous gene-mapping study, Teqing, a cultivar from China, was found to contain a desired allele for mesocotyl elongation now favorably linked to the sd1 gene. This gene was not expressed, however, unless it was genetically combined with a complimentary gene on a different chromosome that is already contained in much of the US rice germplasm. An additional gene from Teqing was found to increase mesocotyl lengths when combined with the two complementary genes. Several progeny lines within the above- mentioned gene-mapping study were found to contain all three desired mesocotyl genes plus the sd1 gene. Five lines were selected for germplasm release because they contain the desired Teqing genes introgressed into a plant type which is agronomically suited for U.S. rice production. These germplasms are recommended for use as breeding parents to generate vigorous semidwarf rice cultivars.