Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/22/2003
Publication Date: 6/10/2003
Citation: Foley, M.E., Gu, X., Nadella, D. 2003. Developing weedy rice for map-based cloning of seed dormancy genes. In The Biology of Seeds: Recent Research Advances. (eds. Nicolas, G., Bradford, K.J., Come, D., and Pritchard, H.W.) CAB International. 2003. p. 151-159. Interpretive Summary: Although seed dormancy is a key characteristic of weedy plants, mechanism governing seed dormancy are unknown. To elucidate mechanism governing seed dormancy in weedy grasses, we must clone and characterize genes that directly regulate this trait. Currently, it is not possible to map-base clone dormancy genes from well characterized species like wild oat because of the large genome size. Thus, we are developing rice, a species with a relatively small genome size, to map-base clone dormancy genes. As a first step, we have cross-pollinated dormant weedy strains of Asian rice with nondormant domesticated strains to develop populations segregating for dormancy. In this contribution, we report on the classical genetic attribute like heritability associated with several populations segregating for hull- and pericarp/testa-imposed dormancy.
Technical Abstract: Seed dormancy in selected O. sativa weedy and cultivated strains and O. glaberrima cultivars was imposed by the seed coverings, i.e., hull and pericarp/testa. Genotypes with a higher level or a much longer duration of seed covering-imposed dormancy were present in weedy rice strains. To investigate the inheritance of seed dormancy weedy strains `LD' and `SS18-2' and nondormant varieties `CO39' and `WYJ' were chosen to develop F1 and F2 generations. Strains `SS18-2' had strong hull- and weak pericarp/testa-imposed dormancy and a long duration of seed dormancy. Strain `LD' had strong pericarp/testa-imposed dormancy. The average degree of dominance for seed germination was greater than 0.7 when non-afterripened seeds were evaluated. Broad-sense heritability (h2b) was lower for germination of non-afterripened seed (0.64 to 0.76) and highest for germination of partially afterripened seeds at 20 days after harvest (DAH) (0.85 to 0.95) in all the crosses. At least three genes regulating germinability at 0 and 20 DAH were detected in the `N22'- and `SS18-2'-derived F2 populations, respectively. This research demonstrates that weedy strains of rice provide ideal gene resources to elucidate mechanisms of dormancy and to improve resistance to preharvest sprouting.