Utilization of F_1 weakness gene for breeding of rice varieties which prevent gene pollution

近年来，具有独特的色、香等特性的水稻品种唤醒了育种者的兴趣，以满足主食以外的各种需求。然而，当与普通大米混合时，这些特性会降低谷物质量，而且这些特殊品种往往表现出“杂草”习性。1)对一批红米品种的农艺性状和化学性状进行了综合评价，从中选出2个品种进行育种。2)当普通水稻植株Arg与红稻自然杂交时，一种导致F_1代不活或衰弱的遗传系统被证明是有效的。由于大多数日本品种携带一个互补的F_1弱势基因HWC-2，因此通过回交将另一个基因HWC-1导入红稻品种Soja。3)蒙特卡罗计算机模拟表明，该遗传系统对通过花粉的基因污染是有效的，但对通过种子或植物的基因污染无效。4)为了在花粉竞争研究中区分来自不同品种的花粉，获得了与红稻Soja特异的花粉多肽具有亲和力的抗体。5)红米品种不一定杂草丛生。然而，F2研究和选择实验表明，杂草红米在红白非杂草类型的杂交后代中可以分离，这是因为两个控制红粒颜色的基因分别与两个起互补作用的碎粒基因连锁。

Recently, rice varieties having particular characteristics of color, fragrance, etc. awaken the interests of breeders to meet various needs other than staple food. Those traits, however, lower the grain quality when mixed with ordinary rice, and moreover those particular varieties often show "weedy" habit. The present project aimed at practical breeding of a red-rice variety which is good for coloring agent of alcohol but does not cause genetic contamination of ordinary rice fields.1) A number of red-rice varieties were evaluated regarding agronomic as well as chemical traits, and two were selected for breeding program. 2) A genetic system to cause inviability or weakness of F_1 hybrid was experted to work when ordinary rice plants arg naturally crossed with red rice. Since most Japanese cultivars carry one of the complementary F_1 weakness genes Hwc-2, introduction of another gene Hwc-1 into a selected red-rice variety "Soja" was carried out by backcrossing. 3) Monte Carlo computer simulation showed that this genetic system is effective for gene contamination through pollens, but not for gene contamination through seeds or plants. 4) In an attempt to discriminate pollens derived from different varieties in a pollen competition study, antibodies was obtained which have affinity to pollen polypeptides specific to red-rice "Soja". 5) Red-rice varieties are not necessarily weedy. F_2 study and selection experiment, however, indicated that weedy red rice could be segregated in the hybrid progeny between red and white non-weedy types, because two genes for red grain color are linked with two shattering genes, respectively, which work in a complementary manner.