Study on inheritance of huge root in radish 'Sakurajima Daikon'

樱岛萝卜是世界上最大的萝卜。在鹿儿岛樱岛山附近，只有11名当地农民在经营。他们每个人都在自己的小块土地上种植这种品种，生产自己的种子。这个品种的基因库被认为是非常小的。另一方面，萝卜有很强的近交抑制，只要连续3次自交就能产生非常小的、虚弱的植株。本研究的目的是阐明该品种在基因库较小的情况下保持巨大的机制。每个农民都有自己的种植和播种方法。他们从种群中选择“雌性(F)”、“雄性(M)”及其中间类型，这些植物是开放授粉的，用于播种。从F和中间型采集的种子在这里种植，然后判断幼苗的“性别”类型，以便授粉。在1999年和2000年，它们进行了自花授粉和异花授粉，然后在接下来的几年里收获了这些植物。在第一代，自交群体的产量低于对照，而杂交群体的产量高于对照。但在第二代，F型自交群体的产量降低了一半，而M型自交群体的产量没有降低，而两者杂交中的一个则提高了产量。F型和M型的自交群体都产生了“性型”的变异。樱岛白鹭被认为是一个异种种群，M型可能是种群活力的一个因素。寻找与“性”类型相关的DNA标记，以阐明保持“性”的机制。

'Sakurajima Daikon' is the biggest radish in the world. It is maintained only by 11 local farmers around Mt. Sakurajima, Kagoshima. Each of them maintains this cultivar in his small field, producing his own seeds. The gene pool of this cultivar is considered to be very small. On the other hand, radish has strong inbreeding depression which produces very small, feeble plants only by 3 successive selfings. The purpose of this research was to clarify the mechanism of hugeness maintaining in this cultivar which has only a small gene pool.Each farmer has his own growing and seeding method. They select "Female(F)" , "Male(M)" and their intermediate type from their population, and these plants are open-pollinated for seeding. The seeds collected from F and the intermediate type were used and planted here, and the "sex" type of the seedlings were judged for pollination later. In 1999 and 2000 they were self- and cross-pollinated, and then the plants were harvested in the following years.In the first generation, selfed population showed lower yield than the controlof the farmer's original population, while crossed population showed higher yield. However, in the second generation, the selfed population of F type reduced the yield to a half, and that of M type did not reduce the yield, while crossed one of the both increased it.Selfed populations of both F and M type produced a variation of "sex type".'Sakurajima Daikon' is considered to be a heterogeneous population, and M type might be a factor of vigor in the population. DNA markers related to the "sex" type will be searched to clarify the machanism of hughness maintaining.