| It is commonly suggested that rice earliness is a recessive trait controlled by one or two major genes or a quantitative trait controlled by minor polygenes in rice,though there are a few reports on dominant earliness controlled by dominant gene.So far,there are only five earliness genes reported ,in which there are four dominant genes and one recessive gene. In this study ,the earliness trait of new preserver line D64B is carefully researched, the result is as follow:1) The earliness trait of preserver line D64B is a completely dominant trait influenced by genetic backgroud of the indica parent, the F1 progenies from D64B×D62B and D64B× E You 540and D64B×Zhen Shan 97 so on,shared the same heading date as D64B . but the F1 from D64Bx Shu Hui 527 (late-maturing varieties) and so on,shared the same heading date one another and had the heading date between two parents ,which was earlier than mid-parent value,when D64B crossed with the medium- or late-maturing Japonica rice such as Zhong Hua 15 and Jiang Shu Geng Luo,some of F1 progenies had longer heading date than their both parents,some of F1 progenies had longer heading date than mid-parent value.2)The earliness trait of D64A conforms to that of D64B.D64A was bred by D64B . Making D64A cross with mid-maturing D62B,their F1 shared the same heading date as D64B,but making D64A cross with late-maturing Shu Hui 527 and so on , the heading dates of their F1 generations,earlier than the mid-parent value.are close to one another.3) Sterile cytoplast had no effect on the earliness of D64B .The F1 ,which from D64B crossed with sterile line G46A and Zhen Shan 97A and so on,shared the same heading date as D64B.4) The earliness trait of D64B was controlled by one dominant major gene . Significant segregation of heading date was observed in the F2 populations .which from D64B×Shu Hui 527 and D64B×Shu Hui 361 and D64B×II-32B and D64B×D62B and Shu Hui 527×D64B,and the Bd populations,which from D64B×Shu Hui 527.The segregation ratio of early to late heading plants in the F2 populations and BC1 correspondingly fitted the ratio of 3:1 and 1:1.To identify the loci of the dominant major gene,the near isogenic pools of earliness andlateness were constructed from the F2 population of D64B×Shu Hui 527 and the polymorphisms existed in the two pools was screened by SSR markers .As a result,SSR marker RM279 were found linked to the dominant earliness gene in D64B,the gene was located on the top arm of the second chromosome in rice and its heredity distance to RM279 was 18.8 cM.Because of the first discovery.the earliness gene was named as Ef-3(t).5) The earliness gene harbored in D64B harmonizes the contradication between earliness and fertility on heredity. Making D64B cross with the parent which has farther kin,its gene has more obviously dominant effect on the earliness,meanwhile ,the farther kin of parents makes for the high yield of their progenies.Because it is easy for the earliness gene harbored in D64B to introduce into other parents to breed new male-sterile line and preserver line and restorer line, D64B is a valuable earliness genetic resource.On the one hand ,the discovery and utilization of single gene harbored in D64B can facilitate resolving contradication between earliness and fertility in earliness rice production,one the other hand , it can also make for breeding early-maturing intersubspecific hybrid rice to overcome the late maturity problem that occurs in most subspecific hybrids.Therefore,as a new genetic resource of dominant earliness.D64B has splendid future in rice breeding.Making D64B cross with E You 540,early generation stabilization variety,their F1 shared the same heading date as D64B,the earliness of D64B performed complete dominance.this indicated that the heterosis on earliness hybrid rice might be fixed by the rice with early generation stabilization,which pioneered a new approach for the making use of earliness hybrid rice.With D64B backing cross s... |
