Identification Of QTL And Interaction Analysis For Degenerated Spilelet On The Top Of The Panicle In Rice

Degenerated spikelet is referred as that the spikelet on the top of panicle degenerates due to the spike development dysplasia. The phenomenon of degenerated spikelet is very common in rice. Genetic studies on rice degenerated spikelet of top panicle has rarely been reported. Indica variety 9311 is known as an elite restorer line of super-hybrid rice in China, which have big panicles with more grains and high yield. But it exists defect of degenerated spikelet. In the present study in our lab, we aimed to identify of QTL for degenerated spikelet and related traits in rice and to estimate its genetic effect, using the introgression lines derived from Japonica variety Nipponbare and 9311. The results will provide important basis for explaining generation mechanism of degenerated spikelet and molecular genetic manipulation of rice yield. The main results are as follows:1. Degenerated spikelet and related traits of 9311, CSSLs102, F₂ and SF₂ (SF₃) populations that were derived from CSSLs102/9311 were evaluated in Wuhan and Hainan. Both of the primary panicle degenerated spikelet rate and maximum degenerated spikelet rate all showed CSSLs102>SF₂ (SF₃)>9311 in the two test sites. The degree of the degenerated spikelet on either parents or the progenies all showed more seriously in Hainan than that in Wuhan. The primary panicle degenerated spikelet rate and maximum degenerated spikelet rate were significantly correlated with primary panicle length. The degree of the degeneration of spikelet was not related with the heading date in Hainan.2. By whole genomic scanning for the target introgression lines (CSSLs102) and F₂ populations using 165 polymorphic SSR markers by extreme DNA bulked segregant analysis, we preliminarily located chromosomal region or QTL on chromosome 3 and 9, which may be related with the degenerated spikelet.3. As using SF₃ lines to detecte QTL on chromosome 3, it was found that a QTL in the interval of RM14795-RM14803 controlled the primary panicle length, heading date, the number of primary branches and second branches simultaneously. A QTL controlled the primary panicle degenerated spikelet rate and the maximum degenerated spikelet rate were located in the interval of RM14820-RM14859, with contribution of 11.1% and 9.5% to the phenotypic variance respectively.4. Interaction analysis was performed on the two QTL of chromosome 3 and 9 using F₃ populations derived from the seletcted SF₂, the result indicated that the dominant effect of gene controlled the spikelet degeneration on chromosome 3 was larger than those on chromosome 9. The significant dominant X dominant interactions between the two loci influenced the rice degenerated spikelet.