Genetic Mapping Of QTLs For Leaf Chlorophyll Content And Chlorophyll Degradation In Rice

In this study, a recombinant inbred (RI) population derived from the cross between an indica variety, IR24, and a japonica variety, Asominori and its molecular linkage map consisting of 289 RFLP markers through composite interval mapping analysis (CIM) were used to map quantitative trait loci (QTLs) controlling leaf chlorophyll content (LCC) and chlorophyll degradation at four different developmental stages (seedling, tillering, heading and maturity stage) of rice. The main obtained results were summarized as follows:1. A total of fifteen QTLs associated with LCC were detected from seedling to maturity stage, which included two QTLs at seeding stages, five QTLs at tillering stages, four QTLs at heading stage, and four QTLs at maturity stage, respectively. And these QTLs were distributed on most rice chromosomes except for chromosome 5, 7 and 11, which explained for 7.26%～20.06% of phenotypic variations. In addition, most QTLs were found to be located in different regions, showing they had the time-space specific expression. However, each QTL for LCC at seedling(qSLCC-10), tillering(qTLCC-10) and heading stage(qHFLCC-10), respectively, was located in the same interval of XNpb333~R1629 on chromosome 10, suggesting that the expression of the locus is not susceptible to developmental time-space.2. Twenty-six QTLs for leaf chlorophyll degradation, by evaluating both chlorophyll degradation speed (CDS) and yellow leaf degree in rice, were mapped to most rice genomes except for chromosome 5, 7 and 10, which included sixteen and ten QTLs for CDS and YLD of detached/undetached leaf in rice, respectively, and accounted for 5.99%～27.79% of phenotypic variations.3. In comparison the genomic positions of those QTLs for undetached-leaf chlorophyll degradation with those QTLs for detached-leaf chlorophyll degradation at seedling stage, it was only found that the genomic region of qSLCDS-1 for undetached leaf CDS in interval of R3203-G2200 coincided with qSYDLD-1 for yellow detached leaf degree. However, most of others QTLs were located in different genomic regions, indicating that the genetic bases of detached and undetached leaf chlorophyll degradation are greatly different.4. After comparing those QTLs for leaf chlorophyll degradation at seedling, tillering and heading stage with those QTLs at maturity stage, non-QTLs were found to be located in the same region, which showing the genetic bases of leaf chlorophyll degradation at early stages(seedling and tillering stage) were obviously different from those at the maturity stage in rice. Thus, it may be unavailable for screening rice varieties with tolerance to leaf senescence at maturity through rapid determination of leaf senescence at early (seedling and tillering) stages in rice.5. In view of both three QTLs for leaf chlorophyll content and three QTLs for leaf chlorophyll degradation were located on the same genomic region between R3203~XNpb93 on chromosome 1, the region is importantly functional region for leaf chlorophyll content and chlorophyll degradation in rice.In this paper, a total of fifty-two QTLs for related leaf chlorophyll traits were detected at four different stages (seedling, tillering, heading and maturity stage) using the recombinant inbred (RI) population of Asominori/IR24. In addition, the results of this present study may be useful for marker-assisted selection for improvement of photosynthetic ability, fine mapping and cloning of those QTLs detected in rice.