The Genetic Bases Of Yield Relative Traits And Etiolation In Rice

It is generally considered that rice yield and its components (including tillers per plant, spikelets per panicle, seed setting ratio,1000-grain weight and yield per plant,) are inherited quantitatively and also affected by environment. In this study a recombinant inbred line (RILs) population between an indica variety, Teqing (TQ), and a wild compatible japonica variety,02428, was developed to identify quantitative trait loci (QTL) for yield and yield components traits in the three environments of two places and three years. The major QTLs with additive effects were analyzed by using QTL cartographer at the single-locus level, while the major QTLs, epistasis QTLs and interactions between QTLs and environments were analyzed by using QTLmapper at the two-locus level. According to the results of QTL analysis, two near isogenic lines of yield relative QTLs were developed to do fine mapping. The major results were as followed:1. A genetic map with 154 SSR markers was developed using RILs population. The map consisted of 13 linkage groups and had a total length of 1576 cM and an average distance of 10.3 cM between two adjacent markers.2. At single-locus level we scanned many QTLs:4 for heading date,4 for plant height, 6 for panicle length,5 for tillers per plant (TP),9 for spekilets per panicle (SPP),7 for kilo-grain weight (KGW), 4 for seed setting rate (SRT) and 2 for yield per plant (YD). At two-locus level, for TP, SPP, KGW, SRT and YD, we scanned 7,10,10,14 and 7 QTLs with additive effects,4,3,11,8 and 5 epistasis QTLs and 1,1,2,2 and 2 interaction between QTLs and environments, respectively. The results of QTL analysis confirmed that both of additive-effect QTLs and epistasis QTLs were the genetic bases of yield relative traits and that for different traits the two genetic effects played different parts. For example, the genetic bases of SPP was constituted with major QTLs with additive effects, while that of SRT was constituted with of the minor additive effects QTLs, most of which were also involved in interactions between two loci.3. Through prediction the KGW of RILs with extreme grain weight, it was sure that as well as the additive-effect QTLs, epistasis QTLs was also the genetic bases of transgressive segregation.4. Two QTLs, Gn4 for SPP and TP, and Gph3 for PH, PL and SPP, were analyzed in NIL populations. Gn4 and Gph3 were fine mapped into the region with a lenth of 183 kb and the interval between wph1 and RM16271, respectively. Additionally, a lethal mutant with etiolated seedlings derived form RI184, was found in RILs population. Using constructed F2 and F3 populations, it was confirmed that two recessive genes, named et11 and et12, controlled the etiolation phenotype. Et11 was fine mapped into the 147-kb interval in the distal part of chromosome 11, while Et12 was located into the 209-kb deleted region in the distal part of chromosome 12 in RI184. Both regions were within duplicated segments on chromosomes 11 and 12. They possessed a highly similar sequence of 38 kb at the locations of a pair of duplicated genes with protein sequences very similar to that of HCF152 in Arabidopsis that are required for the processing of chloroplast RNA. These genes are likely candidates for et11 and et12. Expression profiling was used to compare the expression patterns of paralogs in the duplicated segments. Expression profiling indicated that function buffering had taken effect in the duplicated segments, and a large number of the paralogs within the duplicated segments were functionally redundant like et11 and et12. Because there were one more copy of a fragment of chromosome 11 located onto unknown position and a 209-kb deletion on the chromosome 12, it was confirmed that a present crossover have taken place in RI184.