Fine-mapping Of QTL QPL-3 For Rice Panicle Length

Rice(Oryza sativa L.)is one of the most important food crops in the world.In recent years,the rice yield in China has been continuously improved.China is the most populous country in the world,with a huge demand for rice.With the increase of population and the decrease of arable land,it is imperative to further improve rice yield in order to meet the people’s demand for rice.The panicle length character of rice is one of the important yield components of rice and is closely related to rice yield.Therefore,identification and fine-mapping of QTL controlling panicle length of rice can further deepen the understanding of its genetic mechanism and provide more reliable theoretical support for breeding work.In this study,there is a QTL controlling the panicle length of rice,which is named qPL-3 by using a set of chromosome segment substitution line population derived from indica/japonica cross(Sasanishiki/Habataki).We further found that CSSL SL411 contained this locus and the panicle length was obviously shorter than those of its background parent Sasanishiki.Thus SL411 was selected to cross with Sasanishiki to construct advanced population for genetic analysis and gene mapping for the QTL qPL-3 of rice panicle length.The main results are as follows:1.According to the investigation of the panicle length of the parents in two places and three years of SL411 and Sasanishiki in recent years,the panicle length of SL411 is significantly shorter than that of background parent Sasanishiki,and genotyping showed that SL411 only contains Habataki introduced fragment on the end of chromosome 3,and other fragments are completely consistent with background parent Sasanishiki.The above results showed that the shorten panicle length of SL411 was caused by Habataki introgression fragment.2.In order to finely map qPL-3,F2 population was obtained by backcrossing SL411 with Sasanishiki followed self-crossing,and the panicle length of population was investigated.QTL mapping was carried out in combination with genotypes of population.qPL-3 was initially mapped between marker 3-64 and 3-323,the physical distance is about 1900kb.3.In order to further narrow the qPL-3 target interval,plants with heterozygous genotypes in the target region were selected in the F2 population to form the F3 and F4 population.Polymorphic markers are further developed between 3-64 and 3-323 for genotyping,and the individuals with homozygous genotypes covering the qPL-3 located region were selected.Finally,we obtained 9 different homozygous genotypes formed a set of contigs,named R1-R9,covering the target region.The panicle lengths of these 9 overlapping types were investigated,and it was found that the panicle length of R5,R6,R7,R8 and R9 was significantly longer than that of R1,R2,R3 and R4.Thus,combined with multiple comparative analysis of genotypes,we positioned qPL-3 in a 216.6kb-long region governed by marker P-304 and L31.Gene prediction shows that there are 36 candidate genes in this region.4.To further clarify the genetic effects of qPL-3,R4 and R5 were selected to study their agronomic characters of panicle,the results clearly showed that the number of grains per panicle,number of primary branch and panicle length differed significantly between R4 and R5,however,there were no significant differences in grain length,grain width and 1000-grain weight,indicating that qPL-3 could change the panicle length at the same time also affect the number of grains per panicle and number of primary branch.