Fine Mapping Of A Heading Date QTL QHd5.1 In Rice

Rice is one of the most important crops in the world,providing the stable food for nearly half of the world’s population.Suitable heading date plays an important role in ensuring stable and high yield of rice.It is of great significance for breeding and variety extension to discover and identify rice heading date genes and perfect rice heading date gene regulatory network.This study was based on a set of 175 chromosome segment substitution lines with Guangluai 4 as the recipient parent and Nipponbare as the donor parent,which covered 12 chromosomes of rice.The heading date of substitution line C32052 was 22 days longer than that of its receptor parent Guangluai 4,and the difference of grain width was also significant.The heading date of F2 segregation population backcross between Substitution Line C32052 and Guangluai 4 was 1:3(χ2=0.107<χ20.05=3.84),48 plants heading early,and 152 plants heading late.141 plants whose grain width was less than 3.45 mm and 59 plants whose grain width was more than 3.45 mm were isolated from the population with a Gregor Mendel ratio of 3:1(χ2=2.16<χ20.05=3.84).The qHd5.1 locus was initially located within the 0.64 Mb interval between InD5-2 and InD5-12 by using the recessive single plant in the segregation population of 200 individuals.The results showed that the qHd5.1 locus was located within the 0.64 Mb interval between InD5-2 and InD5-12 in chromosome 5.F3 generation was obtained by screening F2 population from InD5-2 and InD5-12.A total of 30 lines were used to expand the population for fine mapping.A more intensive InDel markers were developed to detect 1051 recessive individuals,and finally,qHd5.1 was located in the 18 Kb interval between C5-5 and W5-18.There are two functional annotation genes in this 18 Kb candidate region,LOC_Os05g14270 and LOC_Os05g14280.The expression of LOC_Os05g14270 in C32052 was significantly lower than that in Guangluai4,and LOC_Os05g14280 in C32052 was significantly higher than that in Guangluai4.Sequence analysis showed that there were mutations in LOC_Os05g14270 coding sequence between C32052 and Guangluai 4,which resulted in differences in amino acid sequences.Therefore,this study suggests that LOC_Os05g14270 is the candidate gene.The results lay a foundation for cloning of qHd5.1.