Mapping Of Qtls For Pre-harvest Sprouting And Heading Date In Rice(Oryza Sativa L.)

Rice is a stable food.However,pre-harvest sprouting(PHS)often occurs in the southern rice region of China,due to continuous rain in the mature period.PHS not only causes yield reduction but also affects grain quality and seed quality seriously.Therefore,it is of great significance to mine the genes associated with PHS and breed rice varieties resistant to PHS.Here,we used B1923,a easy-sprouting in pre-harvest japonica line,and 93-11 to construct an F2 population for QTL analysis.Based on the results of QTL mapping,F2:3 self-segregating line and BC1F2 population were developed,to verify the QTL.The results were as follows:The germination rate of each F2 plant was evaluated at 35 days after its heading.The genetic linkage map was constructed to detect QTL for PHS.A total of 9 PHS QTL were mapped on chromosomel(qPHS-1)chromosome2(qPHS-2-1 and qPHS-2-2),chromosome 3(qPHS-3-1 and qPHS-3-2),chromosome4(qPHS-4),chromosome7(qPHS-7),chromosome 11(qPHS-11)and chromosome 12(qPHS-12)respectively.The major QTL qPHS-12 is located between markers of K44～W82,explaining 24.97%of the phenotype variation,with a LOD of 20.68,and the genotype of high germination rate from B1923.For other QTL,the phenotype contributions was only ranged from 4.28%to 7.76%.For the major QTL qPHS12,a BC1F2 population was developed by molecular marker selection.QTL analysis showed that two QTL were detected on chromosome 12.qPHS-12-1 was located on the interval of the markers K39 and Y88,explaining 4.17%of phenotypic variation,with a LOD score of 2.03.The qPHS-12-2 was mapped between the markers K44 and K187,explaining 9.60%of penotypic varition,with a LOD of 25.52.This locus is in the same interval as the qPHS-12 detected in F2 population,suggesting that qPHS-12 can be repeated between two generations in different years and could be inherited stably.For the QTL detected on the 1,2,7 chromosomes,F2:3 lines developed from F2 plants by marker assisted selection.QTL verification show that only the qPHS-2-2 was detected again between markers of W29～A96,explaining 10.55%of phenotypic varition,with a LOD score of 3.48.Due to the influence of genetic background or environmental conditions in different years,other minor QTL couldn’t be found in F3 lines.The heading date(HD)is an important agronomic trait of rice and that determines adaptability to specific natural environments,such as season and region.HD also has effect on rice yield.In this study,we use two varieties with obvious differences in heading date as parents:Ninggeng NO.1 and YR1.A BC2F3 population,segregating in HD,was obtained by backcrossing with Ninggeng NO.1.Molecular genetic map was constructed to mapping QTL for heading date.Two QTL,qHD3 and qHD10 were found.qHD3 was mapped between the marker RM8267～RM8277 on chromosome 3.Its LOD score is 5.75,explaining 0.93%of phenotypic variation.qHD10-1 was located between the marker RM258-S73 on chromosome 10.Its LOD score is 8.02,explaining 7.25%of phenotypic variation.