Mapping of QTLs Controlling Grain Shape and Populations Construction Derived from Related Residual Heterozygous Lines in Rice

Xiaowu Pan,Tingting Lu,Xiaoxiang Li,Kun Zhou,Yongchao Li,Wenqiang Liu,Xinnian Sheng

doi:10.5539/jas.v8n9p104

Abstract

Grain shape is usually characterized by grain length (GL), grain width (GW), grain thickness (GT) and length to width ratio (LWR), and controlled by quantitative trait locus (QTL). In this paper, QTL analysis was performed using an F2 population and an F8 recombinant inbred line (RIL) population from a cross Xiang743/Katy. A total of 38 QTLs for grain shape were detected and eight of them were repeatedly identified in both populations. Seven for GL, five for GW, five for GT, and eight for LWR were detected in F2 population, explaining totally phenotypic variance of 94.51%, 61.52%, 54.33% and 91.84%, respectively. Five for GL, three for GW, and five for LWR were detected in RILpopulation, explaining totally phenotypic variance of 39.83%, 37.52% and 36.71%, respectively. Many QTLs were located in similar intervals, contributing to complicated trait correlation. A few QTLs were mapped in intervals coincided with previously cloned genes associated with grain size. Two residual heterozygous lines (RHLs) were selected out on the basis of newly identified loci, populations derived from RHLs were constructed for fine mapping QTLs associated with grain shape.

Highlights

Grain shape, closely correlated with grain weight, a major component of grain yield in rice (Lin and Wu. 2002), is usually characterized by grain length (GL), grain width (GW), grain thickness (GT) and length to width ratio (LWR) (GL was divided by GW with a grain)
The results showed that these distributions in F2 population were highly similar with those in recombinant inbred line (RIL) population
Two populations from a cross Xiang743/Katy were used for mapping quantitative trait locus (QTL) underlying GL, GW, GT and LWR

Summary

Introduction

Closely correlated with grain weight, a major component of grain yield in rice (Lin and Wu. 2002), is usually characterized by GL (the maximum distance of a grain from top to bottom), GW (the most widest distance between two sides within a grain), GT (the most thickest distance within a grain) and LWR (GL was divided by GW with a grain). Two major QTLs for GL and grain weight were repeatedly identified on chromosome three and seven respectively in many independent studies (Bai et al, 2010; Li et al, 2004; Qiu et al, 2012; Shao et al, 2010; Shao et al, 2012; Thomson et al, 2003; Xiao et al, 1998). These QTLs could be utilized for improving grain shape in rice breeding program, but with consideration of pleiotropism

Methods

Results

Conclusion