Molecular Plant Breeding 2016, Vol.7, No.12, 1
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Figure 3 Genome-wide scanning of grain size related QTLs for (A) grain length, (B) grain width, (C) length to width ratio, (D) 1
000-grain weight in F
2
population using QTL IciMapping 4.0
1.5 Digenic epistasis analysis
The total of 37 locus pairs showed significant epistatic effect on all the grain size related traits in this study (Suppl
Table 2). These loci were distributed on all the rice chromosomes. The contribution of epistatic effect of detected
locus pairs to phenotypic variation ranged from 12.42 to 64.09%. Among them, 24 pairs had a higher effect than
that of
qGL-3
, a QTL with the highest phenotypic contribution in this study (Table 4; Supplement Table 2). These
indicated that the effect of digenic interaction also plays a key role in the variation of grain size related phenotypes,
and accounts for a large proportion of genetic variation. Among the identified QTLs, five were involved in digenic
epistasis, therein, three for GL (
qGL-1, qGL-3, qGL-4
), one for LWR (
qLWR-12
), and one for TGW (
qTGW-5
),
respectively.
qLWR-12
involved in five-pair digenic interactions (Supplement Table 2), indicating that
qLWR-12
also involves in controlling GL and GW through digenic interactions.
2 Discussion
Rice grain weight, one of the key determinants for rice grain yield, is determined by grain length, width, thickness,
and length to width ratio, which is referred to as grain size related traits. Grain size related traits have been
received attention increasingly since 1990s. A great number of QTLs have been identified for rice grain size and
shape by using different mapping populations (Bai et al., 2010, 2012; Huang et al., 2013; Lou et al., 2009).
However, most mapping populations used in those studies derived from crossing between medium grain size
parents (Bai et al., 2010). In this study, a large grain size parent, NYZ, and a relatively small grain size parent,
Ce253, were used to generate mapping population for grain size QTL analysis. A total of 15 QTLs were identified
for rice GL, GW, LWR, TGW except GT (Figure 4; Table 4). Among these, two QTLs
qGL-4
and
qGL-9
, with
minor effect for grain length, were reported for the first time here.
