Page 5 - Molecular Plant Breeding

Molecular Plant Breeding 2010, Vol.1 No.3
http://mpb.sophiapublisher.com
Page 2 of 6
Genc and McDonald, 2004), salt tolerance (Gorham,
1990), cold tolerance (Limin and Fowler, 1993), water
logging tolerance (Villareal et al., 2001), pre-harvest
sprouting (Trethowan et al., 1998; Gatford et al.,
2002), increased level of iron concentration in grain
(Lage and Trethowan, 2008), end-use quality (William
et al., 1993; Peña et al., 1995), and yield components
(Villareal et al., 1994a; 1994b; Lage et al., 2006).
However, SHWs also carried a large number of
unfavorable traits, such as late maturity, tallness,
difficulty in threshing and red grain color. The last one,
red grain color, was an important factor limiting wheat
improvement. Over one thousand SHWs have been
produced from more than 600 Aegelops tauschii
accessions by the International Maize and Wheat
Improvement Center (CIMMYT) (Mujeeb et al., 1996;
Hajjar and Hodgkin, 2007; Maarten et al., 2007).
To enhance the genetic diversity of Chinese wheat
varieties, over two hundred synthetic hexaploid wheat
accessions from CIMMYT were introduced into China.
Elite synthetics were crossed and backcrossed with
Chinese commercial wheat cultivars to improve stripe
rust resistance, quality and yield potential. Advanced
lines with good resistance and high yield potential
were developed. In recent years, four synthetic
derivatives have been released in China. Among them,
Chuanmai 42, the first released CIMMYT synthetic
derivative in the world with beneficial traits as large
kernels, high spike weight, and resistance to new races
of local stripe rust, had the highest average yield
(>6t/ha) over two years in Sichuan provincial yield
trials, outyielding the commercial check cultivar
Chuanmai 107 by 20%~35% (Zhang et al., 2004;
Hajjar and Hodgkin, 2007; Maarten et al., 2007). Now,
Chuanmai 42 has become a popular wheat cultivar
throughout southwestern China and is playing a
significant role in wheat high yield breeding. However,
the character of red grain color is a limiting factor that
influences its distribution in some wheat region.
It was a cumbersome and time-intensive task to make
a conversion from red-seeded type to white-seeded
type, due to red grain color was dominant and three
homozygous recessive loci were needed for the
white-seeded type. Molecular markers have the
potential to facilitate the effectiveness of the recessive
allele selection for white variety breeding. Thus, for
this project, we mapped the gene(s) controlling the
character of red grain color in Chuanmai 42 derived
from SHW by SSR markers, and provided useful
markers for breeding white grain color variety by
using SHWs and Chuanmai 42 as genetic resources.
1 Results
1.1 Inheritance of red grain color in Chuanmai 42
The F1 seeds of all the other crossed combination with
Chuanmai 42 (red-grain color)×CW565 (white-grain
color) were uniformly of red-grain color as Chuanmai 42,
which confirmed that the red-grain color gene in
Chuanmai 42 was dominant gene to white. Phenotypic
analysis of F2 seeds found 774 red individuals and 241
white out of 1015 screened, which is not significantly
different from the 3:1 ratio (x2 =0.85, p>0.3) (Table 1),
indicating that the character of red grain color in
Chuanmai 42 was controlled by a single dominant gene.
1.2 Linkage analysis and R-D1 mapping
According to the pedigree of Chuanmai 42, it was
speculated that the red seed color alleles conferring
Chuanmai 42 are R-A1a, R-B1a and R-D1b. Therefore,
a total of 40 SSR markers on the chromosomes 3D
were used to screen the polymorphisms between the
two parents Chuanmai 42 and CW565. And eight SSR
markers were observed polymorphic on the long arm
of chromosome 3D.
Table 1 Segregation for red and white grain color in F2 progenies
Cross population No. of red grain
color plants
No. of white grain
color plants
No. of total plants X2
3:1 P-value No. of estimated
gene
Chuanmai42×CW565 774 241 1 015 0.85 0.25~0.75 1