Abstract
The rates of grain-setting in apical and basal spikelets in wheat directly affect the kernel number per spike (KNPS). In this study, 220 wheat lines from 18 Chinese provinces and five foreign countries were used as a natural population. Phenotypic analysis showed differences in grain-setting rates between apical and basal spikelets. The broad-sense heritability of grain-setting rate in apical spikelets (18.7–21.0%) was higher than that for basal spikelets (9.4–16.4%). Significant correlations were found between KNPS and grain numbers in apical (R2 = 0.40–0.45, P < 0.01) and basal (R2 = 0.41–0.56, P < 0.01) spikelets. Seventy two of 106 SSR markers were associated with grain setting, 32 for apical spikelets, and 34 for basal spikelets. The SSR loci were located on 17 chromosomes, except 3A, 3D, 4A, and 7D, and explained 3.7–22.9% of the phenotypic variance. Four markers, Xcfa2153-1A202, Xgwm186-5A118, Xgwm156-3B319, and Xgwm537-7B210, showed the largest effects on grain numbers in apical and basal spikelets. High grain numbers in apical and basal spikelets were associated with elite alleles. Ningmai 9, Ning 0569, and Yangmai 18 with high grain-setting rates carried larger numbers of favorable alleles. Comparison of grain numbers in basal and apical spikelets of 35 Yangmai and Ningmai lines indicated that the Ningmai lines had better grain-setting rates (mean 21.4) than the Yangmai lines (16.5).
Highlights
Wheat is one of the most important cereal crops in the world
Similar numbers of grains were produced in all apical spikelets
Grain yield of wheat will be enhanced if the kernel number per spike (KNPS) is increased by 1 or 2 while other yield factors remain constant (Arisnabarreta and Miralles, 2006; Acreche et al, 2008)
Summary
Wheat is one of the most important cereal crops in the world. As the third-largest crop in China, the average grain yield of wheat has reached 4986 kg/ha, and the maximum was more than 12,000 kg/ha (National Bureau of Statistics of China, http://data.stats.gov.cn). Improved grain yield is still the most important objective in wheat breeding. GNAS and GNBS in Wheat spike (KNPS) and thousand grain weight (TGW) are important grain yield components. At a fixed spike number per square meter and fixed TGW, improvements in grain yield will depend largely on increasing KNPS (Slafer and Andrade, 1989; Fischer, 1993, 2008, 2011; Magrin et al, 1993). The numbers of grain produced in apical and basal spikelets become key factors for achieving high kernel numbers per spike (Arisnabarreta and Miralles, 2006; Acreche et al, 2008)
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