Functional analysis of starch-synthesis genes in determining rice eating and cooking qualities
2006
He, Ying | Han, Yuepeng | Jiang, Lu | Xu, Chenwu | Lu, Jufei | Xu, Mingliang
Apparent amylose content (AAC), gel consistency (GC), and gelatinization temperature (GT) are recognized as the most important determinants of rice eating and cooking qualities. The contributions of major starch-synthesis genes to these three traits have been investigated in the three consecutive experiments. In an initial QTL mapping with 130 doubled haploid (DH) lines, derived from an inter-subspecific cross of 'Nanjing11'/'Balilla', the major QTLs responsible for AAC, GC, and GT coincided with the Wx (granule-bound starch synthase gene), Wx, and Sss IIa (soluble starch synthase gene) loci, respectively. In the second experiment, contributions of the major starch-synthesis genes to AAC, GC, and GT variations were estimated by using a multiple linear regression analysis. As shown, the Wx locus was a principal determinant for both AAC and GC, and could account for 58.5% and 38.9% of the phenotypic variations, respectively; while the Sss IIa locus was associated with GT, and could explain 25.5% of the observed variation. Eventually, a F₂ population consisting of 501 individuals, derived from an inter-subspecific cross of the two sticky rice varieties 'Suyunuo' and 'Yangfunuo 4', was examined with gene-tagged markers. In the absence of the Wx gene, none of the starch-synthesis genes investigated could dominate the GC variation, however, the Sss IIa locus could also explain 25.1% of the GT variation. In summary, the Wx locus dominates the AAC variation, and meanwhile plays a major role in the GC variation. The Sss IIa locus is a major factor in explaining the GT variation. Apart from the major genes, other genetic factors may also contribute to the GC/GT variations.
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