Association of SNPs [single nucleotide polymorphisms] on waxy gene with gel consistency and the proportion of soluble and insoluble amylose chains in rice grains
2010
Tran Anh Nguyet, Philippines Univ. Los Baños, College, Laguna (Philippines)
Gel consistency (GC) is a standard assay used to classify the processing and cooking quality of high amylose content rice cultivars. The Waxy (Wx) gene on rice chromosome 6 codes for granule-bound starch synthase I (GBSSI) which is responsible for amylose content, which defines many parameters of grain texture. The association between a single nucleotide polymorphism (SNP) in the Wx gene and gel consistency (GC) was determined using recombinant inbred lines of the parentals IR8 and IR5. A SNP in the exon 10 of waxy gene associated perfectly with high and low GC. This association was validated using a diverse set of rice varieties. An allele specific oligonucleotide primers based on the SNP that allow the direct detection of gel consistency was developed. This can be used in marker aided selection of excellent cooking properties in breeding populations. This SNP is an important additional marker in the palette of markers for grain quality. Factors leading to differences in GC and the relationship of the proportion of amylose that leached from the grain with GC were identified. It was shown that rice genotypes with firm GC do not change in texture over 24 h, whereas rice genotypes with soft GC reach the same firmness more slowly than those with hard GC. The mutation on exon 10 of the Waxy gene somehow affects the proportion of amylose bound to amylopectin and the proportion of amylose that are able to leach from the starch granules. These structural differences affect the amount of time and gel takes to reach a final hardness.
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