Abstract
BackgroundAmylose content (AC) is a critical factor for the quality of rice. It is determined by the biosynthesis gene Waxy (Wx) and a variety of quantitative trait loci (QTLs). Although many QTLs have been reported to affect rice AC, few of them have been investigated under varying growth conditions, especially various temperatures, which are known to greatly influence the AC.ResultsWe analyzed the AC at different temperatures and planting seasons in a set of chromosome segment substitution lines (CSSLs) which were derived from a cross between the indica variety 9311 and the japonica variety Nipponbare carrying the same Wxb allele. A joint analysis detected a single locus, qSAC3, with a high logarithm of odds (LOD) score in four different conditions. The qSAC3 from indica 9311 (qSAC3ind) substantially increased the AC in japonica Nipponbare under all tested growth conditions. Furthermore, introducing the qSAC3ind into the soft rice variety Nangeng9108 with Wxmq, a mutant allele of Wxb, also moderately increased its AC and improved its appearance quality significantly by reducing the chalkiness of the polished rice.ConclusionsOur results indicate that the qSAC3ind could increase the AC of japonica rice in different environments as well as in the background of different Wx alleles and that qSAC3 is a valuable locus for fine-tuning the rice AC and ameliorating the dull endosperm in rice varieties with the Wxmq allele.
Highlights
Amylose content (AC) is a critical factor for the quality of rice
AC of chromosome segment substitution lines (CSSLs) and NIP vary under different environments A set of CSSLs was used in this study
Rice seeds sown in June and in July and plants grown in the field were set as normal season (NS) and late season (LS) treatments, respectively, while the plants transferred to growth chambers with different temperatures after flowering were set as high temperature (HT, 35 °C/28 °C) and room temperature (RT, 28 °C/22 °C) treatments
Summary
Amylose content (AC) is a critical factor for the quality of rice. It is determined by the biosynthesis gene Waxy (Wx) and a variety of quantitative trait loci (QTLs). The major locus, Wx, is located on chromosome 6 [4,5,6,7]. Two major Wx alleles, Wxa and Wxb, occur widely in Asian cultivated rice (Oryza sativa L). Wxa is mainly distributed in indica, a subspecies with high AC (> 20%), whereas Wxb is widely found in japonica, a subspecies with low to intermediate AC (< 20%) [8, 11, 12]. Two single nucleotide substitutions that cause missense base changes occurred in the Wxmq coding region compared to the wild type allele (Wxb). Low AC (~ 10%) and high chalkiness in rice seed with Wxmq may be due to the impaired enzyme activity of the GBSSI protein [17]
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