Pyramiding seed dormancy genes to improve resistance of semi-dwarf varieties to pre-harvest sprouting in rice
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Pyramiding seed dormancy genes to improve resistance of semi-dwarf varieties to pre-harvest sprouting in rice Junwei Wang & Ugur Korkmaz & Min Guo & Wirat Pipatpongpinyo & Xing-You Gu
Received: 15 June 2020 / Accepted: 8 September 2020 # Springer Nature B.V. 2020
Abstract The quantitative trait locus SD1-2 for seed dormancy (SD) is identical to the semi-dawrf1 (sd1) gene prevailing in high-yield varieties of rice. However, sd1 alone appeared not sufficient to overcome the preharvest sprouting (PHS) problem in crop (or hybrid seed) production. This research aimed to address some genetic issues that may impact pyramiding of SD genes to improve semi-dwarf varieties for the PHS resistance. The isolated SD1-2, SD8, and SD10 loci were also associated with plant height (PH), awn or flowering time (FT), with the dormancy-enhancing alleles reducing stem elongation, increasing awned seeds, and promoting flowering, respectively. Allelic variants at SD1-2 and SD8 or SD10 were assembled in the same background as two digenic systems, each consisting of all the nine digenic genotypes. The two systems of plants were evaluated for the four traits and phenotypic data used to model trait correlations and the component additive, dominance, and epistatic effects of the two loci. FT was correlated with PH and germinability, but the J. Wang : U. Korkmaz : M. Guo : W. Pipatpongpinyo : X. 3 mm) seeds were counted at the 7th day to calculate the germination percentage for a sample. Means of the three replicates from a plant were used for genetic analysis. Only partially awned plants were observed in the SD1-2-SD8 system (experiment 1), and the awn length was short than 2 cm. Thus, the trait awn was quantified by the percentage of awned seeds in a sample of 200 seeds from a plant. Quantitative genetic analysis Linear correlation analysis was used to estimate the strength and direction of associations between traits evaluated for each of the two digenic systems. Genotypic variation for each of the traits in a digenic system was partitioned into component effects of the two loci using the linear repression model: yl ¼ μ þ a1 xi þ d 1 zi þ a2 x j þ d 2 z j þ I a1a2 wij þ I a1d2 wij þ I d1a2 wij þ I d1d2 wij þ εl
ð1Þ
where yl is the phenotypic value for plant l (l = 1 to N, the sample size for a population); μ is the intercept or mean of the model; xi and xj are dummy variables for the first (SD1-2) and second (SD8 or SD10) loci, respectively, with i or j = − 1, 0, and 1 for genotypes homozygous for the allele from the parent EM93-1, heterozygous, and homozygous for the allele from the parent SS18-2, respectively; a1 and a2 are partial regression coefficients of the variables and estimates of additive effects for the loci i and j, respectively; zi and zj are dummy variables for the two loci, but i or j = − 0.5 for the homozygotes or 0.5 for the heterozygote; d1 and d2 are partial regression coefficients of the variables and estimates of dominance effects for loci i and j, respectively; “wij”s are dummy variables for epistatic interactions, w
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