Abstract
Previously, five putative quantitative trait loci (QTLs) for low-temperature germination (LTG) have been detected using 96 BC3F8 lines derived from an interspecific cross between the Korean japonica cultivar “Hwaseong” and Oryza rufipogon. In the present study, two introgression lines, CR1517 and CR1518, were used as parents to detect additional QTLs and analyze interactions among QTLs for LTG. The F2 population (154 plants) along with parental lines, Hwaseong and O. rufipogon, were evaluated for LTG and coleoptile length under low-temperature conditions (13 °C). Among five QTLs for LTG, two major QTLs, qLTG1 and qLTG3, were consistently detected at 6 and 7 days after incubation. Three minor QTLs were detected on chromosomes 8 and 10. Two QTLs, qLTG10.1 and qLTG10.2, showing linkage on chromosome 10, exerted opposite effects with the Hwaseong allele at qLTG10.2 and the O. rufipogon allele at qLTG10.1 respectively, in turn, increasing LTG. Interactions among QTLs were not significant, implying that the QTLs act in an additive manner. Near-isogenic line plants with the combination of favorable alleles from O. rufipogon and Hwaseong exhibited higher LTG than two introgression lines. With regard to coleoptile length, three QTLs observed on chromosomes 1, 3, and 8 were colocalized with QTLs for LTG, suggesting the pleiotropy of the single gene at each locus. According to the results, the introgression of favorable O. rufipogon alleles could hasten the development of rice with high LTG and high coleoptile elongation in japonica cultivars.
Highlights
Rice is one of the most important crops, feeding more than a third of the global population.Global rice demand is projected to rise from 723 million tons in 2015 to 763 million tons by 2020 and is expected to increase further to 852 million tons by 2035 [1]
The seeds of O. rufipogon began germinating at 1 days after incubation (DAI), with a 47% germination rate
There were no significant differences in germination rate among the parental lines from 3 to 4 DAI under the control temperature (Figure S2)
Summary
Rice is one of the most important crops, feeding more than a third of the global population. Global rice demand is projected to rise from 723 million tons in 2015 to 763 million tons by 2020 and is expected to increase further to 852 million tons by 2035 [1]. To feed the growing population, rice production needs to be improved and stabilized, globally and regionally. Improving potential yield and incorporation of biotic and abiotic stress tolerance mechanisms would facilitate the achievement of such goals. Wild relatives of rice are rich sources of desirable genes, with regard to yield and with regard to disease resistance, stress tolerance, and other traits [2,3]. Exploring wild and exotic rice germplasm for desirable genes and transferring them into cultivars through crossing and
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