Cold stress is one of the serious abiotic stresses for stable rice production especially in high-latitude temperate region and high-altitude tropical area. Improving cold tolerance at seedling stage led stable seedling growth with yield stability. In this study, QTLs for cold tolerance at seedling stage were identified using the 96 introgression lines (ILs) derived from an inter-specific cross between Hwaseong (
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The
objective
of this study was to detect QTLs for rice seedling traits under normal water (control) and low water conditions (drought stress). Ninety-eight recombinant inbred lines (RILs) from a cross between closely-related japonica cultivars, M-203 and M-206 were grown under both low water and normal water conditions. QTLs for morphological traits were investigated at seedling stage using 5,164 single nucleotide polymorphisms via genotyping-by-sequencing. Twenty-three QTLs were associated with four seedling traits: shoot length (SL), root length (RL), shoot dry weight (SW) and root dry weight (RW), were detected and most QTLs were clustered on chromosome 1, 6, 7 and 11. Under normal water conditions, nine QTLs for seedling traits were detected and M-203 alleles increased all the values. The locations of most QTLs were consistent with genes that regulate or respond to auxin and gibberellin. For drought tolerance, fourteen QTLs were detected including seven for drought stress conditions and seven for relative performance (values from drought stress conditions/normal water conditions). Seven QTLs from drought stress conditions coincided with the loci of previously identified drought tolerance genes. Based on the shoot and root length under drought stress conditions, five lines exhibiting the highest values in common were selected as a drought tolerance group. Those lines exhibited better growth than the parents under drought stress conditions and had QTLs alleles for drought tolerance detected in this study. QTL information and selected lines may be used for improving seedling vigor and drought tolerance of rice in breeding programs.
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Studies were initiated for two consecutive years to examine the effects of transplanting date on the yield and quality of early maturing rice cultivars and to select rice cultivars capable of adapting to early transplanting in the middle plain area. The experiment was laid out in a split-plot design with 3 replications. The main plots consisted of two transplanting dates viz. early (25th of April) and ordinary (25th of May), with sub-plots containing eight cultivars. For early transplanting the mean temperature at the grain filling stage was lower than for ordinary transplanting, while the rice grain quality traits and palatability values were improved. Early transplanting results in 11 days earlier heading, higher head rice yield and lower milled rice yield than ordinary transplanting. Significant differences among the eight cultivars tested in this study were observed for most traits. Among cultivars, ‘Joami’ demonstrated the highest palatability. ‘Joami’ also performed better in head rice ratio and head rice yield than ‘Unkwang’, which is widely cultivated in the middle plain area. Palatability value (PV) showed significant positive correlations with head rice ratio (HR) and amylose content (AC), and negative correlations with chalky rice ratio (CR) and protein content (PC). Mean temperature (MT) was positively correlated with CR and PC, and negatively correlated with HR and AC. The highest positive and negative correlations among the rice quality traits were observed between HR and AC (r = 0.734), and HR and CR (r = −0.944), respectively. Based on the research findings, ‘Joami’ is suitable for early transplanting for cultivation in the Chungnam plain area.
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Although traditional rice varieties and wild rice species exhibit vast genetic diversity, the transfer of useful genes to modern varieties is often hampered by linkage drag. In this study, the previously identified blast resistance locus
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