Quantitative trait locus (QTL) analysis is a powerful approach for identifying variants associated with the phenotypic variation of complex traits. However, selecting optimal methods and pre-processing steps require considerable time and effort. In this study, we demonstrated applicability and replicability of machine learning (ML) models in QTL analysis by evaluating their performance in comparison with conventional QTL analysis methods using 142 recombinant inbred lines derived from two
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The yield related traits are controlled by multiple quantitative trait loci (QTLs) and influenced by environmental change in rice. We analyzed QTLs for 15 yield related traits using two backcross populations, derived from crosses between IR64 as recurrent parent and Koshihikari as donor parent, through two years. A total of 67 backcross inbred lines (BILs) and 40 chromosome segment substitution lines (CSSLs) were genotyped using 183 SNP markers using a high-throughput genotyping system. Some genomic gaps between markers were identified in two populations. For fifteen traits in this study, 36 major QTLs (mQTLs) for 12 traits and 16 digenic epistatic QTLs (EpQTLs) for culm length were detected in BILs. On the other hand, 17 mQTLs were detected for nine traits in CSSLs. Among them, six mQTLs for grain yield traits were collocated on chromosome 10 in both years. For spikelet fertility, six putative QTLs were detected under high temperature conditions in 2018. The QTLs identified in this study could be used for the development of rice varieties conferring inter-subspecific combinations of yield-related traits.
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Seedling vigor in drought stress conditions is an important characteristic of the dry direct-seeded rice system. The drought stress in the seedling stage disrupts seed germination and delays the establishment of seedlings. However, little is known about the genetic mechanism of seedling vigor in drought conditions. The identification of quantitative trait loci (QTL) was conducted using 162 recombinant inbred lines (RILs) derived from a cross between two rice varieties—a Tongil-type Milyang23 and a temperate japonica Tong88-7. The seedling vigor of these RILs was characterized by measuring 10 morphological traits of the seedlings grown under drought conditions. The Tong88-7 seedlings showed significantly higher values than the Milyang23 seedlings for all traits. The genotyping-by-sequencing method was used to construct a map of 6140 single nucleotide polymorphisms. Six main-effect QTLs (M-QTLs) associated with seedling vigor traits under drought stress were identified on chromosomes 9 and 11. In particular, five out of these six QTLs were located on chromosome 11, explaining the phenotypic variances of 4.3% through 10.1%. In addition, 21 epistatic QTLs (E-QTLs) were detected, and the 27 loci involved in this interaction were distributed on 11 chromosomes. Both M-QTLs and E-QTLs detected in this study would be useful in breeding programs to develop elite rice varieties especially adapted to dry direct-seeded rice system.
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