Fine Mapping of QTLs for Stigma Exsertion Rate from Oryza glaberrima by Chromosome Segment Substitution

Common wild rice contains valuable resources of novel alleles for rice improvement. It is well known that genetic populations provide the basis for a wide range of genetic and genomic studies. In particular, chromosome segment substitution lines (CSSLs) ais a powerful tool for fine mapping of quantitative traits, new gene discovery and marker-assisted breeding. In this study, 132 CSSLs were developed from a cultivated rice (Oryza sativa) cultivar (93-11) and common wild rice (Oryza rufipogon Griff. DP30) by selfing-crossing, backcrossing and marker-assisted selection (MAS). Based on the high-throughput sequencing of the 93-11 and DP30, 285 pairs of Insertion-deletions (InDel) markers were selected with an average distance of 1.23 Mb. The length of this DP30-CSSLs library was 536.4 cM. The coverage rate of substitution lines cumulatively overlapping the whole genome of DP30 was about 91.55%. DP30-CSSLs were used to analyze the variation for 17 traits leading to the detection of 36 quantitative trait loci (QTLs) with significant phenotypic effects. A cold-tolerant line (RZ) was selected to construct a secondary mapping F2 population, which revealed that qCT2.1 is in the 1.7 Mb region of chromosome 2. These CSSLs may, therefore, provide powerful tools for genome wide large-scale gene discovery in wild rice. This research will also facilitate fine mapping and cloning of QTLs and genome-wide study of wild rice. Moreover, these CSSLs will provide a foundation for rice variety improvement.

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Identification and Fine-Mapping of a Novel QTL qMrdd2 Conferring Resistance to Maize Rough Dwarf Disease

Plant Disease ◽

10.1094/pdis-03-20-0495-re ◽

2021 ◽

Author(s):

Zhennan Xu ◽

Feifei Wang ◽

Zhiqiang Zhou ◽

Qingchang Meng ◽

Yanping Chen ◽

...

Keyword(s):

Fine Mapping ◽

Recombinant Inbred ◽

Recombinant Inbred Lines ◽

Substitution Line ◽

Chromosome Segment ◽

Phenotypic Variance ◽

Chromosome Segment Substitution Line ◽

Maize Rough Dwarf Disease ◽

Dwarf Disease ◽

Segment Substitution

Maize rough dwarf disease (MRDD), caused by a virus, seriously affects maize quality and yield worldwide. MRDD can be most effectively controlled with disease-resistant hybrids of corn. Here, MRDD-resistant (Qi319) and -susceptible (Ye478) parental inbred maize lines and their 314 recombinant inbred lines (RILs) that were derived from a cross between them were evaluated across three environments. A stable resistance QTL, qMrdd2, was identified and mapped using BLUP values to a 0.55 Mb region between the markers MK807 and MK811 on chromosome 2 (B73 RefGen_v3), which was found to explain 8.6 to 11.0% of the total phenotypic variance in MRDD resistance. We validated the effect of qMrdd2 using a chromosome segment substitution line (CSSL) that was derived from a cross between maize inbred Qi319 as the MRDD resistance donor and Ye478 as the recipient. Disease severity index of the CSSL haplotype II harboring qMrdd2 was significantly lower than that of the susceptible parent Ye478. Subsequently, we fine-mapped qMrdd2 to a 315 kb region flanked by the markers RD81 and RD87 by testing recombinant-derived progeny using selfed backcrossed families. In this study, we identified a novel QTL for MRDD-resistance by combining the RIL and CSSL populations, which can be used to breed for MRDD resistant varieties of maize. Keywords: Maize, Maize rough dwarf disease, QTL, Fine-mapping, Recombinant inbred line, Chromosome segment substitution line.

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