QTL-seq analysis of powdery mildew resistance in a Korean cucumber inbred line
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ORIGINAL ARTICLE
QTL‑seq analysis of powdery mildew resistance in a Korean cucumber inbred line Chunying Zhang1,3 · Mahdi Badri Anarjan1 · Khin Thanda Win1 · Shahida Begum1 · Sanghyeob Lee1,2 Received: 16 June 2020 / Accepted: 8 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Key message QTL mapping and RT-PCR analyses identified the CsGy5G015660 as a strong powdery mildew resistance candidate gene and natural variation of CsGy5G015660 allele was observed using 115 core germplasm. Abstract Powdery mildew (PM) is among the most serious fungal diseases encountered in the cultivation of cucurbits. The development of PM-resistant inbred lines is thus of considerable significance for cucumber breeding programs. In this study, we applied bulked segregant analysis combined with QTL-seq to identify PM resistance loci using F 2 population derived from a cross between two Korean cucumber inbred lines, PM-R (resistant) and PM-S (susceptible). Genome-wide SNP profiling using bulks of the two extreme phenotypes identified two QTLs on chromosomes 5 and 6, designated pm5.2 and pm6.1, respectively. The two PM resistance loci were validated using molecular marker-based classical QTL analysis: pm5.2 (30% R2 at LOD 11) and pm6.1 (11% R2 at LOD 3.2). Furthermore, reverse transcriptase-PCR analyses, using genes found to be polymorphic between PM-R and PM-S, were conducted to identify the candidate gene(s) responsible for PM resistance. We found that transcripts of the gene CsGy5G015660, encoding a putative leucine-rich repeat receptor-like serine/ threonine-protein kinase (RPK2), showed specific accumulation in PM-R prior to the appearance of disease symptoms, and was accordingly considered a strong candidate gene for PM resistance. In addition, cleaved amplified polymorphic sequence markers from CsGy5G015660 were developed and used to screen 35 inbred lines. Natural variation in the CsGy5G015660 allele was also observed based on analysis of a core collection of 115 cucumber accessions. Our results provide new genetic insights for gaining a better understanding of the genetic basis of PM resistance in cucumber, and pave the way for further utilization in cucumber PM resistance breeding programs.
Introduction Communicated by Amnon Levi. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00122-020-03705-x) contains supplementary material, which is available to authorized users. * Sanghyeob Lee [email protected] 1
Plant Genomics Laboratory, Department of Bio‑Resource Engineering, College of Life Sciences, Sejong University, 209 Neungdong‑ro, Gwanjing‑gu, Seoul 05006, Republic of Korea
2
Plant Engineering Research Institute, Sejong University, 209 Neungdong‑ro, Gwanjing‑gu, Seoul 05006, Republic of Korea
3
Department of Integrated Bioindustry, Graduate School of Hanseo University, 46 hanseo 1‑ro, Haemi‑myun, Seosan‑si, Chungcheongnam‑do 31962, Republic of Korea
Cucumber (Cucumis sativus L.) is an economically important and widely cu
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