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Theor Appl Genet. 2018 Jul;131(7):1577-1587. doi: 10.1007/s00122-018-3099-1. Epub 2018 Apr 21.

STAYGREEN (CsSGR) is a candidate for the anthracnose (Colletotrichum orbiculare) resistance locus cla in Gy14 cucumber.

Pan J1,2, Tan J1, Wang Y1, Zheng X3,4, Owens K3,4, Li D1,5, Li Y1,5, Weng Y6,7.

Author information

1
Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.
2
Department of Plant Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China.
3
Magnum Seeds Inc., Dixon, CA, 95620, USA.
4
HM Clause Seed Company, Dixon, CA, 95260, USA.
5
Horticulture College, Northwest A&F University, Yangling, 712100, China.
6
Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA. yiqun.weng@ars.usda.gov.
7
Vegetable Crops Research Unit, USDA-ARS, 1575 Linden Drive, Madison, WI, 53706, USA. yiqun.weng@ars.usda.gov.

Abstract

Map-based cloning identified a candidate gene for resistance to the anthracnose fungal pathogen Colletotrichum orbiculare in cucumber, which reveals a novel function for the highly conserved STAYGREEN family genes for host disease resistance in plants. Colletotrichum orbiculare is a hemibiotrophic fungal pathogen that causes anthracnose disease in cucumber and other cucurbit crops. No host resistance genes against the anthracnose pathogens have been cloned in crop plants. Here, we reported fine mapping and cloning of a resistance gene to the race 1 anthracnose pathogen in cucumber inbred lines Gy14 and WI 2757. Phenotypic and QTL analysis in multiple populations revealed that a single recessive gene, cla, was underlying anthracnose resistance in both lines, but WI2757 carried an additional minor-effect QTL. Fine mapping using 150 Gy14 × 9930 recombinant inbred lines and 1043 F2 individuals delimited the cla locus into a 32 kb region in cucumber Chromosome 5 with three predicted genes. Multiple lines of evidence suggested that the cucumber STAYGREEN (CsSGR) gene is a candidate for the anthracnose resistance locus. A single nucleotide mutation in the third exon of CsSGR resulted in the substitution of Glutamine in 9930 to Arginine in Gy14 in CsSGR protein which seems responsible for the differential anthracnose inoculation responses between Gy14 and 9930. Quantitative real-time PCR analysis indicated that CsSGR was significantly upregulated upon anthracnose pathogen inoculation in the susceptible 9930, while its expression was much lower in the resistant Gy14. Investigation of allelic diversities in natural cucumber populations revealed that the resistance allele in almost all improved cultivars or breeding lines of the U.S. origin was derived from PI 197087. This work reveals an unknown function for the highly conserved STAYGREEN (SGR) family genes for host disease resistance in plants.

PMID:
29680862
DOI:
10.1007/s00122-018-3099-1
[Indexed for MEDLINE]

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