Inheritance and molecular mapping of gene(s) associated with yellow vein mosaic virus disease (YVMVD) resistance in pumpkin (Cucurbita moschata Duch. ex Poir)
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Date
2022
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Punjab Agricultural University, Ludhiana
Abstract
Worldwide begomoviruses causative diseases are major reason of quantitative and qualitative losses in pumpkin. The three types of viral symptoms were molecularly characterized as SqLCCV, ToLCNDV and their mixed infection (MI-Sq/To). Artificial screening, histopathological study and PCR confirmed PVR-1343 as a novel resistant source against both begomoviruses. To understand the inheritance and mapping of begomovirus resistant gene(s), segregating populations between PVR-1343 and five susceptible lines (P-135, P-6711, Punjab Samrat, MBN-6242 and P-278) were developed and artificially inoculated with Bemisia tabaci Asia II strain against both viruses and their mixed infection in enclosed structures for three consecutive years (2018-2020). Disease scoring at 75DAS rendered all F1 progenies as susceptible indicating recessive nature of resistance with no maternal or cytoplasmic effects. Chi-square analysis showed best fit of 9(S):3(MS):3(MR):1(R) and 1(S):1(MS):1(MR):1(R) ratio in F2 and backcross with resistant parent respectively. Phenotypic segregation ratio of F2:3 confirmed the F2 genotypic ratio of 1:2:2:4:1:2:1:2:1. This substantiated that multiple begomovirus resistance in PVR-1343 is controlled by a digenic recessive gene. Moreover, F2:3 progenies resistant to SqLCCV were also resistant to ToLCNDV and MI-Sq/To and vice versa, suggesting that common or tightly linked gene(s) are involved in resistance to both viruses. To map these genes, WGRS coupled with QTLseq of two extreme bulks (resistant and susceptible) of cross PVR-1343×P-135 along with parents were employed and two genomic regions viz., qMI-Sq/To7.1 on chromosome 7 (3.18 to 4.70Mb) and qMI-Sq/To17.1 on chromosome 17 (7.30 to 8.17Mb) were identified. Nine polymorphic SNPs identified within the highly significant qMI-Sq/To7.1 region were converted into KASP marker. The KASP genotyping of 177 F2 individuals narrowed down the qMI-Sq/To7.1 interval to a 103Kb region flanked by Cmo3914729 and Cmo4018182 KASP markers. One of the flanking SNP (Cmo4018182 KASP marker) imparting resistance against MI-Sq/To, accurately predicted the disease reaction of 91 per cent of diverse Cucurbita genotypes. This SNP showed nonsynonym substitution in the coding region of putative candidate syntaxin-121 protein and might be responsible for diminishing or abolishing the viral infections. This study has thus, seeded the path for marker assisted selection for efficient introgression of resistance into elite C. moschata lines and providing a viewpoint for gene cloning.
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Verma, Neha (2022). Inheritance and molecular mapping of gene(s) associated with yellow vein mosaic virus disease (YVMVD) resistance in pumpkin (Cucurbita moschata Duch. ex Poir) (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.