Genetics of begomovirus resistance in Cucurbita moschata Duchesne: A novel resistant source PVR-1343

Whitefly transmitted begomoviruses are the most destructive virus(es) that causes quantitative and qualitative losses to pumpkin (Cucurbita moschata) crop worldwide. In present study we have molecularly characterized three types of viral infections, which were caused by squash leaf curl China virus (SLCCNV), tomato leaf curl New Delhi virus (ToLCNDV), and their mixed infection (MI-Sq/To). Screening of diverse germplasm through whitefly (Bemisia tabaci mitotype Asia II) mediated artificial inoculation and PCR confirmed the 'PVR-1343' genotype as a resistance source against identified begomoviruses. To understand the genetic control of begomovirus resistant gene(s), segregating populations derived from crosses of 'PVR-1343' and four susceptible genotypes (MVSR-6711, Punjab Samrat, MBN-6242 and P-278) inoculated with SLCCNV, ToLCNDV and MI-Sq/To by whitefly in closed environment for three consecutive years (2018-2020). Disease scoring at 75 days after sowing rendered all F1 progenies as susceptible indicating recessive nature of resistance with no maternal or cytoplasmic effects. Chi-square analysis indicated a good fit of 9(S):3(MS):3(MR):1(R) ratio in F2 progenies of all crosses. Backcross of the F1's to the resistant parent segregated into 1:1:1:1 ratio, while all progeny were susceptible in backcross of the F1's with susceptible parent. 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 digenic recessive genes. Moreover, F2:3 progenies resistant to SLCCNV were also resistant to ToLCNDV and MI-Sq/To and vice versa, suggesting that common or tightly linked gene(s) might be involved in resistance to both viruses.