Seed-borne nature of mungbean yellow mosaic India virus in mung bean (Vigna radiata L.) occurs due to cultivar and sowing date variation

Abstract

Mungbean yellow mosaic India virus (MYMIV) is the major viral species responsible for yellow mosaic disease in Northern India, belonging to the genus Begomovirus, family Geminiviridae. Recently, a few of the begomovirus species were reported to be seed-transmissible which is a disputed character for begomoviruses. In the present study, the possibility of MYMIV transmission was assessed through seed collected from field-infected mungbean cultivars Pusa1371 and Pusa 9531 using serological, molecular and progeny assays for three continuous seasons with three different sowing dates. Detection of MYMIV from infected seed through direct antigen-coated enzyme-linked immunosorbent assay (DAC-ELISA) showed very low absorbance values in the range of 0.23- 0.30 at 405 nm. Polymerase chain reaction (PCR) using the total DNA from the whole seed resulted in the amplicon size of 602bp and 850bp corresponding to DNA-A and DNA-B regions, respectively. Inconsistent amplification was observed only in the whole seed and seed coat, but not in cotyledons and embryonic axes of the cultivars with the first and second sowing of kharif/ rainy season. No amplification was observed with the seed harvested from the third sowing of kharif 2021 and spring-summer of 2021 and 2022. The radicle region of the seedlings tested negative through PCR with MYMIV-specific primers. No visible symptoms were observed in 1800 raised seedlings from the MYMIV-infected seed of each cultivar. Testing of 1350 susceptible and 450 resistant cultivar seedlings through DAC-ELISA and 225 susceptible and 45 resistant cultivars through PCR showed the absence of MYMIV from the raised seedlings. Based on the results of DAC-ELISA, PCR and grow-out experiments, it was concluded that MYMIV may be seed-borne in nature but not seed-transmitted in the tested mungbean cultivars.