Understanding VBN 11 blackgram [Vigna mungo (L.) Hepper] and the epidemic of yellow mosaic virus (YMV): New report

Introduction

Blackgram (Vigna mungo L.), a vital pulse crop with 22 chromosomes (2n=22), holds significant importance across tropical and subtropical regions. In the Indian subcontinent, it stands as the third most cultivated pulse, trailing only chickpea and pigeonpea (Nair et al., 2024) [11] . India is a leading global producer, harvesting 3.06 million tons from 5.60 million hectares. Often hailed as the "king of pulses" for its delicious taste and rich nutritional profile, blackgram is a powerhouse of essential nutrients. It boasts 25-26% protein, 60% carbohydrates, 1.5% fat, and a good array of minerals, amino acids, and vitamins (Kumar et al., 2024) [8] . A unique advantage of black gram is its ability to perform symbiotic nitrogen fixation, enriching the soil. This versatile crop is typically short-duration, flowering within 30-60 days and maturing within 60-90 days (Pooja et al., 2023) [12] . However, its productivity is severely hampered by various factors, with Yellow Mosaic Disease (YMD) being the most destructive (Aryal et al., 2022) [2] . Caused by the Mungbean Yellow Mosaic Virus (MYMV), this disease can lead to devastating yield losses of up to 85-100% in urdbean, depending on the infection's stage and severity (Marabi et al., 2021) [10] . By the examination of multi-location trials, the culture VBG 12-062 was screened against major diseases from 2017 to 2018 and showed a highly resistant reaction to MYMV disease. Based on the improved performance of VBG 12-062, it was released as VBN 11. Initially, it has documented as resistant nature with high yield profiling with 899kg/ha in all seasons of cultivation in Tamil Nadu (Geetha et al., 2020) [3] . But later days, it become change as resistant to little by little susceptible one depending upon addressing of mutations, twisting of eco-adaption, emergence of new weeds for alternate host for viral survivor and pest dynamics (Thabrez and Vineeth, 2024) [14] . Moreover, viral diseases in plants present a real headache for farmers worldwide, wiping out harvests and putting food supplies in disturbed (Varanda et al., 2021) [16] . To fight back, breeders and scientists create virus-resistant crops using traditional cross-breeding, modern gene editing and handy DNA markers to speed up selection (Hinge et al., 2021) [4] . Each new line is tuned to shrug off a particular virus, cutting downtime in the field when disease normally strikes. Yet that shield doesn't always last because viruses are quick to change, and resistance among that shield wears thin over time (Vineeth et al., 2023) [17] .

Mutations, constant pressure to survive, and even the climate around them push the virus to find weak spots in the crop (Tsai et al., 2022) [15] . When that happens, plants once thought safe start wilting again, and the same viral wave rolls through the field (Jones, 2021) [5] . Loss of resistance can happen on its own or be nudged along by lab tricks, RNA knockouts, or simple gene loss in successive generations (Taliansky et al., 2021) [13] . Pinpointing how these switches occur matters, because it guides a broad toolbox that mixes resistant varieties, rotation, and all-in pest control for longer-lasting protection (Kumar et al., 2024) [9] . Studying the initial inner workings of resistance, therefore, remains a must-do task in the race to keep crops healthy by disease prevalence (Kreuze and Valkonen, 2017) [7] . Keeping this background the study was carried out for the yellow mosaic virus impact in VBN 11.

Materials and Methods

Seed source

The studying seed material (VBN 11) was obtained from National Pulse Research Centre, Vamban.

Location and season

The field was selected and prepared at the Sugarcane Research Station at Cuddalore. Seeds are sown at 25×10 cm spacing with 5 cm depth under well-drained black soil. The sowing process takes place in Rabi from 2023 to 24.

Disease assessment

Based on the symptomatology of plants, the incidence of yellow mosaic was recorded in the field at 25 days after sowing. It was calculated by the formula (Kasi Rao et al., 2020) [6] .

Results and Discussion

During this study, yellow mosaic disease incidence was recorded from 25 days after sowing (DAS). Field observations revealed a disease incidence of 70-77% in VBN 11 (Fig 1). Previously, VBN 11 had been reported as resistant to yellow mosaic disease by Geetha et al. (2020) [3] . However, in recent years, a combination of agroclimatic factors, repeated monocropping, and the annual emergence of new weeds have contributed to its increased susceptibility (Anikina et al., 2023) [1] .

Conclusion

Based on the experiment's results, VBN 11 exhibited a susceptible nature to yellow mosaic disease during the Rabi 2023 season, a shift from its previously resistant status. This transformation likely occurred due to factors such as inadequate monitoring, adaptation to new agroclimatic conditions, climate change, and the emergence of mutated virus strains, new crop varieties, and weeds. Therefore, future breeding programs must focus on developing resistance through multi-potential, climatesmart agricultural approaches.

References

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