EPIDEMIOLOGY AND MANAGEMENT OF YELLOW MOSAIC DISEASE INFECTING BLACKGRAM (Vigna mungo (L.) HEPPER)
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Date
2023-12-07
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Acharya N G Ranga Agricultural University
Abstract
In the present investigation on “Epidemiology and management of yellow mosaic disease infecting blackgram (Vigna mungo (L.) Hepper)”, four major blackgram growing districts viz., Krishna, Guntur, West Godavari and Prakasam of Andhra Pradesh were surveyed for the incidence of yellow mosaic disease (YMD). Disease incidence among various districts ranged from 14.58% to 23.04% indicating the impact of disease.
Fifteen weed species, showing typical mosaic symptoms were collected out of which six weeds viz., Abelmoschus moschatus, Ageratum conyzoides, Amaranthus viridis, Desmodium laxiflorum, Parthenium hysterophorus and Vigna trilobata, were found positive for Mungbean yellow mosaic India virus (MYMIV). First time, A. moschatus and D. laxiflorum were reported to have infected with Mungbean yellow mosaic India virus when confirmed using PCR detection. Association of betasatellite ( ̴1.3 kb) and MYMIV in A. moschatus was also reported for the first time, which defines the movement of MYMIV into new hosts and association with the already existing betasatellites.
Molecular characterization based on coat protein revealed that the test isolates viz., YMV-KR from Krishna district (MZ475993), YMV-GN from Guntur district (MZ475994), YMV-WG from West Godavari district (MZ475996), YMV-PR from Prakasam district (MZ475995), YMV-ABEL from A. moschatus (MZ475997) and YMV-DES from D. laxiflorum (MZ475998) belong to MYMIV and none of them showed positive to MYMV. Hence it was concluded that YMD isolates of blackgram in surveyed areas of Andhra Pradesh were closely related to MYMIV (old world geminiviruses) than MYMV (New world geminiviruses).
The sequence analysis of six isolates using SDTv1.2 revealed that YMV-GN and YMV-DES shared 99.58% homology, which was the highest among test isolates
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whereas, least homology of 94.85% was found between YMV-PR and YMV-WG. Isolates of the two weed species YMV-DES and YMV-ABEL shared an identity of 99.30% at nucleotide level. The isolates collected from crop species i.e., YMV-KR, YMV-GN, YMV-WG, YMV-PR shared a nucleotide similarity of 94.85-97.77%. Phylogenic analysis based on coat protein revealed that two isolates from Krishna district and West Godavari district varied with isolates collected from Guntur and Prakasam.
The whole genome characterization of causal organism of YMD revealed a novel recombinant isolate (YMV-BG-BPT) from blackgram in Andhra Pradesh. The association of a bipartite begomovirus with the disease was confirmed by sequence analyses of the cloned full-length genome. The sequence analysis of DNA-A (MZ235792) of YMV-BG-BPT showed maximum of 99.12% similarity at nucleotide level with Mungbean yellow mosaic India virus (MYMIV) isolate reported from Tamil Nadu, India (KC911719), which was also confirmed by clustering pattern in phylogenic analysis. The sequence analysis of DNA-B (MZ356197) showed 95.79% with Mungbean yellow mosaic virus (MYMV) isolate reported from Tamil Nadu (KP319016) and 95.05% with Mungbean yellow mosaic India virus (MYMIV) isolate reported from Karnataka (MT027037). The huge variation in DNA-B, was further confirmed by detecting a recombinant event in the intergenic region (IR), region coding for nuclear shuttle protein and movement protein in which MYMV-BG-AP-IND (KF928962) and MYMIV-GG-CH-IND (MN020536) have been identified as major and minor parents, respectively. To the best of our knowledge, this was the first molecular confirmation and characterization of blackgram infecting MYMIV with a recombinant DNA-B in Andhra Pradesh, India.
During epidemiological studies (2019-2021), among the three sowings, Min T had showed negative correlation with both whitefly population and disease severity during first and second sowing. However, in the third sowing negative correlation with Min T was taken over by RHE in terms of whitefly population while the same was taken over by RHM in terms of disease severity. During the entire study, whitefly population had shown positive correlation with disease severity. The epidemiological studies conducted during present investigation indicated that first sowing of blackgram (2nd fortnight of October) had lesser YMD severity while late sowings favoured development of disease due to favourable weather conditions for buildup of whitefly and thereby the disease.
Management studies with different insecticides and botanicals revealed that flonicamid 50 WG @ 0.4 g l-1 was effective in reducing whitefly population with a mean reduction of 67.52% and 61.01% at first and second spray, respectively over control, while among the botanicals cotton seed extract 5% (Gossypium herbaceum) was found effective with a mean whitefly reduction of 22.83% and 22.09% at first and second spray respectively over control. Among chemicals, flonicamid 50 WG @ 0.4 g l-1 treatment recorded least disease incidence (72.33%) and severity (68.24%), while the botanical ramaphal leaf extract 5% (Annona reticulata) has recorded with least disease incidence (85.02%) and severity (55.44%). Among all the treatments, AUDPC was highest in the control (1313.27) while least was recorded in flonicamid 50 WG @ 0.4 g l-1 (653.04). Among the botanicals, ramaphal leaf extract 5% showed least AUDPC (1006.83) when compared to turmeric corm extract 5% (1091.40) and cotton seed extract 5% (1096.44). Highest yield was recorded in flonicamid treated plots (537.39 kg ha-1) followed by acetamiprid (453.33 kg ha-1) whereas, among the botanicals ramaphal leaf extract treated plots recorded a yield of 340 kg ha-1.