<div>Background: The yellow mosaic disease (YMD) creates a major hindrance and known to affect a number of grain leguminous crops in the Indian sub-continent. However, blackgram (Vigna mungo L.) is the most important grain legume crop which is affected widely by this disease. The disease is caused by a single stranded DNA containing begomovirus viz., Yellow mosaic virus (YMV) which is mainly transmitted through whitefly (Bemisia tabaci Genn.). Symptoms include severe patho-physiological alterations characterized by the presence of bright chlorotic yellow patches interspersed with green areas on leaf lamina. The present study was aimed to determine the variability among disease causing agents in six different geographical isolates representing four states viz. Andhra Pradesh, Karnataka, Odisha and Telangana states of southern India during the 2019 rabi season. 
 
Methods: The variability of YMV associated with YMD of blackgram was studied based on molecular characterization of partial DNA-A coat protein gene with subsequent nucleotide sequencing and phylogenetic tree construction. 
 
Result: The synthetic primers designed for the partial DNA-A segment forms a distinct viral gene specific PCR product. The band size corresponding to CP ~704 bp was obtained for MYMV, whereas CP ~500 bp gene band was obtained for MYMIV. Further, phylogenetic analysis based on partial DNA-A gene sequences of six isolates with other isolates from GenBank formed into two unique clusters viz., MYMV and MYMIV. Overall, our study confirming that the begomovirus causing YMD of blackgram in southern India is explored to be as strains of MYMV and MYMIV.</div>

Molecular Variability of Yellow Mosaic Virus (YMV) of Blackgram in Southern India

Background: Yellow mosaic disease (YMD), caused by the Mungbean yellow mosaic India virus (MYMIV), seriously affects soybean production in the central and northern regions of India. 
 
Methods: The present investigation was conducted to reveal the relation among the fluctuating population of whiteflies, YMD progression, meteorological parameters and crop age in four varieties, i.e. 335, JS 20-34, NRC 86 and MACS 1520, at J.N.K.V.V., Jabalpur, during kharif 2021 (June to September). The whitefly population, by visual and cage and YMD severity were recorded at weekly intervals.&nbsp; 
 
Result: Whiteflies first appeared 13 days after sowing (27th SMW) and reached a peak of 7.73 per plant (cage) and 3.29 per trifoliate (visual) at 29th SMW (July, 16-22). During this maximum and minimum temperature, morning and evening RH were 33.4 and 25.4&deg;C, 84.10 and 70.0 %, respectively. Whiteflies on JS 335 (0.639* and 0.635*) and MACS 1520 (0.672* and 0.639*) significantly positively correlated with maximum temperature in visual and cage counts. Wind speed exhibited a significant negative relation with a whitefly count of JS 335 (-0.753*) and MACS 1520 (-0.764*). YMD initiated (28th SMW) at high temperature (max 33.3&deg;C and min 25.1&deg;C), low rainfall (33.2 mm), less humid conditions (evening 58.3-morning 85.1 %) and presence of whitefly. In contrast, at the time of maximum disease progression (32nd SMW), comparative low temperature (max 28.5 and min 24.2&deg;C) and high humid conditions (evening 79.0-morning 90.0) prevailed. Among the four varieties, maximum disease severity was recorded in JS 20-34 (48.16%). The corresponding week&rsquo;s maximum temp (0.771**) and sunshine hours (0.792**) were negatively significant and evening RH (0.717*) and wind speed (0.708*) had a positively significant relation with mean YMD progression. A similar significant association was also obtained between the previous week&cent;s parameters and disease. YMD and whitefly exhibited a negative, non-significant association. Crop age also linked non-significantly with YMD progression. The present findings could be utilized to predict vector and YMD and to formulate appropriate management strategies for both.

Relationship between Whiteflies, Yellow Mosaic Severity, Weather and Crop Age in Soybean

<div>Background: Yellow mosaic disease (YMD) caused by Mungbean Yellow Mosaic Virus (MYMV) is one of the most destructive biotic constraints for production in urdbean. Development and introduction of resistant cultivars with high seed yield is&nbsp; considered as the most economical and eco-friendly option to manage YMD, for which understanding the gene action controlling the inheritance of different traits along with YMD resistance is an important requirement. 
 
Methods: Material comprised of four diverse genotypes (TU 94-2, PU 31, IPU 94-1 and&nbsp; LBG 623), six F1s, six BC1s and six BC2s and six F2s. These six generations of all the six crosses were evaluated for various yield related traits in rabi, 2020-21 and phenotyped for YMD in summer, 2021 at Lam, Guntur, Andhra Pradesh which is hotspot for YMD. 
 
Result: Inadequacy of additive-dominant model for all most all traits including YMD except for test weight was observed. It was found that, [l] type of non-allelic interaction was observed to be predominant for majority of the traits. Further, the existence of duplicate type of epistasis in the inheritance was evident at least in few crosses for all the traits (except days to maturity). The duplicate epistasis will reduce the variation in F2 and subsequent generations, thereby hinder the pace of the progress through selection.</div>

Gene Effects of Quantitative Traits through Six Parameter Model of Generation Mean Analysis in Black Gram [Vigna mungo (L.) Hepper]

<div>Background: Yellow mosaic disease (YMD) transmitted by white fly, Bemisia tabaci is the most persistent and devastating biotic stress worldwide and in India resulting the reduced productivity of mungbean. At the same time the yield levels in mungbean reached a plateau, which emphasizes the importance of varieties with improved productivity. 
 
Methods: In the present investigation, to address this urgent requirement of YMD resistant high yielding varieties, six-parameter model of generation mean analysis was employed for proper understanding of the genetic architecture and gene actions. Susceptible genotype MGG 385 was crossed with four resistant genotypes (LGG 607, LGG 630, WGG 42 and PM 5) to produce respective F1s (during rabi, 2018-19), BC1s, BC2s (during summer, 2019) and F2s (during kharif, 2019). These generations of the four crosses were evaluated for various yield related traits in rabi, 2019-20 and phenotyped for YMD in summer, 2020 at Lam, Guntur, Andhra Pradesh which is hotspot for YMD. 
 
Result: The scaling tests and joint scaling test indicated the inadequacy of Additive-dominant model for all most all traits including YMD except for branches per plant and pods per cluster. The study revealed the importance of non-allelic interactions in the inheritance of majority of traits including YMD. Among the non-allelic interactions, [l] type of interaction is predominant. Further, the control of duplicate type of epistasis in the inheritance is evident at least in few crosses for all the traits (except grain yield per plant) that had inadequacy for additive-dominant model, which hinders the pace of the progress through selection. In presence of inter-allelic interaction with such duplicate type of epistasis, population approach in self-pollinated crops, which is similar to recurrent selection in cross pollinated crops or biparental mating followed by conventional selection in the later generations should be adopted for identifying desirable segregants.</div>

Understanding the Genetic Architecture and Gene Actions Involved in the Inheritance of Yellow Mosaic Disease and Other Yield Related Traits in Mungbean [Vigna radiata (L.) Wilczek]

<div>Background: Dry root rot (DRR), yellow mosaic disease (YMD) and stem necrosis diseases are inflicting the economic losses in urdbean. Information on the interrelation of morphological and biochemical parameters of the urdbean cultivars with the disease resistance is scarce.&nbsp; 
 
Methods: Thirty nine cultivars of urdbean were screened in the field for their resistance to DRR, YMD and stem necrosis diseases during Rabi, 2019-2020. The incidence of the diseases is compared with the morphological characters viz., trichome density, leaf thickness, root thickness and biochemical composition viz., total free amino acids, total soluble sugars and phenol content of cultivars.&nbsp; 
 
Result: Cultivar GBG 103 was found resistant to DRR and YMD with the maximum amount of trichome density. No cultivar was found resistant to stem necrosis under field conditions. Correlation analysis revealed the positive correlation of phenol content with the DRR incidence; trichome density and total soluble sugars with YMD incidence. Albeit the leaf thickness and total free amino acid content of the cultivars were negatively correlated with the incidence of the DRR, YMD and stem necrosis diseases.</div>

Scouting for Multiple Disease Resistance in Urdbean

<div>Mungbean yellow mosaic virus [Urdbean: New Delhi: 2011] Accession no. JQ398669.1, was found to be prevalent in both summer and kharif season causing Yellow Mosaic Disease (YMD) of mungbean. Since similar strain was observed in both the seasons, the short duration interspecific derivative lines of mungbean suitable for summer season were evaluated for YMD resistance in kharif season- a highly favourable environment for YMD epidemics during 2014-2016. Out of fourteen lines showing stable resistant reaction, few lines promising for other economically important traits were selected and again evaluated by whitefly mediated artificial inoculation technique for confirmation of resistance during 2017. The selected promising interspecific derivative lines showed no YMD symptoms except SML 1829. SML 1827 derived from interspecific cross between mungbean and rice bean showed highest yield among all interspecific derivatives. Further, rice bean specific segments were also identified in SML 1827 with SSR markers.</div>

<div>Deployment of yellow mosaic disease resistance in mungbean [Vigna radiata (L.) Wilczek] through interspecific hybridization</div>

Background: Yellow mosaic disease (YMD) is one of the most severe and widespread constraint for the cultivation of soybean. Given that no comprehensive data on the status of soybean yellow mosaic disease in Northern Hills and North Western Plains of India is present, a detailed investigation was undertaken for three years to study the prevalence of the disease in the region and to characterize the pathogen. 
&nbsp; 
Methods: Towards Kharif end, a three year (2018-2020) farmer field survey (76 villages) was carried out to assess the YMD distribution in the major soybean growing areas Northern Hills and North Western Plains of India. The variability of yellow mosaic virus associated with YMD of soybean was studied based on molecular characterization of partial DNA-A coat protein gene and DNA-B movement protein with subsequent nucleotide sequencing and phylogenetic tree construction. 
 
Result: The results revealed that YMD is prevalent in the plains, whereas the disease was undetectable in the Hills. In the plains, the mean disease incidence ranged from 25.40% in 2019 to 16.78% in 2020. Moreover, disease incidence (r = -0.748) had negative and significant (p&lt;0.0001) correlation with altitude. The phylogenetic studies revealed that the virus inciting the yellow mosaic in soybean in Tarai region had closest relationship with Mungbean yellow mosaic India virus (MYMIV). It shared more than 96 per cent sequence identity with other MYMIV isolates reported earlier within the country and abroad and hence, was designated as an isolate of MYMIV.

Geographical Distribution and Molecular Characterization of Begomovirus Infecting Soybean [Glycine max (L.) Merr.] in Northern Hills and North Western Plains of India

<div style="text-align:justify">Background: Vigna mungo (Blackgram) is the major pulse crop cultivated in the Indian sub-continent. It is highly prone to yellow mosaic disease (YMD), which is widespread problem because all cultivated varieties are susceptible to the YMD in Andhra Pradesh state. The presence of two species of begomovirus i.e. Mungbean yellow mosaic virus (MYMV) and Mungbean yellow mosaic India virus (MYMIV) with YMD was reported in Andhra Pradesh. The current study was aimed to develop simple method of viral dimer clone construction and identifying the resistant blackgram genotypes against two species of begomovirus (MYMV and MYMIV) by agroinoculation technique. 
&nbsp; 
Methods: In this study, we standardize the rolling circle amplification (RCA) based viral dimer clone construction (MYMV DNA-A, MYMV DNA-B and MYMIV DNA-A) and constructed viral dimer clones were used to transform Agrobacterium tumefaciens EHA105 cells through freeze-thaw technique. Sprouted seed method of agroinoculation screening was conducted. 
 
Result: Total 45 blackgram genotypes were screened by sprouted seed method of agroinoculation with two combinations of viral dimeric constructs (MYMV-TPT-A+MYMV-TPT-B and MYMIV-TPT-A+MYMV-TPT-B). Twenty four genotypes offered resistant against MYMV infection and twenty three genotypes were resistant to MYMIV infection. Total 17 genotypes offered resistance to both species of virus (MYMV andMYMIV) associated with YMD.</div>

Construction of Full-length Dimer Clones of Yellow Mosaic Virus and Screening of Blackgram Germplasm using Agroinoculation

<div>Background: Pulse crops have a unique position in sustainable crop production as they provide highly nutritive food and keep the soil alive as well as productive. They play an important role in the Indian agriculture economy being the major source of protein in Indian dietary. Due to its more luxurious growth and more vegetative canopy, number of insect pests and diseases attack from seedling to maturity stage especially sucking pests like whitefly (Bemisia tabaci Genn.), which is the vector of the drastic disease, yellow mosaic virus disease (YMD) and cause losses ranging from 30-80% per cent. 
 
Methods: The field experiment on the management of whitefly and yellow mosaic disease (YMD), was conducted by integrating different combination of insecticides and yellow sticky trap during Kharif, 2018 and 2019 at instructional farm of VBKVK, Udaipur. Seven treatments comprising of different combinations of seed treatments at the time of sowing, foliar spray at 30 and 45 DAG and yellow sticky traps were evaluated.&nbsp; 
 
Result: Among the different treatments, seed treatment with Imidacloprid 600 FS @ 5 ml/kg, first foliar spray of Diafenthuron 50 WP @ 0.1% and second foliar spray with Acetamiprid 20 SP @ 0.5 g/l at 30 and 45 DAS respectively + yellow sticky trap resulted in significantly less YMD incidence (18.91%) and the minimum mean whitefly population and highest seed yield of blackgram. The above treatment was followed by seed treatment with Imidacloprid 600 FS @ 5 ml/kg and two foliar spray of Acetamiprid 20 SP @ 0.5 g/l at 30 and 45 DAS + yellow sticky trap, which recorded 20.31% disease incidence of YMD and mean whitefly population of (3.77 and 1.44/plant, respectively after first and second spray) and black gram yield of 10.01 q/ha.&nbsp;</div>

Management of Whitefly, Bemisia tabaci (Genn.) and Yellow Mosaic Virus Disease Infesting Blackgram, Vigna mungo (Linn)

<div>Background: Yellow mosaic disease (YMD) caused by begomoviruses transmitted through the insect vector Bemisia tabaci poses a serious threat to the production of legume crops. 
 
Methods: Season-long surveys were carried out for YMD occurrence in six different legume crops and associated natural weeds both symptomatic and asymptomatic across the districts of southern Karnataka, India. The samples were analyzed through RCA PCR using specific primer pairs. 
 
Result: Up to 94.1 per cent YMD incidence was recorded and nine weed species were commonly found associated with legume crops. The weeds viz., Ageratum conyzoides, Alternanthera sessilis, Commelina benghalensis and Euphorbia geniculata were abundantly found in the surveyed regions. The weeds were both symptomatic and asymptomatic. Rolling circle amplification coupled polymerase chain reaction method was employed to detect yellow mosaic virus in asymptomatic weeds. Phylogenetic analysis based on the sequences of PCR amplified products of weeds and symptomatic legumes revealed a close clustering of the weed samples with horsegram yellow mosaic virus, legume yellow mosaic virus and mungbean yellow mosaic virus. Overall, our data suggests the role of weed species associated with legume crops as alternative/collateral hosts of begomoviruses and their role in the epidemiology of yellow mosaic disease.</div>