Association Mapping for Yield Attributing Traits and Yellow Mosaic Disease Resistance in Mung Bean [Vigna radiata (L.) Wilczek]

Mung bean [Vigna radiata (L.) Wilczek] is an important short-duration grain legume widely known for its nutritional, soil ameliorative, and cropping system intensification properties. This study aims at evaluating genetic diversity among mung bean genotypes and detecting genomic regions associated with various yield attributing traits and yellow mosaic disease (YMD) resistance by association mapping. A panel of 80 cultivars and advanced breeding lines was evaluated for 10 yield-related and YMD resistance traits during kharif (monsoon) and summer seasons of 2018–2019 and 2019–2020. A total of 164 genome-wide simple sequence repeat (SSR) markers were initially screened, out of which 89 were found polymorphic which generated 317 polymorphic alleles with an average of 3.56 alleles per SSR locus. The number of alleles at each locus varied from 2 to 7. The population genetic structure analysis grouped different genotypes in three major clusters and three genetically distinct subpopulations (SPs) (i.e., SP-1, SP-2, and SP-3) with one admixture subpopulation (SP-4). Both cluster and population genetic structure analysis categorized the advanced mung bean genotypes in a single group/SP and the released varieties in other groups/SPs, suggesting that the studied genotypes may have common ancestral history at some level. The population genetic structure was also in agreement with the genetic diversity analysis. The estimate of the average degree of linkage disequilibrium (LD) present at the genome level in 80 mung bean genotypes unveiled significant LD blocks. Over the four seasons, 10 marker-trait associations were observed significant for YMD and four seed yield (SY)-related traits viz., days to flowering, days to maturity, plant height, and number of pods per plant using the mixed linear model (MLM) method. These associations may be useful for marker-assisted mung bean yield improvement programs and YMD resistance.

Survey for Yellow Mosaic Disease Occurring on Blackgram [Vigna mungo (L.) Hepper] and Weed Hosts in Four Major Blackgram Growing Districts of Andhra Pradesh and Characterization of Associated Viruses using Coat Protein Gene

Background: Yellow mosaic disease (YMD) caused by Yellow mosaic virus is one of the major constraints in the pulse production in Andhra Pradesh (A.P.) due to fast evolution of strains, like Mungbean yellow mosaic India virus (MYMIV). Keeping this in view, a survey was undertaken in the major blackgram growing districts of A.P. to know the YMD incidence in blackgram and weed hosts and were characterized based on genetic features by comparing with other YMV isolates from different hosts and locations across the world. Methods: Roving survey was conducted during rabi 2019-20 in major blackgram growing districts of A.P. viz., Krishna, Guntur, West Godavari and Prakasam districts for YMD incidence. Blackgram plants showing characteristic symptoms were collected as representative samples from each mandal along with the suspected weed plants and were subjected to amplification using coat protein (CP) specific primers followed by molecular characterization. Phylogenetic tree for coat protein (CP) gene was constructed using aligned sequences with 1000 bootstrap replicates following neighbor-joining phylogeny. Result: Out of the four districts surveyed, the highest disease incidence was recorded at Machavaram village of Prakasam district (43.22%), whereas least disease incidence was recorded at Chinaganjam village of Praksam district (2.4%). Six weeds viz., Ageratum conyzoides, Amaranthus viridis, Parthenium hysterophporus, Vigna trilobata, Abelmoscus moschatus, Desmodium laxiflorum have showed positive result in PCR amplification with MYMIV specific coat protein primers. Four isolates from blackgram samples and two from weed plants shared 94.85 to 99.58% nucleotide identity among themselves.

Identification and Molecular Characterization of a Novel Hordeivirus Associated With Yellow Mosaic Disease of Privet (Ligustrum vulgare) in Europe

Wild plants serve as a large reservoir of known and yet-unknown viruses and as a source of viral pathogens of cultivated plants. Yellow mosaic disease of forest shrub Ligustrum vulgare (privet) was recurrently observed in Europe for more than 100 years. Using a universal virus identification approach based on deep sequencing and de novo assembly of viral small interfering (si)RNAs we identified a causative agent of this disease in Switzerland and reconstructed its complete 3-segmented RNA genome. Notably, a short 3′-terminal common region (CR) attached to each segment via a ∼53–71 nucleotide poly(A) tract, as determined by RT-PCR sequencing, was initially identified as an orphan siRNA contig with conserved tRNA-like secondary structure. Phylogenomic analysis classified this virus as a novel member in the genus Hordeivirus of family Virgaviridae, which we named ligustrum mosaic virus (LigMV). Similar to other hordeiviruses, LigMV formed rod-shape virions (visualized by electron microscopy), was transmitted through seeds and could also be mechanically transmitted to herbaceous hosts Chenopodium quinoa and Nicotiana benthamiana. Blot hybridization analysis identified genomic and subgenomic RNAs, sharing the 3′-CR and likely serving as monocistronic mRNAs for seven evolutionarily-conserved viral proteins including two subunits of viral RNA-dependent RNA polymerase, coat protein, triple gene block proteins mediating viral movement and cysteine-rich suppressor of RNA silencing. Analysis of size, polarity, and hotspot profiles of viral siRNAs suggested that they are produced by the plant antiviral Dicer-like (DCL) proteins DCL2 and DCL4 processing double-stranded intermediates of genomic RNA replication. Whole genome sequencing of French and Austrian isolates of LigMV revealed its genetic stability over a wide geographic range (>99% nucleotide identity to Swiss isolates and each other), suggesting its persistence and spread in Europe via seed dispersal.

Distribution, host range and detection of seed-borne yellow mosaic disease on yardlong beans (Vigna unguiculata subsp. sesquipedalis L.) in the special region of Yogyakarta, Indonesia

Mulyadi D, Sulandari S, Hartono S, Somowiyarjo S. 2021. Distribution, host range and detection of seed-borne yellow mosaic disease on yardlong beans (Vigna unguiculata subsp. sesquipedalis L.) in the special region of Yogyakarta, Indonesia. Biodiversitas 22: 3949-3957. Yellow mosaic disease found in legumes is caused by Mungbean yellow mosaic India virus (MYMIV). MYMIV has been reported to cause yellow mosaic infection on yardlong beans (Vigna unguiculata subsp. Sesquipedalis L.) in various regions of Indonesia and has resulted in major yield loss. Symptoms of mosaic and yellowing are found in the leaves and on the pods, which means that the virus may be seed-borne. The purpose of this study was to identify the distribution, host range of pathogens, and to investigate whether yellow mosaic virus was seed-borne or not. Sample collection, disease incidence and severity observations were done at yardlong bean fields in the District of Sleman, Bantul, and Kulon Progo. Samples were tested using PCR (Polymerase Chain Reaction) and phylogenetic tree analysis. Host range was tested by inoculating MYMIV using Bemisia tabaci to test plants. Two types of seeds were used in seed-borne tests, i.e. certified commercial seeds and malformed pods from infected plants. Results showed that yellow mosaic virus was found in all observation sites. Highest disease incidence was recorded in Sleman (50%) followed by Kulon Progo (45%) and Bantul (23%). Whereas 45.89%, 41.29% and 39.83%, disease severity was noted in Sleman, Kulon Progo and Bantul, respectively phylogenetic tree analysis showed that isolates used in this study were similar to other Indonesian isolates. Host range test revealed that yardlong beans, mungbeans (Vigna radiata L.), sesame seeds (Sesamum indicum L.), cucumber (Cucumis sativus L.), chili peppers (Capsicum annuum L.), eggplants (Solanum melongena L.), and tomatoes (Lycopersicum esculentum Mill.) were infected with MYMIV, showing symptoms of irregular yellow and mosaic spots on plant leaves. Transmission test exhibited that tobacco plant (Nicotiana tabacum L.) did not show viral infection. PCR detection proved that MYMIV isolates obtained from Yogyakarta may be transmitted through whole seeds, seed coat, cotyledon, and young leaves from sprouting seeds. Mild mosaic symptoms were appeared after sprouting, and gradually vein clearing was observed at 14 days, mosaic at 21 days, and complete leaf yellowing at 45 days after planting.

Identification of a Novel Quinvirus in the Family Betaflexiviridae That Infects Winter Wheat

Yellow mosaic disease in winter wheat is usually attributed to the infection by bymoviruses or furoviruses; however, there is still limited information on whether other viral agents are also associated with this disease. To investigate the wheat viromes associated with yellow mosaic disease, we carried out de novo RNA sequencing (RNA-seq) analyses of symptomatic and asymptomatic wheat-leaf samples obtained from a field in Hokkaido, Japan, in 2018 and 2019. The analyses revealed the infection by a novel betaflexivirus, which tentatively named wheat virus Q (WVQ), together with wheat yellow mosaic virus (WYMV, a bymovirus) and northern cereal mosaic virus (a cytorhabdovirus). Basic local alignment search tool (BLAST) analyses showed that the WVQ strains (of which there are at least three) were related to the members of the genus Foveavirus in the subfamily Quinvirinae (family Betaflexiviridae). In the phylogenetic tree, they form a clade distant from that of the foveaviruses, suggesting that WVQ is a member of a novel genus in the Quinvirinae. Laboratory tests confirmed that WVQ, like WYMV, is potentially transmitted through the soil to wheat plants. WVQ was also found to infect rye plants grown in the same field. Moreover, WVQ-derived small interfering RNAs accumulated in the infected wheat plants, indicating that WVQ infection induces antiviral RNA silencing responses. Given its common coexistence with WYMV, the impact of WVQ infection on yellow mosaic disease in the field warrants detailed investigation.

​RCA-based Detection of Begomoviruses in Weed Ggenera Associated with Legumes in Southern Karnataka

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.

​RCA-based Detection of Begomoviruses in Weed Genera Associated with Legumes in Southern Karnataka

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.

Analysis of the Risk of Profit Loss in Papaya Farming Affected by Yellow Mosaic Disease

Profit loss is a phenomenon caused by the loss of most of the harvest resulting in operating costs greater than the revenue earned. This phenomenon deserves to be analyzed the risk of losses that will be obtained due to pests and plant diseases. So that in this study an analysis of the risk of Profit loss due to yellow mosaic disease on papaya calina was carried out. This research was conducted in October 2020 in Bengkulu Province on 31 Calina Papaya farmers. The location selection was carried out purposively based on the existence of the Calina papaya garden. Meanwhile, the selection of respondents was carried out using the Snowball sampling method in several districts in Bengkulu Province. Data analysis was carried out to determine the Profit loss. Based on the results of the analysis, it was found that there were differences in the benefits of papaya calina which were attacked by the Yellow Virus Mosaic and those that were not attacked by the Yellow Virus Mosaic. Profit loss for a year is Rp 9,135,203,-. This value is a big value, so farmers must handle this disease better.