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Department of Plant Pathology, S.V. Agricultural College, ANGRAU, Tirupati-517 502.
The reasons for sudden outbreak of yellow mosaic disease of pigeon pea in isolated patches in Andhra Pradesh during Kharif 2021 was not known. It may be due to association of more than one begomovirus with YMD of pigeon pea or variations in virus or climatic factors or vector biotypes in symptomatology was not known. Roving survey of yellow mosaic disease in pigeon pea was conducted from major growing districts of Andhra Pradesh during December-2022 to January -2023. The symptomology of yellow mosaic disease in redgram was characterized by small yellow diffused spots on the leaves which gradually enlarged to form broad yellow patches. The percent disease incidence ranged from 2-23%. The overall incidence of YMD of Pigeon pea was very low though enough population of whiteflies were observed in the fields and source of inoculums was present on weeds and other pulses grown where the incidence goes upto 100%. Understanding the severity of a disease is crucial for advancing research and gaining valuable insights for further studies..
KEYWORDS: Yellow mosaic disease, begomovirus, survey, percent disease incidence.
The Pigeon pea (Cajanus cajan) is a perennial legume from the Fabaceae family. It is significant drought resistant leguminous food crop, used both for dhal and also for vegetable purpose (Manjunatha et al. 2015). India is the leading country in both redgram production and consumption. Redgram is a staple meal that is high in protein. It has a protein content of roughly 22%, which is nearly three times that of grains. Redgram is ingested as split pulse known as dal, which is a crucial addition to a diet rich in grains (Khairnar et al. 2019). Red gram covers up around 11.8% of the nation’s total pulse area and 17% of its overall pulse production.
India is the world’s major producer of redgram, with 42.8 lakh tonnes grown on 48.24 lakh hectares in 2020– 21 with the yield of 887 kg/hectare on average. Redgram was grown on 2.31 lakh hectares in Andhra Pradesh, yielding 0.83 lakh tonnes (ANGRAU Crop outlook report of Andhra Pradesh 2021). The productivity of pigeon pea can be impacted by different diseases including wilt, pigeon pea sterility mosaic disease, stem blight, stem rot, etc.
Williams et al. (1968) provided the first report of the yellow mosaic disease of pigeon pea’s occurrence. Later Nene et al. (1971) reported based on white fly (Bemisia tabaci) transmission and symptomatology, the mung bean yellow mosaic virus (MYMV) was responsible for the yellow mosaic of pigeon pea. Raj et al., (2005) reported Tomato leaf curl virus with YMD of red gram from Lucknow. Manjunatha et al. (2015) reported association of Horsegram YMV (HgYMV) with pigeon pea YMD in Karnataka based on full length sequence. Severe incidence in isolated patches exhibiting typical bright yellow mosaic symptoms with stunting was observed in redgram fields located at KVK farm, Anantapur. The total DNA was isolated from infected plants, PCR amplified, cloned and sequencing revealed the association of HgYMV with redgram YMD in Andhra Pradesh (Chaitanya et al. 2021). YMD is a severe disease in summer and late rabi seasons that affect pulse crops caused by whitefly transmitted begomoviruses belonging to the Geminiviridae family. Recently new species of begomovirus named as Cajanus scarabaeoides YMV (CsYMV) was reported with wild relative of pigeonpea (C.scarabaeoides) from Chhattisgarh state (Dokka et al., 2023).
The majority of begomoviruses are icosa-hedral twin virion particles with a bipartite genome made up of circular, covalently closed single strand DNA molecules (DNA-A and DNA-B) that are each typically 2.6–2.8kb (Harrison et al. 1977). Symptoms consisting of yellow mosaic, mottling, shortening of leaves and stunting occur in most pigeon pea growing areas at a low incidence.
These begomoviruses have a bipartite genome and contain two single stranded covalently closed circular DNA as their genetic material. These are named as DNA-A and DNA-B, each of approximately 2.7Kb in
size. DNA-A encodes six open reading frames (ORFs), AC1(Replication protein), AC2(Transcriptional activator protein), AC3 (Replication enhancer Protein), AC4(May determine Symptom expression) and AV1(Coat Protein), AV2(Pre coat protein) involved in replication, transcription and packaging, whereas DNA-B encodes two protein ORFs, BC1(movement protein) and BV1(nuclear shuttle protein) involved in viral movement.
Recently high incidence of yellow mosaic and severe stunting of Pigeon pea plants were observed at KVK farm, Reddipalli and other places in Anantapur district during Kharif-2021.The reasons for sudden outbreak of yellow mosaic disease of Pigeon pea in isolated patches in Anantapur district of Andhra Pradesh during Kharif 2021 was not known.
Roving survey was conducted to record the incidence of yellow mosaic disease in major pigeon pea growing areas of Andhra Pradesh during December-2022 to January -2023. The districts covered under this study are Anantapur, Kadapa, Guntur and Prakasam from Andhra Pradesh.
In order to study the symptoms of the disease, healthy plants and yellow mosaic disease infected plants of Pigeon pea are compared during roving survey from different locations. The symptoms exhibited by the diseased plants.
The incidence of the disease was recorded during the survey on naturally infected plants by using following equation as suggested by Wheeler (1969). The zigzag pattern is followed to collect required data in which randomly selected plants were evaluated at each location.
The typical symptoms of YMD observed are mottle mosaic which are small, irregular greenish yellow patches intermixed with green patches. Due to severe infection, there is a stunted in plant growth and reduction in leaf size and internodal length (Fig. 1).
The disease incidence recorded in four districts of Andhra Pradesh is presented in Table 1. The disease incidence in five mandals in Anantapur district ranged from 8-16%, 7-23 % in seven mandals of YSR Kadapa district, 5-6% in two mandals of Prakasam district and 2-8% in four mandals of Guntur district of Andhra Pradesh. The overall incidence of YMD of pigeon pea was very low as compared to YMV on other pulses like urdbean and mungbean where the incidence goes upto 100%. Though enough population of whiteflies were observed in the fields and source of inoculums was present on weeds and other pulses grown at RARS, Tirupati and elsewhere, still the incidence of disease on pigeon pea was very low. It is worth to study the factors like weather, vector, seasons, genotype characters etc., that are responsible for low incidence in several districts surveyed in Andhra Pradesh. Dokka et al. (2023) observed upto 46% disease incidence in Cajanus scaraaeboides- a wild relative of pigeon pea present on bunds of urdbean, munbean and pigeonpea fields in 22 districts of Chattisgarh state during survey carried out from 2017 to 2019.
Based on the above data, it was found that several pigeon pea fields, the plants displayed moderate to low level of incidence showing yellow mosaic symptoms across the fields during survey. The range of disease incidence is observed upto 2-23% in different locations of Andhra Pradesh. The overall incidence of YMD of Pigeon pea was very low as compared to YMV on other pulses like urdbean and mungbean where the incidence goes upto 100%. Though enough population of whiteflies were observed in the fields and source of inoculums was present on weeds and other pulses grown.
Because of this reason, further investigation is need to study the factors like weather, vector, seasons, genotype characters etc., that are responsible for low incidence in several districts surveyed in Andhra Pradesh.
Acharya N.G. Ranga Agricultural University Crop Outlook Reports of Andhra Pradesh REDGRAM (January to December 2021).
Chaithanya, B.H., Reddy, B.B., Prasanthi, L and Devi, R.S.J. 2021. Molecular characterization of virus species causing yellow mosaic disease of redgram in Andhra Pradesh. Ecology, Environment and Conservation. 28(5): 300-305.
Dokka N, Marathe A, Sahu B, Kaushal P, Ghosh PK, Sivalingam PN. 2023. Cajanus Scarabaeoides Yellow Mosaic Virus, a New Bipartite Begomovirus Causing Yellow Mosaic Disease in Cajanus scarabaeoides in India. Plant Disease. 107(10):2924-2928.
Harrison, B.D., Barker, H., Bock, K.R., Guthrie, E.J., Meredith, G and Atkinson, M. 1977. Plant viruses with circular single-stranded DNA. Nature. 270(5639):760-762.
Khairnar, K.Y., Pokharkar, V.G., Yadav, D.B and Kadam, S.A. 2019. Economic impact of red gram production technology on farm productivity and income in western Maharashtra. Journal of Pharmacognosy and Phytochemistry. 8(3):3005- 3009.
Manjunatha, N., Noorulla, H., Anjaneya, R., Archana, S and Manjunath, S.H. 2015. Molecular Detection and Characterization of Virus Causing Yellow Mosaic Disease of Redgram [Cajanus cajan (L.) Millsp] in Karnataka. International Journal of Pure and Applied Bioscience. 3(4):258-264.
Nene, Y.L., Naresh, J.S and Nair, N.G. 1971. Additional hosts of mung bean yellow mosaic virus. Indian phytopathology. 24:415-417.
Raj, S.K., Khan, M.S and Singh, R. 2005. Natural occurrence of a begomovirus on pigeonpea in India. Plant Pathology. 54(6):809.
Wheeler R, B.E.J. 1969. An Introduction to Plant Diseases. John Wiley and Sons Limited, London. 301.
Williams, F.J., Grewal, J.S and Amin, K.S. 1968. Serious and new diseases of pulse crops in India in 1966. Plant Disease Reporter. 52(4):300-304.