Present status of Soybean yellow mosaic virus in agro-climatic zones of Marathwada region of the Maharashtra state

Introduction

Soybean (Glycine max (L.) Merrill; 2n=40) is recognized globally as one of the most important oilseed and protein-rich legume crops. Its origin and early domestication trace back to ancient China, where it was cultivated as a sacred grain, as documented in the earliest Chinese pharmacopeia, "Pen Ts'ao Kang Mu", compiled in 2838 B.C. by Emperor Shen Nung (Hymowitz, 1970) [7] . Over time, soybean spread beyond East Asia, reaching Europe in 1712, the United States in 1804, Brazil in 1903, and East Africa by 1907, eventually making its way to India between 1870 and 1880 (Mali & Thottappilly, 1989) [12] . Significant advancements in soybean improvement occurred during the 1940s and 1950s in the United States, where systematic breeding programs transformed the plant from a relatively inefficient fodder crop into a high-yielding erect type, establishing the U.S. as the world's leading soybean producer (Hymowitz & Harlan, 1983) [8] . From a taxonomic perspective, Linnaeus first described the crop under different genera before Merrill (1917) [13] proposed the currently accepted name Glycine max (Ratnaparkhe et al., 2011) [18] . The genus Glycine falls under the family Leguminosae and includes two subgenera: Glycine (wild perennial species) and Soja (annual species), the latter comprising the cultivated soybean and its wild progenitor Glycine soja. Soybean is often referred to as the "golden bean" owing to its rich nutritional composition approximately 38-43% protein and about 20% oil along with a favourable amino acid profile, including high levels of lysine, which enhances its biological value as a plant-based protein source (Kudełka et al., 2021) [10] . Historically, soybean has been deeply embedded in East Asian food culture, where it is consumed in diverse forms such as miso, shoyu, tofu, soymilk and tempeh, contributing significantly to regional nutritional security (Rizzo & Baroni, 2018 [19] ; do Prado et al., 2022) [3] . Globally, soybean is cultivated across major agro-ecological zones. India remains one of the key producers, ranking fifth worldwide with approximately 10 million metric tons (MMT) of production (SOPA, 2020). During 2019-20, India harvested nearly 12 million hectares of soybean, producing 9.30 MMT with an average productivity of 0.78 MT/ha (USDA, 2020). In Maharashtra one of the major soybeangrowing states the crop occupied 37.37 lakh hectares during the 2019 Kharif season, yielding 39.42 lakh metric tons (SOPA Databank, 2019). Despite its economic importance, soybean productivity in India has remained comparatively low due to several interlinked constraints. Over 90% of the crop is cultivated under rainfed conditions, exposing it to periodic drought stress, plant mortality and significant yield losses (Holt et al., 1997) [6] . Additionally, biotic stresses, including fungal, bacterial, viral and nematode diseases, further limit production (Paroda, 1999 [16] ; Joshi & Bhatia, 2003) [9] . Globally, more than 60 viruses are known to infect soybean, among which 27 are considered economically important. Notable viral pathogens include Soybean mosaic virus, Cowpea mild mottle virus, Tobacco ringspot virus, Mungbean yellow mosaic virus, Alfalfa mosaic virus, and Cucumber mosaic virus. Soybean yellow mosaic virus (SYMV), a member of the potyvirus group belonging to the Bean common mosaic virus lineage, has emerged as one of the significant threats across South and East Asia (Gibbs et al., 2008) [4] . SYMV was first reported in the United States in 1953 (Pierce, 1953) [17] and subsequently identified in India in 1960 (Nariani, 1960) [14] . It is now widespread across northern and central Indian states, including Madhya Pradesh, Punjab, Haryana, and Karnataka (Bhattacharyya et al., 1999) [1] . The disease is characterized initially by small chlorotic spots that progress into yellow mosaic patches, ultimately leading to complete leaf yellowing. Infected plants bear fewer pods, resulting in yield reductions ranging from 30% to 70%, and in severe epidemics, losses may reach 80% (Malathi, 2007 [11] ; Nene, 1972) [15] . In recent years, SYMV has gained prominence in the Marathwada region of Maharashtra, where soybean constitutes a major Kharif crop. Given the expanding incidence, wide host range and increasing severity of the virus, region-specific surveillance has become essential. Systematic field surveys provide critical insights into disease prevalence, hotspot identification and spatial distribution, thereby supporting timely and effective plant protection interventions. Considering these challenges, the present study was undertaken to assess the current status and incidence of SYMV across different agro-climatic zones of the Marathwada region, with the aim of generating baseline data crucial for disease management and future research.

Materials and Methods

Survey

A random survey of selected soybean crop fields, covering three Agro-climatic zones viz., Scarcity Zone (SZ), Assured Rainfall Zone (ARZ) and Moderate Rainfall Zone (MRZ) of Marathwada region of the Maharashtra state were undertaken during Kharif, 2023-24 and 2024-25, to assess soybean yellow mosaic virus incidence and simultaneously collected the disease samples in paper bags and well labeled. Soybean growing pockets / fields were identified from the records available at the office of Sub-Divisional Agriculture Officers, of the respective districts. In the selected soybean crop fields, a 10 m 2 area was randomly selected and counted total number of soybean plants and number of plants showing typical soybean yellow mosaic virus symptoms were recorded and per cent disease incidence were calculated, by applying following formula,

Results and Discussion Occurrence and distribution of soybean yellow mosaic virus disease

A random survey to record yellow mosaic virus disease in soybean incidence and severity was conducted during the Kharif, 2023-24 and 2024-25 covering 157 and 182 soybean crop fields of 08 districts, distributed under three agroclimatic zones viz., Scarcity zone (06), Assured Rainfall zone (07) and Moderate rainfall zone (08) of Marathwada region of the Maharashtra state (Figure 1 and Plate 1A to 1E). The results obtained soybean yellow mosaic virus disease, tahsil-wise (Table 1), district-wise (Table 2), soybean verities wise (Table 3) and agro-climatic zone-wise (Table 4) are being interpreted herein under following sub-heads.

Tahsil-wise yellow mosaic virus disease in soybean

The results (Table 1) indicated a wide range of yellow mosaic virus disease in soybean incidence during both the years of survey. Disease incidence was ranged from 14.56 (Wadavani) to 51.13 (Chatrapati sambhajinagar) and 22.23 (Wadavani) to 62.96 (Chatrapati sambhajinagar) per cent, during Kharif, 2023-24 and 2024-25, respectively. However, maximum yellow mosaic virus disease in soybean incidence was recorded in Chatrapati sambhajinagar tahsil (51. 13

District-wise yellow mosaic virus disease in soybean incidence

Results (Table 2) revealed maximum yellow mosaic virus disease in soybean incidence 40.98% and 45.82% in Chatrapati sambhajinagar district, respectively, during Kharif 2023-24 and 2024-25, with maximum pooled incidence of 43.40%. This was followed by the districts of viz., Parbhani (34.12%, 40.08% and 37.10%), Jalna (31.97%, 40.05% and 36.01%), and Nanded (32.30%, 36.99% and 34.64%) Hingoli (31.04%, 37.17% and 34.09%), Osmanabad (30.41%, 35.30% and 32.85%), Beed (30.00%, 33.07% and 31.43%) and Latur (25.10%, 32.87% and 29.08%). Overall average yellow mosaic virus disease in soybean incidence was maximum (37.66%) during Kharif, 2024-25 and was comparatively minimum (31.99%) during Kharif, 2023-24.

Variety wise yellow mosaic virus disease in soybean incidence

Result (Table 3) indicated that among overall 12 soybean varieties grown by the farmers of the Marathwada region surveyed (Kharif, 2023-24 and 2024-25), maximum yellow mosaic virus disease in soybean incidence was found in KDS (26.84 and 33.30%), respectively. during Kharif, 2023-24 and 2024-25, with pooled mean maximum incidence 30.07%. This was followed by varieties viz. MAUS-725 (27.10%, 30.52% and 28.81%), MAUS-725 (20.16%, 26.18% and 23.17%), JS-97-52 (20.20%, 24.80% and22.50%), KDS-992 (19.16%, 25.38% and 22.27%), TDS-753(19.20%, 22.33% and 21.76%). In rest of the varieties of soybean, the yellow mosaic virus disease in soybean incidence ranged from 12.34% to 18.08% and 15.84% to 19.70%, respectively during Kharif, 2023-24 and 2024-25, with pooled mean incidence in the range of 14.28% to 18.89%.

Agro-climatic zone-wise yellow mosaic virus disease in soybean incidence during Kharif, 2023-24 and 2024-25

Results (Table 4) revealed that among three agro-climatic zones viz., Scarcity zone (SZ), Assured rainfall zone (ARZ) and Moderate rainfall zone (MRZ) surveyed, maximum yellow mosaic virus disease in soybean incidence of 33.35 and 37.51 per cent, respectively during Kharif, 2023-24 and 2024-25, with maximum pooled mean incidence of 35.43 percent in Moderate zone, followed by Assured rainfall zone (32.45%, 36.22% and 34.33%) and Scarcity zone (27.08%, 34.94% and 31.01%). Overall average yellow mosaic virus disease in soybean incidence was maximum (36.22%) during Kharif, 2024-25 and was comparatively minimum (30.96%) during Kharif, 2022-23. Similar findings were observed by Bhugabati and Goswami (1992) [2] recorded that in bhendi crops sown during May and June, the yellow mosaic disease was found to be highest (100 percent). The disease incidence and whitefly population, however, were found to be the lowest in crops sown in the month of October. Singh et al. (1998) [20] surveyed the field of 20 villages of Madhya Pradesh, India and reported the incidence of yellow mosaic virus, whitefly (Bemisia tabaci) in soybean. Green (1999) [5] reported under survey statement (by AVRDC) that to reveal the natural occurrence of Mungbean disease caused by Gemini viruses, they collected samples of Mungbean (24 variety samples) from Bangladesh, black gram (30 samples), soybean (2 samples) from western India, Mungbean (14 samples) from Sri Lanka and not a single sample of Mungbean from Tanzania, India Thailand and Vietnam were positive for Mungbean yellow mosaic virus (MYMV) detected with nucleic acid hybridization and PCR.

Acknowledgement

AcknowledgmentThe authors are grateful to Department of Plant Pathology, College of Agriculture, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani for providing facilities to conduct this research and survey. The authors are also grateful to all those who helped for providing useful information during survey.

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