Survey for the Incidence of Dolichos Mosaic Virus Disease (DMV) in Southern Karnataka

Department of Plant Pathology, College of Agriculture, UAS, GKVK, Bengaluru, Karnataka AICRP on Pigeonpea ZARS, UAS, GKVK Bengaluru, Karnataka

ABSTRACT

Field bean (Lablab purpureusL. Sweet) is one of the important pulse crops in tropics. It’s green beans serve as vegetable. The split or whole dried beans are used as dhal. It is generally considered to have originated in India or South - East Asia. It is commonly called as Dolichos bean, Lablab bean, Hyacinth bean, Indian bean, Bonavista vine, Australian pea, Poor man’s bean, Egyptian bean and locally called as avare in Kannada.The green pods contain a small amount of vitamin A, C, fat, fibre, proteins, iron and rich in calcium. The nutritive quality of dolichos bean is better than that of french bean. The ripe seed contains 20 to 28 per cent protein. Dolichos mosaic virus disease on field bean is caused by a potyvirus is characterised by the symptoms like vein clearing, uneven leaf lamina, twisting of leaves, mosaic mottling and blistering on newly formed trifoliate leaves. The survey was carried out in five districts of Southern Karnataka. The incidence of the disease in the Southern Karnataka ranged from 16.01 per cent to 26.98 per cent. The highest disease incidence was recorded in Ramanagara (26.98 per cent) and lowest disease incidence in Kolar (16.01 per cent) during 2016.

 Keywords Survey, Incidence, Dolichos Mosaic Virus Disease, DMV, Southern Karnataka

Field bean (Lablab purpureus L. Sweet) is one of the important pulse crops in tropics. It’s green beans serve as vegetable. The split or whole dried beans are used as dhal. It is generally considered to have originated in India or South - East Asia. Field bean is commonly called as Dolichos bean, Lablab bean, Hyacinth bean, Indian bean, Bonavista vine, Australian pea, Poor man’s bean, Egyptian bean and locally called as avare in Kannada. It is a multipurpose crop grown for pulse or vegetable for human consumption or as forage for animals (Murphy and Colucci, 1999). In India it is grown in the states of Karnataka, Tamil Nadu, Andhra Pradesh, Kerala and Maharashtra. Karnataka contributes a major share, accounting for nearly 90 per cent in terms of both area and production in the country. Karnataka state records production of about 76,500 tonnes from an area of 85,000 hectares (Anon., 2016). Field bean is susceptible to a variety of diseases caused by fungi, bacteria, viruses and nematodes viz., anthracnose (Colletotrichum lindemuthianum), early blight (Alternaria solani), root and stem rot (Macrophomina phaseoli), bacterial leaf spot (Xanthomonas phaseoli), powdery mildew (Erysiphe polygoni), rust (Uromyces fabae), Dolichos yellow mosaic virus and root knot nematode (Meloidogyne incognita). Among the virus diseases, Dolichos enation mosaic, Leaf roll and Dolichos yellow mosaic virus disease (DYMV) have been reported to occur in India under field condition (Capoor and Verma, 1950). During the kharif of 1990 a severe outbreak of a mosaic disease of field bean was observed in one of the experimental plots of MRS, Hebbal. The incidence of the disease ranged from 25 to 30 per cent. Dolichos mosaic virus disease on field bean was first time reported by Basavaraja and Keshava Murthy (1992) at UAS, GKVK, Bengaluru. The virus was readily sap transmissible and percentage of transmission varied from 46.66 to 100. It is transmitted by two species of aphids viz., Aphis craccivora and Myzus persicae in non-persistent manner. It is also transmitted by Dodder, Cuscuta sp. to a maximum of 40 per cent.

First report of Bean common mosaic virus infecting field bean in India was reported by Udayashankar et al. (2011). The virus belongs to the genus Potyvirus (family Potyviridae). It was designated as Dolichos mosaic virus (DMV) in India and transmitted by aphids in a non-persistent manner and also transmitted by seeds and it causes yield loss up to 40 per cent. The Bean common mosaic virus (BCMV) infected field bean plants showed symptoms of stunting, mosaic, vein banding, vein clearing, mottling, and blisters suggestive of a viral infection infield bean.

MATERIAL AND METHODS

Survey was carried out in five districts of Southern Karnataka namely Bengaluru Urban, Bengaluru Rural, Ramanagara, Kolar, Chikkaballapur during kharif and rabi 2016. To assess the Dolichos

 Table 1. Incidence of DMV disease in field bean growing area of Southern Karnataka during 2016

mosaic virus disease incidence in major field bean growing districts. In each district, 4-5 villages are randomly selected for visual assessment of Dolichos mosaic virus disease incidence. The distance between sampled fields was a few hundred meters to 10 kilometers or more, depending on the availability of field bean fields. In each selected field bean field, virus disease incidence was visually assessed by observations on 50 randomly selected plants. Five points were randomly chosen in each field and observations of virus disease symptoms were made on 10 plants at each point. The plants were scored as either diseased or not, and symptoms were recorded in a field disease survey sheet. The incidence for virus disease symptoms was then computed as the percentage of plants exhibiting symptoms (i.e., by dividing the number of plants with symptoms per field by the total number of plants on which observations were made). Overall disease symptom incidence for each district was calculated by dividing the total number of plants with symptoms by the total number of plants on which observations were made in that particular district In each field, five plots of 10 m2 was selected and the percent of disease incidence was assessed by recording the number of plants showing disease symptoms and the total number of plants examined by using the following formula.

Total number of infected plants Per cent Disease Incidence =———————X 100 Total number of plants observed The observations on stage of the crop infected, varieties grown and symptoms noticed were recorded during survey.

 RESULTS AND DISCUSSION

Dolichos mosaic virus (DMV) disease is one of the important disease occurring in moderate to severe form, which causes great economic loss to the field bean growers. In the present study survey was carried out to assess the Dolichos mosaic virus disease incidence in major field bean growing districts of  Southern Karnataka namely Bengaluru Urban, Bengaluru Rural, Ramanagara, Kolar, Chikkaballapur during kharif and rabi 2016.

Symptomatology

The disease symptoms on infected field bean plants under field conditions consisted of uneven size of leaf lamina, cupping of trifoliate leaves, severe mosaic with dark and light green patches on the leaf, vein clearing and crinkling of leaves with blistering symptoms were observed (Plate. 1 and Plate. 2).

The diagnosis of the disease in the field was based on symptoms on the plants. The symptoms of the dolichos mosaic virus disease observed on infected field bean plants under field conditions included vein clearing, uneven size of leaf lamina, cupping of trifoliate leaves, severe mosaic mottling and puckering of leaves were noticed. The per cent disease incidence was calculated randomly in different locations. The results of the survey conducted during 2016 were presented in Table 1.

The survey was carried out in five districts of Southern Karnataka and one taluk in each district covering 4-5 villages in each taluk. In Bengaluru Rural district, survey was conducted in Hadonahalli, Tubagere, Kavalahalli and Thippuru villages of Doddaballapur taluk. Maximum and minimum disease incidence of 23.88 and 14.40 per cent was recorded in Kavalahalli and Thippuru village respectively. Average DMV disease incidence of 19.85 per cent was recorded in Bengaluru Rural district with range of 14.40 to 23.88 per cent (Table.1).

 In Bengaluru Urban district, survey was carried out in the Bengaluru North taluk. The maximum and minimum disease incidence of 25.95 and 13.99 per cent on HA-4 and HA-3 variety was recorded in ZARS, GKVK, Bengaluru and Rajankunte respectively. Average DMV disease incidence of 21.35 per cent was recorded in Bengaluru Urban district with range of 13.99 to 25.95 per cent (Plate.1).

In Ramanagara district, survey was conducted in the Dandenahalli, Talegere, Chandurayanahalli and Kalya villages of Magadi taluk. Maximum and minimum disease incidence of 28.33 and 25.95 per cent was recorded in Dandenahalli and Chandurayanahalli village respectively. Average DMV disease incidence of 26.98 per cent was recorded in Ramanagara district with range of 25.95 to 28.33 per cent (Plate.2a and b).

 In Kolar district, survey was conducted in the Yalavara, Byalahalli, Kamadenahalli and Chinnapura villages of Kolar taluk. The maximum and minimum disease incidence of 24.07 and 9.89 per cent on local variety was recorded in Yalavara and Chinnapura respectively. Average DMV disease incidence of 16.01 per cent was recorded in Kolar district with range of 9.89 to 24.07 per cent.

In Chikkaballapur district, survey was conducted in the Kuruburu, Yadahalli, Chinnasandra and Hosahalli villages of Chintamani taluk. The maximum and minimum disease incidence of 23.72 and 13.20 per cent on HA-4 and Mani avare variety was recorded in Kuruburu and Chinnasandra village respectively. Average DMV disease incidence of 18.23 per cent was recorded in Chikkaballapur district with range of 13.20 to 23.72 per cent.

Maximum DMV disease incidence was recorded in Ramanagara (26.98 per cent) followed by Bengaluru Urban (21.35 per cent), Bengaluru Rural (19.85 per cent), Chikkaballapur (18.23 per cent) and Kolar (16.01 per cent) in (Table.1 and Fig.1).

Aphids (Aphis craccivora) were invariably found in every infected field surveyed. However, the other insects noticed were includes pod borer, beetles and jassids.

A survey was conducted to assess the Dolichos mosaic virus disease incidence in major field bean growing districts of Southern Karnataka namely Bengaluru Urban, Bengaluru Rural, Ramanagara, Kolar, Chikkaballapur during kharif and rabi 2016.The incidence of the disease in the surveyed fields ranged from 16.01 per cent to 26.98 per cent. The highest disease incidence was recorded in Ramanagara (26.98 per cent) and lowest disease incidence was observed in Kolar (16.01 per cent).The disease symptoms on infected field bean plants under field conditions consisted of uneven leaf lamina, twisting of leaves, vein clearing, mosaic mottling and slight blistering. Similar results were reported by Basavaraja and Keshava Murthy,1992; Shilpashree, 2006; Archith et al.,2017; Naik and Keshavmurthy,1997; Schmidt, 1984; Singh et al., 1976;Makkouket al., 1988.

Maximum dolichos mosaic virus disease incidence was recorded from Ramanagara, Bengaluru Urban and Rural districts as compared to Kolar and Chikkaballapur district. This is probably due to intensive cultivation of field bean in Ramanagara and Bengaluru districts for green pod purpose and provides source of inoculum throughout the year may contribute higher disease incidence compared to Kolar and Chikkaballapur.

 Plate 1. Field view of Dolichos mosaic virus disease on field bean. AVARAD et al., Survey for the Incidence of Dolichos Mosaic Virus Disease (DMV) in Southern Karnataka

 Plate 2. a) DMV affected field bean plot at Dandenahalli village of Ramanagara district

 Plate 2. b) Field view of field bean crop severly affected by DMV at Chandurayanahalli, KVK Farm, Magadi

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