Oilseed brassicas also known as rapeseed-mustard is an important group of oilseed crop in the world. These crops are susceptible to a number of diseases caused by biotic and mesobiotic pathogens. Among various diseases, Alternaria leaf blight also known as Alternaria dark spot is the most destructive disease of oilseed brassicas species in all the continents. This disease is known to be incited by Alternaria brassicae, Alternaria brassicicola and Alternaria raphani singly or by mixed infection. Alternaria leaf spot pathogens are necrotrophs and produces lesions surrounded by chlorotic areas on leaves, stems and siliquae causing reduction in the photosynthetic areas, defoliation, and early induction of senescence. Alternaria blight causes considerable reduction in quantity and quality of harvested brassica products. The Alternaria leaf blight pathogens are seedborne, soilborne and airborne. The pathogens are greatly influenced by weather with the highest disease incidence reported in wet seasons and in areas with relatively high rainfall. The concentration of conidia, age of the host plants, and wetness period on leaves also influence the severity of the disease. This paper reviews the research and development of Alternaria blight in the oilseed brassicas (rapeseed-mustard) during the past years in relation to pathogen taxonomy, biology, epidemiology, host pathogen interaction and management through chemicals, botanicals, biological, cultural, and biotechnological approaches. The paper also attempts to present future outlook and strategy for Alternaria blight of rapeseed-mustard research.

Alternaria blight disease of mustard caused by a necrotrophic fungus Alternaria brassicae (Berk.) Sacc. is one of the most important limiting factors, causing yield losses of up to 47% in mustard (Brassica juncea). The aim of this present investigation was to evaluate the fungicidal effect of non-conventional chemicals viz. calcium sulphate (CaSO 4 ), potassium chloride (KCl), potassium sulphate (K 2 SO 4 ), zinc sulphate (ZnSO 4 ) and borax (Na 2 B 4 O 7 .10H 2 O) against alternaria blight disease of mustard. The significantly minimum size of spot was recorded in T 1 CaS at 0.5% (1.73) followed by T 3 CaS at 1.5% (1.75) and T 2 CaS at 1.0% (1.78) respectively in comparison to check. The minimum number of average leaf spots/25 mm 2 leaf area was observed in T 3 CaS at 1.5% (1.78) followed by T 1 CaS at 0.5% (2.26). T 1 CaS @ at 0.5% showed significantly lowest disease index (13.00%) followed by T 15 NaB at 0.75% (17.77%) and T 8 KS at 1.0% (18.00%) respectively over check. The average minimum apparent infection rate was recorded in T 1 CaS at 0.5% ( 0.504) followed by T 9 KS at 1.5% (0.553) and T 3 CaS at 1.5% (0.573) respectively. The AUDPC was significantly minimum in all the treatments of CaSO 4 i.e. in T 1 CaS at 0.5% (32.25), T 2 CaS at 1.0% (33.8) and T 3 CaS at 1.5% (35.55) in comparison to check (77.95). The foliar spray of CaSO 4 at 0.5% concentration induced resistance significantly against alternaria blight and reduce pesticide residue in food and environment.

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Oilseed Brassicas are contributing approximately 28 percent of the India’s total oilseed production. This crop is gaining wide acceptance among t he f a rme r s b e ca u s e of adaptability for both irrigated as well as rainfed areas and suitability for sole as well as mixed cropping. Besides, it offers higher return with low cost of production and low water requirement. The production and productivity of oilseed brassicas are comparatively lower as compared to the world average due to the biotic and abiotic constraints. Among the biotic constraints, alternaria blight disease caused by Alternaria spp. has been reported from all the continents of the world, causing up to 70% yield losses in India. This disease was found on leaves, stems and siliquae and dark spots on the leaves and siliquae reduce the photosynthetic capacity and induce immature ripening, which causes reduced amount of quality seed and oil content. The severity of this disease depends upon weather conditions, varieties, age of host plants and virulence of the pathogens. Efforts are being done throughout the world for the management of alternaria blight of rapeseed-mustard. This paper comprehensively reviews the research of alternaria blight of rapeseed-mustard with special reference to management strategies through conventional, non conventional and biotechnological approaches that leads to planning the future research. The present scenario demands the traditional and modern biotechnological techniques bringing together for integrated disease management according to the need and availability at farmers level for sustainable management of alternaria blight disease of oilseed brassicas.

Abstract:The present investigation was done to evaluate the effect of different concentrations of five eco-friendly chemicals in vitro and in vivo, on the management of alternaria blight and yield attributes in Indian mustard (Brassica juncea cv. Varuna). Out of five eco-friendly chemicals, K 2 SO 4 1000 ppm (64.28%) followed by ZnSO 4 1000 ppm (63.88%) showed maximum inhibition of mycelial growth in comparison to check. 0.5% concentration of KCl (57.06%) followed by CaSO 4 (59.50%) and K 2 SO 4 (62.20%) showed significantly maximum effect on spore germination in comparison to check (74.60%). Spore intensity significantly increased by all the treatments except CaSO 4 at 0.5% (40.18%) followed by K 2 SO 4 at 0.5% (29.86%) and ZnSO 4 0.75% (5.11% reduction) in comparison to check. The significantly minimum disease index on leaf over check was found by foliar spray of CaSO 4 at 0.5% (23.58%) followed by CaSO 4 at 1.5% (24.00%) and Na 2 B 4 O 7 .10H 2 O at 1.5% (24.08%). Na 2 B 4 O 7 .10H 2 O at 0.75% showed significantly lowest disease index (23.91%) on pod followed by K 2 SO 4 at 1.5% (25.75%) and KCl at 1.5% (26.00%) in comparison to check. CaSO 4 at 1.0% showed maximum number of primary branches (7.00), number of secondary branches (13.00) and total yield/ha (1917.30 kg/ha) in comparison to check. The results obtained from the present study suggested that K 2 SO 4 showed maximum in vitro effect on Alternaria brassicae and CaSO 4 and Na 2 B 4 O 7 .10H 2 O are providing maximum reduction of disease and increase in seed yield/ha that leads to efficient alternaria blight disease management strategies in field condition. These eco-friendly chemicals can protect the crops from alternaria blight diseases and increase the production and productivity of the Indian mustard crop.