Abstract
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. Key words: Alternaria blight, rapeseed-mustard, symptoms, variability, pathogen, survival, management.
Highlights
Oilseed brassicas often called rapeseed-mustard is the third most important oilseed commodity in the world after soybean (Glycine max) and palm (Elaeis guineensisJacq.) in world agriculture and India is the third largest producer with global contribution of 28.3% acreage and19.8% production (Shekhawat et al, 2012; Bandopadhyay et al, 2013)
Alternaria blight causes substantial yield losses as a result of several factors including reduced photosynthetic potential, early defoliation, flower-bud abortion, premature ripening, siliquae dehiscence, seed shriveling (Seidle et al, 1995), and reduced seed size and impairs seed color and oil content (Kaushik et al, 1984).This review describes the pathogens of Alternaria blight of oilseed brassicas, epidemiology, host pathogen interaction and management through various approaches
The fungus can survive in susceptible weeds or perennial crops (Chupp and Sherf, 1960; Rangel, 1945; Maude and Humpherson-Jones, 1980a, b) and these weed host plants help the Alternaria blight pathogen to propagate the infective entities which serve as the source of inoculum for the oilseed Brassicas
Summary
Oilseed brassicas often called rapeseed-mustard is the third most important oilseed commodity in the world after soybean (Glycine max) and palm The ideal weather condition required for adhesion, germination, penetration and establishment of pathogen in host plays a major role in the development of disease Other factors such as density of airborne conidia (Humpherson-Jones and Ainsworth, 1982), plant age (Awasthi and Kolte, 1994), temperature, humidity and wetness period (Hong and Fitt, 1995) are reported to influence the severity of Alternaria leaf blight. The fungus can survive in susceptible weeds or perennial crops (Chupp and Sherf, 1960; Rangel, 1945; Maude and Humpherson-Jones, 1980a, b) and these weed host plants help the Alternaria blight pathogen to propagate the infective entities which serve as the source of inoculum for the oilseed Brassicas. Foliar sprays of aqueous bulb extract of Allium sativum (garlic) and Eucalyptus globulus (Eucalyptus) have been reported to effectively manage the Alternaria blight on leaves and
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