This review on Alternaria blight caused by singly or by mixed infection is one of the most widespread and destructive disease of oilseed brassicas in all the continents. These pathogens are necrotrophs. The disease appears as black spot but later on enlarge and develops into prominent round spots with concentric rings. Many spots coalesce to form large patches showing blight and cause defoliation in severe cases. The spots on the mid-ribs of the leaves are linear and sunken. Circular to linear lesions also develop on stem and pods, which elongate at later stages. Infected pods produce small, and shrivelled seeds. This disease causes substantial yield losses as a result of several factors including reduced photosynthetic potential, early defoliation, flower bud abortion, premature ripening, siliquae dehiscence, seed shrivelling and reduced seed size, impairs seed colour and reduced oil content. This paper reviews the research on the development of Alternaria blight, describes the pathogens of Alternaria blight on rapeseed-mustard, which includes geographical distribution, economic importance, symptoms, habitat and host range, pathogen taxonomy, survival, pathogenicity and disease development, epidemiology, host resistance, breeding for disease resistance, genotypic stock, and management.
Field experiments were conducted during 2010-11 to 2011-12 crop seasons to identify resistant genotypes for the management of bacterial blight/black rot caused by Xanthomonas campestris pv. campestris (Pammel) Dawson. Symptoms of disease were recorded 40-45 days after sowing in different localities of Faizabad district of U.P. Disease was characterized by the initial symptoms appeared as dark color streaks on the stem from ground level, which girdle the stem making very soft and hollow followed by rotting. Lower leaves showed midrib cracking 'V' shaped yellowing on the leaf margin, browning of veins and weathering. Profuse exudation of yellowish fluid from the affected stem and leaves may also occur. Out of 110 genotypes screened, ten entries namely T-27, GSL-1, PHR-2, DRMR-243, PBC-9221, JMTA-9, EC-399299, EC-38899, HNS-9605 and HNS-004 were recorded resistant and forty four were moderately resistant. Rest of the genotypes proved moderately susceptible from X. campestris pv. campestris. In absence of resistant genotypes, manage the disease through combination of bio-agents, fungicide and antibiotic such as seed treatment with Pseudomonas fluorescens @ 5g/kg seed + spraying with Streptocycline (100ppm) thrice at 15 days interval followed by Seed treatment with Streptocycline (100ppm) + two sprays with Streptocycline (100ppm) + Copper oxychloride (0.3%) at 15 days interval) , respectively.
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