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Meena P.D.,National Research Center on Rapeseed Mustard | Chattopadhyay C.,National Research Center on Rapeseed Mustard | Meena S.S.,National Research Center on Rapeseed Mustard | Kumar A.,National Research Center on Rapeseed Mustard
Archives of Phytopathology and Plant Protection | Year: 2011

Plant age has a major influence on the incidence of Alternaria blight disease in Indian mustard crops. Disease progression was monitored twice a week on the two chosen Indian mustard cultivars viz., Varuna and Rohini throughout the season. Severity of blight caused by Alternaria brassicae and Alternaria brassicicola decreased with delay in sowing. Calculation for A-value (Area under disease progress curve - AUDPC) and r-value (apparent infection rate) in crops sown on different dates could identify the speed of progress in the disease on leaves and pods, as the crop does not posses resistance to the pathogen till date. Thus, the probable dates of sowing enabling slow disease progress or the weather conditions coinciding with the different crop phenological stages demarcated the advantageous dates of sowing from the disadvantageous ones. However, cultivar Varuna is more susceptible as compared to the other cultivar Rohini, as apparent infection rate both on leaves and pods was higher in former. Highest per cent disease severity (PDS) for season highly correlated with date of sowing, i.e. delayed date of sowing increased PDS. © 2011 Taylor & Francis.

Chattopadhyay C.,National Research Center on Rapeseed Mustard | Agrawal R.,Indian Agricultural Research Institute | Kumar A.,Indian Agricultural Research Institute | Meena R.L.,National Research Center on Rapeseed Mustard | And 6 more authors.
Archives of Phytopathology and Plant Protection | Year: 2011

Experiments were laid out at Bharatpur, New Delhi and Kangra with Indian mustard (Brassica juncea) cvs 'Varuna' and an important one in the locality sown on 10 dates at weekly intervals. First appearance of white rust disease (Albugo candida) on leaves and pods (staghead formation) of mustard occurred between 36 and 131 days after sowing (d.a.s.), 60 and 123 d.a.s., respectively. Severity of white rust disease on leaves was favoured by > 40% afternoon (minimum) relative humidity (RH), > 97% morning (maximum) RH and 16-24°C maximum daily temperature. Staghead formation was significantly and positively influenced by 20-29°C maximum daily temperature and further aided by 4128C minimum daily temperature and 497% morning (maximum) RH. Regional and cultivar specific models devised could predict, at a few weeks after sowing, the crop age at which white rust first appeared on the leaves, as staghead, the highest rust severity on leaves, staghead numbers and the crop age at peak rust severity on leaf, highest staghead numbers at least 1 week ahead of first appearance of the disease on the crop. © 2011 Taylor & Francis.

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