Epidemiology, management and induction of systemic resistance against Alternaria blight of Indian mustard incited by Alternaria brassicae (Berk.) Sacc.
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Date
2018
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CCSHAU
Abstract
Alternaria blight disease incited by A. brassicae is one of the most widespread and destructive fungal disease
of rapeseed-mustard throughout the world. In Haryana state the Alternaria disease appears every year in severe form at
pod initiation stage in Indian mustard (Brassica juncea) that affects the seed germination as well as quality and quantity
of oil. Keeping in view the enormous loss caused by the pathogen, the present investigation has been devised on
epidemiology, management and induction of systemic resistance studies under laboratory, screen house and field
conditions during rabi 2015-16 and 2016-17 at Chaudhary Charan Singh Haryana Agricultural University, Hisar. In
epidemiological studies the two Indian mustard varieties namely RH 30 and RH 0749 were sown in different dates to
observe the effect of weather factors on onset and progression of disease. In the initial two dates of observations, the
disease progression was slow and non-significant among different date of observations in first two dates of sowing;
however, after first week of February significant differences in disease severity was observed in all dates of sowing
except for 9th November sown crop, where the disease progression was significantly differed after second week of
February. Among all dates of sowing, maximum disease severity was recorded in late sown crop i.e. 9th November, while
minimum disease severity was recorded in timely sown crop i.e. 20th October on both varieties. Hence, it is clear from the
present investigation that the disease severity increased with delay of sowing. The progression of disease on two cultivars
indicated that Alternaria blight progression was rapid and more severe on cultivar RH 30 in different dates of sowing as
compared to cultivar RH 0749. The foliar spray with mancozeb at 45 DAS followed by hexaconazole at 60 DAS was
found most effective in controlling Alternaria leaf blight severity (78.0 %) and Alternaria pod blight severity (56.5%)
with increased seed yield (29.9%) as compared to untreated control. One thousand genotypes of diverse origin
(indigenous and exotic) were screened for their relative resistance to Alternaria blight disease under artificial inoculation
conditions in field. Out of these, sixty four germplasm lines showed moderately resistance reaction (≤10% disease
severity) against Alternaria leaf blight. It was note worthy that out of sixty four moderately resistant germplasm lines;
twenty six germplasm lines were found to be matured early which might have escaped the high infection as the weather
conditions were not favourable at that period of time. Reasonably, remaining thirty eight genotyped were considered for
having moderate resistance to this pathogen in Indian mustard. None of the chemical completely inhibited the mycelial
growth even at higher concentration of 150μg/ml. However, a maximum inhibition of mycelial growth (49.2%) was
recorded by salicylic acid at 150μg/ml concentration as compared to inhibition of 21.4 per cent at 10μg/ml concentration
followed by indole acetic acid which inhibited the fungal growth up to 41.7 and 13.6 per cent at 150μg/ml and 10μg/ml
concentration, respectively. A maximum control was also recorded by salicylic acid at 100μg/ml concentration after six
weeks of challenge inoculation by the pathogen followed by indole acetic acid in both the cultivars under screen house
conditions. SA has shown maximum induction of total phenol content, PO, PPO, PAL and chitinase activity at three days
after inoculation (DAI) in both the cultivars at 100μg/ml concentration followed by IAA. However, ZnSO4 has shown
minimum induction of these activities at three DAI in both the varieties.
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