Induction of resistance for the management of Alternaria leaf spot of cauliflower
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Date
2020-10-18
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COLLEGE OF HORTICULTURE AND FORESTRY, DR Y S P UHF, NERI, HAMIRPUR
Abstract
The pathogen causing Alternaria leaf spot of cauliflower was isolated and identified as
Alternaria brassicicola on the basis of morphological characters and sequencing of DNA region
coding for internal transcribed spacer (ITS) region. Amplification of genomic DNA of fungus with
primer pair ITS1 and ITS 4 gave a single band of approximately 500 bp on gel electrophoresis. In
pathogenicity test, 72 hours of incubation period of A. brassicicola was observed by spray inoculation
of the pathogen. Among eight different abiotic resistance inducers, foliar sprays of salicylic acid (20
mM) and potassium chloride (100 mM) was found most effective for the management of Alternaria
leaf spot of cauliflower in pot and field experiment. Under field conditions, three foliar sprays of
salicylic acid (20 mM) and potassium chloride (100mM) resulted in reduction in disease incidence up
to 76.81 and 71.01 per cent and disease index up to 78.69 and 73.36 per cent, respectively with
maximum curd yield of 2.68 and 2.37 kg/plot. The phenol content and activity of polyphenol oxidase
and peroxidase was maximum after three days of pathogen inoculation which then gradually diluted
with time. Among aqueous extracts, maximum mycelial inhibition of 65.47 per cent was observed by
using extract of Phyllanthus emblica at 50 per cent concentration. Cow urine alone resulted in
complete inhibition in mycelial growth of pathogen at different tested concentrations i.e 10, 15 and 20
per cent. While, in cow urine based extracts, maximum mycelial inhibition of 53.33 and 51.67 per
cent was observed by using extract of Ocimum tenuiflorum and Phyllanthus emblica at 20 per cent
concentration. In dual culture assay, under in vitro conditions, Trichoderma harzianum I-6 strain
resulted in maximum mycelial inhibition of 80.64 per cent followed by T. viride (78.49 %). Root dip
treatment of cauliflower seedlings with T. harzianum I-6 strain was also found most effective with
reduction of 32.70 and 40.00 per cent disease incidence and per cent disease index, respectively