STUDIES ON MARSSONINA BLOTCH PATHOGENESIS IN APPLE AND ITS MANAGEMENT THROUGH NOVEL METHODS
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Date
2015
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Abstract
ABSTRACT
Marssonina blotch caused by Marssonina coronaria is one of the most important disease of apple
particularly in Himachal Pradesh. Present investigations were undertaken with the objectives to carry out
detailed study on Marssonina blotch pathogenesis in apple, investigate the effect of Marssonina blotch on the
physiological parameters of the host plants and develop novel methods of disease management through induced
resistance. Based on morphological and molecular characters, the isolates collected from different locations of
Himachal Pradesh and Uttarakhand associated with Marssonina blotch of apple were confirmed to be belonging
to Marssonina coronaria. Colonies of all the isolates were dark brown to black without aerial mycelium with
colony diameter ranging from 9 to 14 mm. Conidia were hyaline, ampule shaped, one septate, constricted at the
septum and guttulate, and the conidial size ranged from 3-8×12-28 μm. Molecular characterization of the seven
isolates of Marssonina spp. showed 96-100% homology to with Marssonina coronaria. Phylogenetic tree
depicted that all the isolates were close clustered to Chinese isolates deposited earlier in the NCBI. Pathogenesis
studies revealed highest percentage of conidia germination of Marssonina coronaria on the leaves of Starking
Delicious cultivar and minimum in Granny Smith. Whereas, shortest incubation and latent periods were
recorded in Starking Delicious leaves showing that the cultivar was susceptible to all the isolates tested, while
Tydeman’s Early Worcester showing moderately susceptible and Granny Smith moderately resistant reaction.
Effect of Marssonina coronaria infection on host physiology studies of different apple cultivars revealed that
reducing and non-reducing sugar contents were more in uninoculated leaves of all the test cultivars which
reached maximum with time lapse. Total phenolic content, polyphenol oxidase, peroxidase and PAL activity,
auxins and gibberellins were more in inoculated plants during all the sampling intervals in all the three test
cultivars. Induced resistance studies against Marssonina blotch pathogen on potted plants by using systemic
acquired resistance (SAR) chemicals and bioagents revealed that salicylic acid and acibenzolar-S-methyl @
100 ppm were found to be at par and most effective in all the cultivars tested with minimum disease severity
(1.08 to16.50 %) and maximum disease control (66.77 to 88% ) in the polyhouse.Whereas, among bioagents
tested, Pseudomonas flourescens @ 10-5 dilution was the best with minimum disease severity (1.33 to 18.50 %)
and maximum disease control (61.45 to 83.33 %). To know the mechanism of induced resistance in all the
cultivars tested after treatment with SAR inducers and bioagents, post-inoculation with the pathogen showed
that the biochemical parameters (reducing and non- reducing sugar contents; total phenolic content, peroxidase,
polyphenol oxidase , PAL activity; -l, 3-glucanase and chitinase activity and ROS production) were highest in
salicylic acid treated leaves and minimum in dipotassium phosphate; whereas in bioagent treated leaves they
were recorded in highest levels in case of Pseudomonas flourescens and minimum in Bacillus subtilis. Further,
on comparison among the cultivars, it was found that their contents were higher in resistant Granny Smith
leaves than that in the susceptible cultivar Starking Delicious.
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---, MARSSONINA BLOTCH PATHOGENESIS