CHARACTERIZATION OF PATHOGENS ASSOCIATED WITH RHIZOME ROT OF GINGER (Zingiber officinale Rosc.) AND DECIPHERING HOST RESISTANCE
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Date
2021-01-29
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bagalkot).
Abstract
The present study was conducted to characterize the pathogens involved in the
causation of rhizome rot of ginger and to decipher the resistance mechanism. The study
revealed that rhizome rot of ginger is a complex disease caused by the interaction of
different pathogens. Isolation of pathogens collected from major ginger growing areas
of Karnataka and Kerala revealed the association of pathogens viz; Pythium
aphanidermatum, Fusarium oxysporum, Fusarium solani, Sclerotium rolfsii, Ralstonia
solanacearum, Meloidogyne hapla and Meloidogyne enterolobii in causing rhizome
rot of ginger. Pathogenicity of the individual causal organisms was proved by using
Koch postulates. Molecular characterization and species level identification of fungi and
bacteria was carried out by using species specific primers. Sequencing of the nematode
DNA revealed higher similarity with Meloidogyne hapla and Meloidogyne
enterolobii.
All the pathogens can cause potential disease as individuals and in combinations
at different plant growth stages tested viz; 75 DAP, 105 DAP and 135 DAP. At 135
days after planting plants recorded higher per cent disease incidence and rhizome rot
incidence. Combination of P.aphanidermatum, Fusarium spp., Sclerotium rolfsii,
Ralstonia solanacearum , Meloidogyne spp. recorded higher per cent disease incidence
and rhizome rot incidence in all the intervals. The maximum disease incidence was seen
in sequential inoculation of Meloidogyne spp. followed by R. solanacearum.
None of the elicitors except biocontrol agents found effective during in vitro
evaluation. External application of elicitors resulted in higher expression of defense
genes such as ERF transcdription factor, HMGR, HMGS, HSP, ABC, MLO, WRKY,
Callose synthase, Glucanase and PR-5. All the genes were expressed in higher fold as
compared with zero hours. External application of methyl jasmonate as prophylactic
manner resulted in reduced per cent disease incidence and rhizome rot as compared to
curative treatments.
Screening of varieties under different conditions revealed that none of the
varieties showed resistance against the pathogens. Among two different nanoparticles
used against the pathogens, copper nanoparticles were found more effective against the
disease complex.
Antibiotics and fungicides were evaluated under in vitro conditions and the best
molecules were evaluated under field conditions during 2018-19 and 2019-20. An IDM
module was developed considering all the effective molecules and the treatment having
soil application of carbofuran (25 kg /ha), rhizome treatment with COC (3g/L) and
streptocycline (0.5 g/L) for 30 min, foliar application methyl jasmonate (200 ppm),
drenching with fosetyl (2g/L) followed by drenching with sectin (2g/L) was found most
effective in reducing the disease and rhizome rot with highest yield /ha with maximum
B: C.
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