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Salicylic acid suppression of clubroot in broccoli (Brassicae oleracea var. italica) caused by the obligate biotroph Plasmodiophora brassicae

journal contribution
posted on 2013-01-01, 00:00 authored by David Lovelock, C Donald, Xavier ConlanXavier Conlan, David CahillDavid Cahill
The obligate soil-borne biotroph Plasmodiophora brassicae has a significant economic impact on Brassicaceae crops. The pathogen severely disrupts the roots by inducing the production of galls which leads to malformation and reduced growth of the roots and a reduced ability to take up water and nutrients. Control of P. brassicae is difficult because it has a number of survival and dissemination strategies that involve both motile and resting stages that need to be targeted by any control agent. We investigated, under controlled conditions and in glasshouse and field experiments, the potential of salicylic acid (SA), a key phytohormone, that is required for defence against certain biotic and abiotic stresses, to reduce infection by P. brassicae in broccoli (Brassicae oleracea var. italica). Under controlled conditions in a growth cabinet exogenous application of SA to roots resulted in its transport systemically to the leaves where it promoted the up-regulation of the pathogenesis related genes PR-1 and PR-2 in an SAR-like response as early as 24 h post-treatment. Concentrations of SA >20 mM reduced significantly both shoot and root weights when applied exogenously but lower concentrations had little measureable effect on plant growth. When SA was applied to plants above 5 mM there was a significant reduction (25-65 %) in gall formation 6 weeks post-inoculation with P. brassicae, indicating that the pathogen was being controlled by the addition of SA. A combination of SA and JA was also shown to reduce severity (25-35 %) of disease associated with P. brassicae. These findings indicate that there may be SA inducible mechanisms in B. oleracea that if fine-tuned could provide enhanced resistance to clubroot disease.

History

Journal

Australasian plant pathology

Volume

42

Issue

2

Pagination

141 - 153

Publisher

Springer Netherlands

Location

Amsterdam, The Netherlands

ISSN

0815-3191

eISSN

1448-6032

Language

eng

Publication classification

C1 Refereed article in a scholarly journal