Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance
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Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Agricultural Science
Abstract
Black Sigatoka is a major disease of East African highland cooking bananas in Uganda. Aqueous extracts of
Azadirachta indica, Cinnamomum zeylanicum and Capsicum annuum have shown the potential to reduce Black
Sigatoka in banana plantlets. The mechanisms by which plant extracts confer protection against plant pathogens
has previously been reported to involve activation of defence and direct antimicrobial activity. In the current
study, both antimicrobial activities of selected extracts were studied as well as expression of three
defence-related genes using quantitative real-time PCR. Gene expression was compared in susceptible (cv.
Musakala, genomic group AAA-EA) and resistant (cv. Kayinja, genomic group ABB) banana cultivars.
Additionally, Musakala treated with A indica extract at 1 day before inoculation (DBI) was tested for induction
of defence-related genes at 0, 10 and 20 days after inoculation (DAI). Pathogenesis-related genes (PR-1 and
PR-3) and non-expressor of PR-genes (NPR1B) were up-regulated in the resistant cultivar. The genes analysed
responded at late time points to M. fijiensis inoculation in both extract-treated and control plants in the
susceptible cv. Musakala. On the other hand, A. indica and C. annuum completely inhibited mycelial growth of
M. fijiensis at 30% (w/v). These findings suggest that the effect of plant extracts on Black Sigatoka is strongly
associated with the direct antimicrobial effects.
Description
Keywords
Banana, Plant extracts, Black Sigatoka, Defence genes
Citation
Kumakech, A., Jorgensen, HJL, Collinge, DB, Edema, R., & Okron, P. (2017). Azadirachta indica reduces Black Sigatoka in East African highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance. Journal of Agricultural Science , 9 (4), 61-76. DOI: 10.5539/jas.v9n4p61