Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance

TY - JOUR

T1 - Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance

AU - Kumakech, Alfred

AU - Jørgensen, Hans Jørgen Lyngs

AU - Collinge, David B.

AU - Edema, Richard

AU - Okori, Patrick

PY - 2017

Y1 - 2017

N2 - 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.

AB - 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.

U2 - 10.5539/jas.v9n4p61

DO - 10.5539/jas.v9n4p61

M3 - Journal article

SN - 1916-9752

VL - 9

SP - 61

EP - 76

JO - Journal of Agricultural Science

JF - Journal of Agricultural Science

IS - 4

ER -