Abstract
Aspergillus flavus, causal agent of the Aspergillus ear rot (AER) of maize, also produces aflatoxins that cause aflatoxicosis in humans and livestock. Ten maize inbred lines were evaluated in replicated trials in two aflatoxicosis outbreak hot spots in Kenya and in three maize-growing areas in South Africa for resistance to AER, A. flavus colonization, and pre-harvest aflatoxin accumulation during the 2012/13 growing season. AER severity was measured by visual assessment, while A. flavus colonization and aflatoxin content were quantified by real-time polymerase chain reaction (PCR) and liquid chromatography tandem mass spectrometry, respectively. Genotype by environment interaction (GEI) was determined using analysis of variance (ANOVA), additive main effects and multiplicative models (AMMI), and genotype plus by environment (GGE) biplot analyses. Stability of genotypes was evaluated using AMMI analysis. AER severity and fungal colonization significantly (p < 0.001) varied between genotypes. GEI influenced the severity of AER symptoms and aflatoxin accumulation significantly (p < 0.001), while fungal colonization was not affected. The inbred lines response was consistent for this trait in the test environments and was thus considered a desirable measure to indicate maize lines with a high risk of aflatoxin accumulation. CML495, CKL05019, LaPosta, and MIRTC5 were the least diseased lines, with the lowest aflatoxin contamination and a stable phenotypic response across the environments. Kiboko was determined as the ideal representative test environment, with discriminative ability of the genotypes for selection of the desired stable responses of the three traits.
Highlights
IntroductionAflatoxin is a toxic and carcinogenic compound produced mostly by the fungus Aspergillus flavus
Aflatoxin is a toxic and carcinogenic compound produced mostly by the fungus Aspergillus flavus.Aflatoxins can be found at detrimentally high concentrations in maize grain and other cereals in the tropics due to the prevailing conducive environment for fungal growth and toxin production.Human exposure in Africa is more serious than in other continents because the crops that are highly susceptible to infection by the fungus are the primary staple
Breeding for resistance is still considered to the best strategy currently available to lower aflatoxin accumulation in maize
Summary
Aflatoxin is a toxic and carcinogenic compound produced mostly by the fungus Aspergillus flavus. Human exposure in Africa is more serious than in other continents because the crops that are highly susceptible to infection by the fungus are the primary staple. As the levels that cause regulatory concerns are continually being lowered, it is increasingly difficult for this continent to produce maize that can Agronomy 2017, 7, 86; doi:10.3390/agronomy7040086 www.mdpi.com/journal/agronomy. It is necessary to develop methods that will prevent aflatoxin production in susceptible crops. Breeding of maize varieties for A. flavus resistance is considered an effective and environmentally safe method for controlling contamination, and successful maize cultivars need to be adapted to a range of environments. The objective of this study was to evaluate maize inbred lines for resistance to Aspergillus ear rot (AER), A. flavus colonization, and pre-harvest aflatoxin accumulation under different environmental conditions
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