Although drought intensity increases aflatoxin contamination, drought tolerance does not lead to less aflatoxin contamination

V Vadez,F Waliyar,A Rathore,F Hamidou

doi:10.1016/j.fcr.2013.10.019

Abstract

Drought stress is known to increase aflatoxin contamination in groundnut and establishing a possible relationship between drought tolerance and resistance to aflatoxin contamination could contribute to a more efficient selection of aflatoxin-resistant genotypes. In recent work, the reference collection of groundnut had been assessed across seasons varying for drought intensity, i.e. two moderate temperature (rainy season) and two high temperature (dry season) experiments under well-watered (WW) and water stress (WS) conditions (Hamidou et al., 2012, 2013). Here aflatoxin concentration (AC) in seeds is measured in these trials, first for possibly identifying germplasm with low aflatoxin concentrations and second for investigating possible relationships between aflatoxin concentration and drought tolerance. Drought stress intensity increased aflatoxin concentration in seeds and higher aflatoxin contamination was observed under combined drought and high temperature conditions than under drought alone. No germplasm with lower AC than resistant check (55-437) were found. Aflatoxin contamination showed very high GxE interactions, which suggest that selection for resistance to aflatoxin contamination must be specific to environment. Across trials, using means for each environment, there was a clear positive relationship between the aflatoxin concentration and the grain yield reduction due to drought, indicating that a higher drought severity led to higher aflatoxin concentration. However, within trial, the same relationships applied to individual genotypes, or to cohorts of tolerant/sensitive genotypes, were not significant. The major conclusion of this work is that while drought intensity did increase the level of aflatoxin contamination, as expected and previously reported, there seemed to be no direct relationship between tolerance to drought and aflatoxin concentration, suggesting that the mechanisms of drought tolerance and aflatoxin contamination are likely not common.

Highlights

Aflatoxin, a toxin produced by fungi Aspergillus flavus (A. flavus), is acutely toxic to some animals and carcinogenic to humans (Thirumala-Devi et al, 2002)
Aflatoxin contamination increases under drought stress (Girdthai et al, 2010a) because of decrease in the water activity, that creates cracks in pod wall that allow the penetration of the A. flavus
In a previous paper (Hamidou et al, 2013), we found that intermittent drought under field conditions had milder effects on yield under moderate temperature conditions than when a similar drought stress was imposed under higher temperature conditions

Summary

Introduction

A toxin produced by fungi Aspergillus flavus (A. flavus), is acutely toxic to some animals and carcinogenic to humans (Thirumala-Devi et al, 2002). High level of aflatoxin content in groundnut-derived products for consumption is one of the main problems related to groundnut commercialization. Breeding groundnut for aflatoxin contamination resistance would have. A broad impact on groundnut kernel quality, thereby enhancing the economic return and well-being of small-holder farmers, and health of consumers. The fungi penetrate into the pods through small cracks that develop during pod maturation and drying (Robert et al, 1971; Sanders et al, 1984). Aflatoxin contamination increases under drought stress (Girdthai et al, 2010a) because of decrease in the water activity, that creates cracks in pod wall that allow the penetration of the A. flavus. Groundnut genotypes which maintained high kernel moisture showed enhanced resistance and produced low aflatoxin (Cole et al, 1993). Other findings demonstrated that decrease of kernel water activity reduced phytoalexin

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