Abstract
Maize (Zea mays L.) is the most important cereal crop in sub-Saharan Africa providing food for many of its inhabitants. However, production is hampered by low yields and aflatoxin contamination, among others. The toxin contaminates maize before harvest and during storage. Ghana lacks regulatory infrastructure for monitoring and detecting aflatoxin in grains prior to market, and most of the local maize varieties have been found to be susceptible to aflatoxin accumulation. Host resistance is envisaged as a key approach in addressing the aflatoxin menace. Thus, this study was conducted to identify new hybrids that combine high yield with resistance to aflatoxin accumulation as well as study the mode of gene controlling tolerance to aflatoxin accumulation. Sixteen aflatoxin resistant inbreds from exotic sources were crossed as males to 10 local germplasm in a North Carolina II design to generate 160 new hybrids. These were planted together with 9 checks using a 13 × 13 alpha lattice with three replications. The new hybrids were evaluated across six environments in two seasons. Five plants each per hybrid were inoculated with a local strain of Aspergillus flavus at a concentration of 9 × 107conidia/ml. Ninety-six out of the 169 crosses were analyzed statistically. Significant effect of environment and genotypes for all traits especially, for aflatoxin accumulation resistance and yield were observed. The general combining ability effect of males for all traits were found significant (P < 0.05) whereas that of the females were not significant for all traits. Inbreds with consistent significant negative GCA effect for aflatoxin reduction were identified (MP715, TZI8, MP719). Furthermore, the underlying genetic control for the aflatoxin accumulation resistance trait was found to be via both GCA and SCA effects. Heritability estimates were moderate, suggesting permissible transfer of traits during selection to create high yielding aflatoxin resistant hybrids for consumers.
Highlights
The demand for maize continues to increase on the continent of Africa, as it accounts for an average of 32% of calories consumed in Eastern and Southern Africa, and up to 51% in some countries (Cairns et al, 2012)
Maize breeding programmes in Ghana have evolved from an initial use of local landrace varieties to the development of improved Open Pollinated Varieties (OPVs), many of which were bred as Quality Protein Maize (QPM), to the current era of hybrid variety production and promotion
The general combining ability effect of lines used as males for all traits was significant (P < 0.05) whereas those used as females was significant for some of the traits (Table 2)
Summary
The demand for maize continues to increase on the continent of Africa, as it accounts for an average of 32% of calories consumed in Eastern and Southern Africa, and up to 51% in some countries (Cairns et al, 2012). Maize breeding programmes in Ghana have evolved from an initial use of local landrace varieties (which are poor in yield and nutrition) to the development of improved Open Pollinated Varieties (OPVs), many of which were bred as Quality Protein Maize (QPM), to the current era of hybrid variety production and promotion. Current surveys by Perrone et al (2014) on harvested and consumed maize in Ghana revealed the presence of high levels of aflatoxin, well above approved recommended limits of the USA (20 ppb) and that of European Union (4 ppb). Availability of aflatoxin accumulation resistant hybrids will reduce aflatoxin contamination in maize and invariably help address in part the reported cases of serological contamination of over 98% of West African populations who consume contaminated maize and its products (Wild et al, 1990; Jolly et al, 2006; Agbetiameh et al, 2020)
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