Aflatoxin contamination of maize grain and products causes serious health problems for consumers worldwide, and especially in low- and middle-income countries where monitoring and safety standards are inconsistently implemented. Vitamin A deficiency (VAD) also compromises the health of millions of maize consumers in several regions of the world including large parts of sub-Saharan Africa. We investigated whether provitamin A (proVA) enriched maize can simultaneously contribute to alleviate both of these health concerns. We studied aflatoxin accumulation in grain of 120 maize hybrids formed by crossing 3 Aspergillus flavus resistant and three susceptible lines with 20 orange maize lines with low to high carotenoids concentrations. The hybrids were grown in replicated, artificially-inoculated field trials at five environments. Grain of hybrids with larger concentrations of beta-carotene (BC), beta-cryptoxanthin (BCX) and total proVA had significantly less aflatoxin contamination than hybrids with lower carotenoids concentrations. Aflatoxin contamination had negative genetic correlation with BCX (-0.28, p < 0.01), BC (-0.18, p < 0.05), and proVA (-0.23, p < 0.05). The relative ease of breeding for increased proVA carotenoid concentrations as compared to breeding for aflatoxin resistance in maize suggests using the former as a component of strategies to combat aflatoxin contamination problems for maize. Our findings indicate that proVA enriched maize can be particularly beneficial where the health burdens of exposure to aflatoxin and prevalence of VAD converge with high rates of maize consumption.

Cluster analysis is a type of exploratory analysis that is used for classifying unknown individuals into groups of members that share certain similarity. Grouping breeding materials into different clusters based on their performances under a given condition allows plant breeders to select breeding lines more efficiently. This study aimed to group breeding materials based on their performance under water stress conditions using cluster analysis. The experiment was conducted in RCB design with 3 blocks. Fifty maize inbred lines were grown and exposed to water stress conditions. Twenty-four phenotypic traits were collected and some of them were subjected to cluster analysis. The Partitioning Around Medoid algorithm was used to cluster 50 inbred lines from chosen phenotypes. Cluster validation was then carried out in a subsequent experiment by testing the statistically significant differences between chosen inbred lines and tolerant and susceptible clusters. According to the analysis, 4 clusters with different numbers of inbred lines were obtained. Lines in cluster no. 3 showed the most tolerance compared with the other clusters. In contrast, individuals in cluster no. 1 were the most susceptible. The results of cluster validation in another year also supported this cluster result. Therefore, we concluded that the clustering method was an efficient way to differentiate tolerant and susceptible inbred lines. Furthermore, the results suggested that plant height, tassel size, spikelet density, days to silking, and anthesis-silking interval were secondary traits that could be used in selection for drought tolerance in maize.

Field maize is an important economic crop grown around the world and it has been mainly used in the animal feed industry. Maize yields have been inadequate for the demand due to drought events. One way to alleviate yield losses is to develop drought tolerant maize varieties for farmers. Trehalose-6-phosphate synthase (TPS) is an important enzyme involved in trehalose biosynthesis which has been found to increase plant tolerance to abiotic stresses. The aim of this research was to screen the levels of TPS gene expression in maize breeding materials under water stress via dot-blot hybridization using cDNA probe. To do so, 34 S2 maize families were grown and subjected to water stress condition. Leave samples were collected at 6 different days after planting (DAP) for a dot blot assay. The results showed that the level of TPS gene expression was highest at 4 days after stress (relative intensity at 64 DAP). However, dot blotting at 6 days after stress (relative intensity at 66 DAP) was effective to differentiate maize families. Furthermore, a moderate negative relationship between relative signal intensity at 66 DAP (RI66) and Smith index based on multi-phenotypic traits was found to be statistically significant. Our study showed that maize with high TPS gene expression tended to be less tolerant to water stress. It is noteworthy that the study of TPS gene expression in mature maize under stress in this study showed results that contrasted with previous reports on seedlings in many plant species. Furthermore, we found that 4 out of 34 S2 maize families may have potential for further use in our breeding program.