Browsing by Author "Links, Stefan"
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- ItemPhenotypic, physico-chemical and genetic responses of maize associated with resistance to Fusarium verticillioides(Stellenbosch : Stellenbosch University, 2019-04) Links, Stefan; Rose, Lindy; Viljoen, Altus; Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology.ENGLISH ABSTRACT: Maize (Zea mays L.) is integral to the Southern African diet and is a major component of animal feed products. Fusarium verticillioides is an ubiquitous fungal pathogen that contaminates maize grain and is the primary causal organism of Fusarium ear rot (FER) of maize. Grain contamination by F. verticillioides results in two key issues being kernel rot and mycotoxin, specifically fumonisins, contamination. Thus, grain yield and grain quality can be significantly impacted. Ingestion of fumonisin-contaminated grain has been associated with certain health implications in humans and animals such as oesophageal cancer and neural tube defects in humans as well as brain, heart and kidney defects in animals. Cultural and biological management strategies have been explored but despite some advantages for production, these remain inefficient for the management of FER and fumonisin accumulation in maize. Furthermore, there are no registered fungicides available for FER/fumonisin management. Plant resistance offers the most promising approach to managing FER/fumonisins that is both sustainable and environmentally sound. Resistance to F. verticillioides is, however, complex and requires a comprehensive understanding of the mechanisms that contribute to it. Several factors mediate resistance at different levels of infection yet their relative importance and how they correlate to resistance is not well characterised. This study aimed to determine the importance of structural, physico-chemical and genetic traits for resistance. The correlation of these traits with specific infection indicators including FER severity, F. verticillioides growth and fumonisin accumulation in maize grain was also established. Maize inbred lines and commercial cultivars were inoculated with F. verticillioides and different characteristics were analysed. Structural characteristics included silk length, husk coverage, pericarp thickness and kernel hardness. The physico-chemical properties analysed in this study comprised pH, moisture content, total nitrogen and carbon as well as phenolic acids. Finally, reverse transcription quantitative PCR was used to evaluate the genetic response of maize grain to F. verticillioides using pathogenesis-related genes (PR1 and PR5) and as well as peroxidase gene expression. There were significant linear correlations between F. verticillioides growth and fumonisin accumulation in both trials. Significant fungal infection only occurred in one of the two localities (Vaalharts) evaluated. Multifactor analysis revealed no significant relationships between the levels of resistance (structural, physico-chemical and genetic) and infection indicators. However, partial least squares analysis revealed strong associations between individual characteristics and infection indicators. Significant relationships between the genetic response of PR5 and peroxidase genes and infection indicators were determined. Furthermore, significant inverse associations between pH and carbon to nitrogen ratio and infection indicators were found. This study highlighted the importance of physico-chemical and genetic response, in relation to well-established infection indicators commonly used to select resistant genotypes. Furthermore, this study has provided evidence that pH, C/N ratio and the expression of defence-related genes can be, used by breeders, as additional indicators of resistance to FER/fumonisins.