Browsing by Author "Netshifhefhe, Nakisani Elelwani Innocentia"

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    Evaluation of maize breeding populations for resistance to Fusarium verticillioides and fumonisin contamination
    (Stellenbosch : Stellenbosch University, 2017-03) Netshifhefhe, Nakisani Elelwani Innocentia; Rose, Lindy J. ; Viljoen, Altus; Flett, B. C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology.
    ENGLISH SUMMARY: Maize is an important crop cultivated all around the world. It is the main source of carbohydrates for over 200 million people in Sub-Saharan Africa. Daily consumption rates can reach up to 500 g per person in certain regions of Africa. Maize production is threatened by several abiotic and biotic factors which include fungi that cause maize ear rots. Fusarium verticillioides, which causes Fusarium ear rot (FER), and Aspergillus flavus, which causes Aspergillus ear rot (AER), are the most common fungal species associated with maize produced in southern and eastern Africa, respectively. Moreover, F. verticillioides produces fumonisins and A. flavus produces aflatoxins which are toxic secondary metabolites associated with harmful effects on humans and animals. Although several management strategies can be used to reduce mycotoxin accumulation in grain, host resistance has been documented to be the most efficient, cost-effective and environmentally sound strategy to minimize contamination. This study focused on evaluating F1 hybrids for improved resistance to FER and fumonisin contamination under South African and Kenyan conditions. A number of hybrids exhibited improved resistance to FER, fungal and fumonisin contamination. In South Africa, hybrids R119W x CKL05015, CML495 x CKL05015 and CKL05015 x R119W were the most resistant to FER severity, F. verticillioides colonisation and fumonisin contamination, respectively. Under Kenyan conditions, fungal colonisation was lowest in hybrids CKL05015 x CML495 and MIRTC5 x CML495, while fumonisin concentrations were lowest in hybrids CML444 x MIRTC5 and R119W x CKL05015. Parental inbred line performance was indicative of F1 hybrids performance. CIMMYT inbred lines CKL05015 and CML495, previously characterised as resistant to AER, exhibited significant resistance to F. verticillioides and its fumonisins across both countries. These lines were also found to be good general combiners for resistance to fumonisin contamination. Furthermore, F2 populations were also evaluated and the resistant F2 populations identified in this study can be used to produce recombinant inbred lines to utilise in genetic fingerprinting and mapping of resistant genes. Significant genotype x environment interactions influenced FER severity, fungal and fumonisin accumulation in maize grain. General combining ability (GCA) and specific combining ability (SCA) were significant for all three infection parameters evaluated while additive gene effects were predominant in the inheritance of resistance in this set of hybrids. This study provided fundamental information on maize lines that could be used by breeders to develop resistant cultivars. Based on the findings of this study, breeding for resistance to F. verticillioides and its fumonisins should be successful and expedited if the parental material involved is resistant.