Masters Degrees (Plant Pathology)

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Browsing Masters Degrees (Plant Pathology) by Subject "Agricultural conservation"

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    Monitoring fusarium, gibberella and diplodia ear rots and associated mycotoxins in maize grown under different cropping systems
    (Stellenbosch : Stellenbosch University, 2017-03) Mabuza, Londiwe; Rose, Lindy J. ; Janse van Rensburg, B.; Flett, B. C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology.
    ENGLISH SUMMARY: Maize ear rots represent a significant problem in most maize production areas resulting in reduced yield and quality due to visible fungal infection and mycotoxin contamination of maize grain. Mycotoxigenic fungi affecting cereal grains are particularly important for humans and animals as they pose food safety and security concerns. Increased maize productivity relies on integrated management strategies which include limiting soil erosion and water runoff. Therefore, agricultural practices that involve no-till and the retention of previous crop residues and/or cover crops are steadily increasing in maize production areas in South Africa. The relationship between no-till, the presence of crop residue in the field and maize ear rot disease severity and mycotoxin contamination is not well understood. The increase in the use of cropping systems that support the retention of crop residues in the field could have substantial impacts on maize production and food safety in South Africa. Adequate understanding of the role of agricultural practices in disease outbreaks can assist in enhancing management of maize ear rot pathogens. In this study, the influence of different cropping systems on F. verticillioides and F. graminearum accumulation, Diplodia ear rot (DER) incidence as well as mycotoxin contamination in maize grain was determined. Cropping systems did not significantly affect F. verticillioides accumulation, zearalenone and nivalenol contamination in all the years of evaluation. Fusarium graminearum accumulation, DER incidence and deoxynivalenol contamination were, however, significantly affected in certain years when disease development was favoured. A survey to establish the effect of no-till and conventional tillage practices on Fusarium ear rot, Gibberella ear rot and DER in maize grain and resultant mycotoxin contamination in maize grain was also conducted in commercial farms in South Africa. Additionally, the survival of F. graminearum and F. verticillioides as well fumonisin contamination in crop residue samples collected from conservation and conventional tillage commercial farms in South Africa was also investigated. Tillage practices did not have an effect of fungal accumulation, disease incidence and mycotoxin contamination in maize grain. The results from this study indicate that under local conditions, conservational agricultural practices can be used without the potential risk of enhanced disease accumulation and mycotoxin contamination. Fusarium graminearum and F. verticillioides accumulation and traces of fumonisins were quantified from all analysed crop residues and did not differ between tillage practices. The recovery of these ear rot-causing fungi from crop residues is an indication of its potential to act as inoculum reservoirs for these fungi. Although the levels of fungal target DNA quantified from the crop residues was low, the fungi may reproduce, survive and infect subsequent hosts.