Suchergebnisse

Genetic improvement is an emerging method to reduce the levels of fumonisin (FB) contamination in maize, but breeding advances depend on the development of suitable methods to accurately assess the performance of different cultivars. Our study focused on characterizing a local isolate of Fusarium verticillioides; comparing artificial inoculation techniques with this isolate (injection into kernels and down the silk channel); and assessing white maize resistance under artificial vs. natural inoculation. The fungal growth rate significantly increased with temperature and water activity a w. The optimum growth rate, corresponding with the shortest phase of initial growth, occurred at 25-30 °C and 0.99 a w. Under silk inoculation with this isolate, the hybrid EP10 × EC22 accumulated significantly less FBs than the other hybrids, whereas, under kernel inoculation, differences among hybrids were not significant (P ≤ 0.05). The local isolate of F. verticillioides produced FBs and responded to the usual environmental conditions during maize kernel ripening in northwestern Spain. Inoculation with this isolate is recommended because it is aggressive, toxigenic, and adapted to the local environment. Silk inoculation was the only method that allowed a clear distinction among genotypes based on differences in resistance to FB accumulation. Resistance to natural and artificial inoculations was confirmed for the hybrid EP10 × EC22. © 2013 KNPV. ; MINECO ; Autonomous Government of Galicia ; Excma. Diputación Provincial de Pontevedra ; Spanish Council of Research ; European Social Fund ; This research was supported by the National Plan for Research and Development of Spain (AGL2009-12770), the Autonomous Government of Galicia (PGIDIT06TAL40301PR) and the Excma. Diputación Provincial de Pontevedra. A. Cao acknowledges funding from the JAE Program of the Spanish Council of Research. R.Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; Peer Reviewed

In Southern Europe where whole maize kernels are ground and used for making bread and other food products, infection of the kernels by Fusarium verticillioides and subsequent fumonisin contamination pose a serious safety issue. The influence of environmental factors on this fungal infection and mycotoxin accumulation as the kernel develops has not been fully determined, especially in such food grade maize. The objectives of the present study were to determine which environmental factors may contribute to kernel invasion by F. verticillioides and fumonisin accumulation as kernels develop and dry in naturally infected white maize. Three maize hybrids were planted at two different sowing dates and kernel samples were collected 20, 40, 60, 80 and 100. days after silking. The percentage of kernels infected, and ergosterol and fumonisin contents were recorded for each sampling. F. verticillioides was the most prevalent species identified as the kernels developed. Temperature and moisture conditions during the first 80. days after silking favored natural kernel infection by F. verticillioides rather than by Aspergillus or Penicillium species. Fumonisin was found in kernels as early as 20. days after silking however significant fumonisin accumulation above levels acceptable in the EU did not occur until after physiological maturity of the kernel indicating that kernel drying in the field poses a high risk. Our results suggest that this could be due to increasing kernel damage by insects that favor fungal development, such as the damage by the moth Sitotroga cerealella, and to the occurrence of stress conditions for F. verticillioides growth that could trigger fumonisin biosynthesis, such as exposure to suboptimal temperatures for growth simultaneously with low water activity. © 2013 Elsevier B.V. ; MICINN ; Spanish Council of Research ; Autonomous Government of Galicia ; European Social Fund ; This research was supported by the National Plan for Research and Development of Spain (AGL2009-12770). A. Cao acknowledges funding from the JAE Program of the Spanish Council of Research. R. Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; Peer Reviewed

In northwestern Spain, where weather is rainy and mild throughout the year, Fusarium verticillioides is the most prevalent fungus in kernels and a significant risk of fumonisin contamination has been exposed. In this study, detailed information about environmental and maize genotypic factors affecting F. verticillioides infection, fungal growth and fumonisin content in maize kernels was obtained in order to establish control points to reduce fumonisin contamination. Evaluations were conducted in a total of 36 environments and factorial regression analyses were performed to determine the contribution of each factor to variability among environments, genotypes, and genotype × environment interactions for F. verticillioides infection, fungal growth and fumonisin content. Flowering and kernel drying were the most critical periods throughout the growing season for F. verticillioides infection and fumonisin contamination. Around flowering, wetter and cooler conditions limited F. verticillioides infection and growth, and high temperatures increased fumonisin contents. During kernel drying, increased damaged kernels favored fungal growth, and higher ear damage by corn borers and hard rainfall favored fumonisin accumulation. Later planting dates and especially earlier harvest dates reduced the risk of fumonisin contamination, possibly due to reduced incidence of insects and accumulation of rainfall during the kernel drying period. The use of maize varieties resistant to Sitotroga cerealella, with good husk coverage and non-excessive pericarp thickness could also be useful to reduce fumonisin contamination of maize kernels. ; MICINN ; Autonomous Government of Galicia ; Deputación de Pontevedra ; Spanish Council of Research ; European Social Fund ; This research was supported by the National Plan for Research and Development of Spain (AGL2009-12770), the Autonomous Government of Galicia (PGIDIT06TAL40301PR) and the."Deputación de Pontevedra". A. Cao acknowledges funding from the JAE Program of the Spanish Council of Research. R. Santiago acknowledges postdoctoral contract "Isidro Parga Pondal" supported by the Autonomous Government of Galicia and the European Social Fund. ; Peer reviewed