Fusarium moniliforme and Fusarium proliferatum are the most frequently isolated fungi from maize (Zea mays L.) in Spain. Both Fusarium species produce toxins potentially dangerous for animals and humans, the fumonisins being the most significant of those toxins. White maize is preferred for human consumption, and extra care should be taken to avoid kernel mycotoxin contamination. The objectives of this study were to identify and quantify kernel infection by Fusarium spp. and contamination by fumonisin on white maize hybrids, to search for white maize sources of resistance to infection by Fusarium spp. and mycotoxin contamination, and to preliminarily study the genetics involved in such resistances. Ten F(1) single crosses derived from a diallel mating design among five white maize inbreds were evaluated in a randomized complete block design with three replications in 2002 at two locations. Fusarium verticilloides and F. proliferatum were detected on kernels of white maize hybrids cultivated in northwestern Spain. No differences in fungal infection were found among maize genotypes, but differences in fumonisin contamination were significant and could be related, in part, to differences in husk tightness. Among the genotypes studied, general combining ability (GCA) effects were the most important for resistance to fumonisin contamination. Inbreds EP10 and EC22 showed the most favorable GCA effects for husk tightness and fumonisin content, and the cross between them, EP10 x EC22, had the most favorable specific combining ability (SCA) effect for husk tightness. Inbreds EP10 and EC22 showed favorable GCA effects for fumonisin contamination and husk tightness, and the cross EP10 x EC22 was the only one with an average fumonisin level below 1 mug/g. Although this should be confirmed with more extensive studies, white maize inbreds developed from white maize landraces could be sources of resistance to fumonisin contamination.

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Fusarium poses food and feed safety problems because most species produce mycotoxins. To understand the epidemiology of the Fusarium disease, efforts must focus more precisely on how environmental variables affect disease presence. The objectives of the present study were to monitor the occurrence of Fusarium species in maize kernels in northwestern Spain to determine the risk of mycotoxin contamination and to identify environmental traits affecting the composition of the Fusarium species identified. A combination of 24 environments was evaluated. The percentage of kernels infected by F. verticillioides ranged from 33 to 99%, supporting the idea that fumonisin contamination is the main maize-based feed and food safety concern in this area. In this region, temperature and humidity primarily affected Fusarium spp. occurrence. Warmer temperatures during the later stages of kernel development and during kernel drying increased the frequency of F. verticillioides in maize kernels, while the presence of F. subglutinans was increased by higher relative humidity during the silking stage and cooler temperatures during kernel drying.

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Papaya ringspot virus type P (PRSV-P) systemically infects Carica papaya and species belonging to the family Cucurbitaceae. Attempts to recover PRSV-P from naturally infected cucurbit plants grown near or among diseased papaya trees have shown conflicting results worldwide. This study aimed to evaluate the natural infection of cucurbit species grown among and near papaya trees infected with PRSV-P in Brazil. Natural infection of cucurbits with PRSV-P occurred in zucchini squash but not in watermelon and cucumber. However, several attempts to recover PRSV-P from numerous Cucurbita pepo cv. Caserta (zucchini squash) plants grown 5-80 m from diseased papaya trees in the field failed. Mechanical inoculations of Cucurbita pepo cv. Caserta, Cucurbita maxima cv. Exposição (pumpkin), Cucumis sativus cv. Primepack Plus (cucumber) and Citrullus lanatus cv. Crimson Sweet (watermelon) with five Brazilian PRSV-P isolates showed that zucchini squash was the most susceptible species followed by watermelon and cucumber, while pumpkin was not infected. The results confirmed the variable susceptibility of cucurbit species to experimental and natural PRSV-P infection. Given these facts, the control of the disease through roguing should focus mainly on diseased papaya plants, as has been practised successfully in Brazil for many years, and on those cucurbits particularly known to be susceptible to natural infection with PRSV-P.