Fungal contamination and selected mycotoxins in pre- and post-harvest maize in Honduras.

Sixty nine samples of maize were collected from pre-harvest standing crops and on-farm storage facilities from 52 smallholder farms located within 4 regions of Honduras during October 1992 and November 1993. Samples were visually assessed for insect damage and fungal spoilage, and the mycoflora quantified on artificial media. The major components of the ear rot complex were: Fusarium moniliforme, F. moniliforme var. subglutinans, Penicillium species, Stenocarpella maydis, S. macrospora and Acremonium spp. Representative samples were also assayed for mycotoxin content. Fumonisin B1 was detected in all 24 samples tested at levels of between 68-6,555 (micrograms/kg), and aflatoxin was detected in 2 samples heavily contaminated with Aspergillus flavus. Moniliformin and tenuazonic acid were not detected in the samples tested. The implications of these findings for human and livestock health risk are discussed, together with possible strategies for controlling these pathogens.

THE EFFECT OF A PHYTOTOXIN FROM ALTERNARIA BRASSICICOLA ON BRASSICA POLLEN.

A methanol-soluble extract from the culture filtrate of Alternaria brassicicola (Schw.) Wilts., grey leaf spot, markedly inhibited pollen germination and pollen tube growth of Brassica napus L., Brassica campestris L. and Brassica oleracea L. in hanging drop culture at concentrations comparable to those causing death of B. napus secondary embryoids. The extract was partially purified by Sephadex column chromatography, and the fractions obtained were tested for their inhibitory capacity. Two fractions which killed secondary embryoids also inhibited pollen germination. The methanol-soluble extract and inhibitory fractions from Sephadex chromatography were further tested using a thin-layer chromatographic bioassay which showed that the original extract could be separated into at least four inhibitory compounds. The potential of the techniques used for screening and selection for resistance to compounds toxic to plants is briefly outlined.