Grain mold fungi and their effect on sorghum grain quality.

摘要

The major grain mold fungi of sorghum in South Africa were determined by assaying five sorghum cultivars from three localities in 2002 and eight localities in 2003. The predominant fungal genera from all the cultivars and localities were Alternaria, Curvularia, Epicoccum, Fusarium and Phoma spp. in order of frequency isolated. The relative frequency of grain mold fungal isolates differed with locality. Grain mold fungi were least frequently encountered at Bethlehem followed by Heilbron. The incidence of grain mold fungi correlated negatively with milling quality and certain malting properties of sorghum grain were affected. The effect of fungal isolates on various grain quality parameters was examined by inoculating sorghum panicles under glasshouse conditions. All inoculated fungi reduced grain germination in a range of 5.0-50.1% with Curvularia lunata resulting in the highest reduction (50.1%) followed by a mixed population of fungi (30.2%). Fusarium proliferatum, A. alternata, F. graminearum, P. sorghina and an inoculum mixture of equal proportions of the five test fungi significantly (P<=0.05) reduced 1000 kernel mass by 31.5, 26.2, 21.3, 10.6 and 7.4%, respectively. Fusarium thapsinum and C. lunata yielded a 3.8 and 0.5% reduction in 1000 kernel mass, respectively. Fusarium thapsinum, F. proliferatum and the mixed fungal population followed by P. sorghina, C. lunata and A. alternata resulted in higher levels of grain discolouration in glasshouse studies. A significant increase in mycotoxin concentration on grains inoculated with different grain mold fungi was recorded. These results indicated that various fungi are involved in the grain mold disease complex and that both qualitative and quantitative losses of sorghum may result.