Submitted to: Journal of New Seeds
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2004
Publication Date: N/A
Interpretive Summary: Throughout the world, grain mold is the most important disease of sorghum, especially in areas with frequent rains late in the growing season. Seeds infected with grain mold have lower yield and quality. Although many fungal species are thought to cause grain mold, Fusarium thapsinum and Curvularia lunata are the two most common fungal species associated with moldy grain in the United States. In order to develop cost-effective control methods, it is important to know the effects of these two pathogens on germination rates of different sorghum cultivars and on other fungal species that can infect or contaminate mature grain. Eight sorghum cultivars were tested with each fungus and a mixture of the two fungi. The study showed that the fungal treatments reduced seed germination rates and caused poor plant establishment. In drier conditions, C. lunata caused lower germination rates in most sorghum lines, while F. thapsinum caused more damage to the seed when conditions are wet. The use of a mixture of the two fungi did not reduce germination rates as much as either of the fungi applied individually. The study also has shown that the environmental conditions during the growing season very much affect the number and types of fungal species infecting or contaminating mature sorghum grain. Some of these fungal species had negative relationships with the two fungal species used in this study. In fact, these species contaminating mature sorghum grain can interfere with the abitity of other fungal species to cause disease or reduce seed germination. In the future, the results of this study will help us to know which sorghum lines to plant in a particular location, and whether other fungal species recovered from sorghum grain can be used as natural control agents for grain mold.
Technical Abstract: Grain mold caused by several species of fungi reduces grain yield and quality. This study examined the effect of the two most common grain mold fungi, Fusarium thapsinum and Curvularia lunata, inoculated singly and together on germination and seed mycoflora. The response to grain mold was evaluated on eight sorghum cultivars in 2000 and 2001 at College Station, TX. Main effects of cultivar (Cul), treatment (Trt), and Cul x Trt interactions for germination were highly significant in both years. Germination was significantly affected by all fungal treatments. Curvularia lunata had the highest negative effect on germination in 2000, while F. thapsinum produced the most significant reduction in germination in 2001. C. lunata was the most frequently isolated fungal species followed by F. thapsinum and F. semitectum. Non-inoculated control samples had Alternaria spp. and F. semitectum as the most frequently recovered fungal species followed by C. lunata. There were highly significant negative correlations between germination and C. lunata (r= -0.44 and P<0.01) in 2000 and between germination and F. thapsinum (r=-0.52 and P<0.01) in 2001. Significant negative correlations between F. thapsinum and C. lunata were observed. Data from this study indicate that the fungal species present, the environment, and the sorghum cultivar all influence seed mycoflora and germination rates.