Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2005
Publication Date: 2/1/2006
Citation: Erpelding, J.E., and Prom, L.K. 2006. Seed Mycoflora for Grain Mold from Natural Infection in Sorghum Germplasm Grown at Isabela, Puerto Rico and their Association with Kernel Weight and Germination. Plant Pathology Journal 5(1):106-112. Interpretive Summary: Grain mold is one of the most important diseases of sorghum. Numerous fungal species are capable of infecting sorghum resulting in the production of moldy grain of low quality with reductions in grain yield. Information on the occurrence of the various grain mold fungal species will aid in the evaluation of sorghum lines to identify sources of resistance. The sorghum collection maintained by the US National Plant Germplasm System is being evaluated at the Tropical Agriculture Research Station in Isabela, Puerto Rico and the fungal species responsible for grain mold were surveyed at the research location in 2002 and 2003. Fusarium semitectum was the most frequently occurring fungal species, but other species were also identified from infected grain including Fusarium thapsinum and Curvularia lunata, which are fungal species most commonly associated with grain mold in sorghum. The occurrence and frequency of isolation for the various grain mold fungal species varied between growing seasons and between sorghum lines. A reduction in seed germination was observed with an increase in the incidence of several of the fungal species. Seed germination was not reduced by grain mold infection for several sorghum lines included in the evaluation and this germplasm may provide sources of tolerance to grain mold.
Technical Abstract: Seed mycoflora, kernel weight, and seed germination were evaluated for 20 sorghum germplasm lines naturally infected with grain mold during the 2002 and 2003 growing seasons in Isabela, Puerto Rico. Mycoflora analysis of the kernels revealed Fusarium semitectum as the most frequently recovered fungal species. Fusarium verticillioides, F. thapsinum, other Fusarium species, Curvularia lunata, Bipolaris spp., Alternaria spp., Colletotrichum graminicola, and several unknown fungal species were also isolated from mold infected grain. Bipolaris spp., Alternaria spp., and C. graminicola were isolated at the lowest frequencies from infected grain. Variation was observed in the frequency of fungal species isolated between years and between germplasm lines. Seed germination was positively correlated with kernel weight and negatively correlated with the incidence of F. semitectum, C. lunata, and Bipolaris spp. Non-significant negative associations between germination with Fusarium spp. and between kernel weight with F. semitectum, F. thapsinum, and C. lunata were also observed. Significant negative associations occurred between the incidence of F. semitectum with the frequency of C. lunata and F. thapsinum. The incidence of grain mold did not reduce seed germination for several sorghum lines, suggesting potential sources of tolerance for sorghum improvement.