Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 2011
Publication Date: May 25, 2011
Citation: Funnell-Harris, D.L., Pedersen, J.F. 2011. Presence of Fusarium spp. in air and soil associated with sorghum fields. Plant Disease 95: 648-656. Interpretive Summary: Sorghum grain, valuable for feed, food and bioenergy, can be colonized by several species of the seed mold fungus, Fusarium. The sources of spores of these fungi in Nebraska sorghum fields was determined. Soil and air samples within sorghum fields were sampled and assessed, which provided evidence that spores from these sources could contribute to Fusarium grain infections. Soil population estimates of Fusarium spp. indicated that adequate inoculum for systemic infections, that could lead to infected grain, was present. Fungal spores in air samples within two sorghum fields were collected by passive trapping throughout two growing seasons. Analysis of Fusarium isolates from passive spore traps indicated that spores from pathogens increased from flowering through maturity, which coincides with stages in which developing grain is vulnerable to Fusarium. All Fusarium species previously identified from grain produced in Nebraska were detected by air sampling.
Technical Abstract: Sorghum grain, valuable for feed, food and bioenergy, can be colonized by several Fusarium species; therefore, it was of interest to identify possible sources of conidia. Analysis of air and soil samples provided evidence for the presence of propagules from Fusarium genotypes that may cause grain infections. Soil population estimates of members of the Gibberella fujikuroi species complex that includes sorghum pathogens, and other Fusarium spp., suggested that adequate inoculum for systemic infections was present. Conidia in air samples within two sorghum fields were collected by passive trapping for two years. Sub-sampled Fusarium isolates indicated that numbers of G. fujikuroi increased from anthesis through maturity, which coincides with grain development stages vulnerable to Fusarium. Genotyping using translation elongation factor gene sequences revealed that spore trap isolates included members of G. fujikuroi that are sorghum pathogens: Fusarium thapsinum, Fusarium verticillioides, Fusarium proliferatum, and Fusarium andiyazi. Also detected were Fusarium graminearum, Fusarium subglutinans and several Fusarium incarnatum-F. equiseti species complex haplotypes that colonize sorghum asymptomatically. All commonly-found grain colonizers were detected from air samples in this study.