Response of near isogenic sorghum lines, differing at the P locus for plant color, to grain mold and head smut fungi

Authors: Funnell-Harris, Deanna; Prom, Louis; Sattler, Scott; Pedersen, Jeffrey

Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2013
Publication Date: 6/12/2013
Citation: Funnell-Harris, D.L., Prom, L.K., Sattler, S.E., Pedersen, J.F. 2013. Response of near isogenic sorghum lines, differing at the P locus for plant color, to grain mold and head smut fungi. Annals of Applied Biology. 163:91-101.

Interpretive Summary: Unpigmented sorghum grain (white) grown on unpigmented (tan) plants is highly desirable for food and animal feed as opposed to pigmented (red) grain or white grain grown on pigmented (purple) plants. The question was asked whether plant pigments protect against two fungal diseases affecting grain: grain mold and head smut. Purple and tan plants with white grain were grown at Lincoln and Ithaca, Nebraska, and Corpus Christi, Texas. Mature seeds were tested for infection by the grain molds, Alternaria, Fusarium and Curvularia. More Fusarium and Curvularia were recovered from grain grown at Corpus Christi; however there was no indication that purple plants had grain more resistant to any of the fungi. Another fungus, Sporisorium reilianum, causes head smut by infecting the plant during seedling stage and growing up through the plant and into the panicle where the seeds are replaced by fungal spores. Head smut is a common sorghum disease in Corpus Christi and, unexpectedly, purple plants were more susceptible to this disease than tan plants. These results indicate that sorghum grain grown on tan plants will not result in greater grain mold and head smut infection rates.

Technical Abstract: Leaves and stalks of many sorghum genotypes accumulate dark red or purple pigments upon wounding while some plants, called “tan,” do not. Grains with unpigmented “white” pericarps grown on tan plants are more desirable for food. The hypothesis tested was that pigments in plants protected grain against the panicle diseases grain mold and head smut. Near isogenic tan or purple plant color genotypes with white grain were planted at Lincoln and Ithaca, NE, and Corpus Christi, TX. The field grown grain was plated onto semi-selective media to detect the presence of grain colonization by mold genera Alternaria, Fusarium and Curvularia. More Fusarium and Curvularia spp. were recovered from grain grown at Corpus Christi than the Nebraska locations; however there was no indication that the grain from purple plants was more resistant to the three fungal genera. Most fungi were identified morphologically as Alternaria alternata. Molecular identification of Fusarium species, using translation elongation factor 1-a gene sequences, showed that Fusarium thapsinum and Fusarium proliferatum infected grain at all three locations. Head smut disease of panicles, caused by the fungus Sporisorium reilianum, was assessed at Corpus Christi; surprisingly, purple plants had significantly greater disease incidence than tan plants. We propose that the tan plant color lines with white grain are promising for development of food grade sorghums not less susceptible than pigmented lines to grain mold and head smut.