Mycoflora analysis and other measured parameters of sorghum seeds collected from Puerto Rico and Mexico

Authors: Prom, Louis; Cuevas, Hugo; ISAKEIT, THOMAS - Texas A&M University; PERUMAL, RAMASAMY - Kansas State University; ERATHAIMUTHU, SARADHA - Texas A&M University

Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2018
Publication Date: 11/1/2018
Citation: Prom, L.K., Cuevas, H.E., Isakeit, T., Perumal, R., Erathaimuthu, S. 2018. Mycoflora analysis and other measured parameters of sorghum seeds collected from Puerto Rico and Mexico. Plant Pathology Journal. 17(2):80-86. https://doi.org/10.3923/ppj.2018.80.86.
DOI: https://doi.org/10.3923/ppj.2018.80.86

Interpretive Summary: Worldwide, grain mold is the most important sorghum disease, especially in areas with wet conditions late in the growing season where yield losses in susceptible lines can reach 100%. This disease is caused by a large number of fungal species. In this study, several fungal species, including Fusarium semitectum, F. thapsinum, F. incarnatum, F. acuminatum, F. equiseti, Curvularia lunata, Aspergillus niger, Alternaria, spp, Bipolaris spp, and Penicillium spp. were found infecting or contaminating sorghum seeds collected from Puerto Rico and Mexico. Among the lines collected, only KS-963 collected from Guayanilla, Puerto Rico, exhibited a moderate resistance response to grain mold, while the other sorghum lines were either moderately susceptible or susceptible. F. thapsinum, F. nygamy and C. lunata are considered the most common grain mold species; however, the frequency of recovery of these three fungal species in some sorghum growing regions, including locations surveyed in this study, may be low. Thus, in grain mold resistance studies, selecting the most dominant fungal species in a sorghum growing region and using them as inocula in either the field or greenhouse is more practical and beneficial.

Technical Abstract: Grain mold is one of the major biotic constraints to sorghum production worldwide. This disease complex is associated with many genera of fungi, including mycotoxigenic Fusarium species. Yield losses can be high, especially when susceptible lines are planted in areas with wet conditions later in the growing season. The aim of this study was to determine the frequency of fungal genera/species contaminating sorghum seeds, grain mold severity, seed weight, and germination rate. During the 2016 and 2017 growing seasons, 62 sorghum lines were collected from Puerto Rico and Mexico. In Isabela, Puerto Rico, Fusarium thapsinum was the dominant fungal species isolated from sorghum grain, followed by Aspergillus spp., and F. semitectum in 2016, and in 2017, F. semitectum was the most frequently isolated fungal species. In Guayanilla, Puerto Rico, and Puerto Vallarta, Mexico, FIESC (Fusarium incarnatum, F. acuminatum, F. equiseti, & F. semitectum Complex) were the dominant species isolated from sorghum seed samples. Among the sorghum lines evaluated for grain mold severity, KS-963 collected from Guayanilla, Puerto Rico, exhibited a moderate resistance response to grain mold, while the other sorghum lines were either moderately susceptible or susceptible. Across locations, KS-835 exhibited the highest seed weight (4.7g) while PI534152 exhibited the lowest seed weight (1.0g). Germination rates ranged from 100% to 0% among the sorghum lines surveyed. While F. thapsinum, F. nygamy and C. lunata are considered the most common grain molding species; however, the frequency of recovery of these three fungal species in some sorghum growing regions, including locations surveyed in this study may be low. Thus, in grain mold resistance studies, selecting the most dominant fungal species in a sorghum growing region and using them as inocula in either the field or greenhouse is more practical and beneficial.