Seminar: Genetic Diversity and Pathogenicity of Sorghum-Associated Fusarium spp.

Dr. Vuyiswa Bushula-Njah, Postdoctoral Fellow, Forestry and Agricultural Biotechnology Institute, University of Pretoria
Credit: Vuyiswa Bushula-Njah, FABI, cropped

Credit: Vuyiswa Bushula-Njah, FABI, cropped

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November 27, 2017, 3:35 PM - 4:30 PM

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Dr. Vuyiswa Bushula-Njah is a postdoctoral fellow at the Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa. Her research interests include understanding population genetics, species evolution, life cycle definitions, and pathogenicity of mutually interesting Fusarium species. Vuyiswa received her Bachelor’s and Master’s from Stellenbosch University, South Africa, and her doctoral degree in Plant Pathology from Kansas State.


Understanding the genetic structure of fungal pathogens allows us to predict their evolutionary potential, which aids in informed decision-making regarding disease management strategies. The genetic structure of Fusarium thapsinum and F. andiyazi, two important pathogens that cause grain mold and stalk rot of sorghum (Sorghum bicolor), are little understood.

First, the genetic structure and pathogenicity of a F. thapsinum population from sorghum in Kansas were investigated using amplified fragment length polymorphisms (AFLPs), vegetative compatibility groups (VCGs), sexual cross-fertility, and seedling pathogenicity. Two sympatric populations and a genetically intermediate hybrid group were identified within this species. Seedling pathogenicity varied, which may be partially attributable to genetic variability in the F. thapsinum populations.

Second, genetic relatedness of F. thapsinum from sorghum in Kansas, Australia, Thailand, and three African countries (Cameroon, Mali, and Uganda) was evaluated using AFLP markers and sexual crosses. Populations from Australia and Thailand were more closely related to Kansas than they were to Africa. This result suggested that, outside of Africa, there is significant differentiation among F. thapsinum populations and suggested Africa is not the only source population of F. thapsinum in Kansas, Thailand, and Australia.

Third, sorghum stalk rot was evaluated by inoculation with six genetically diverse F. thapsinum strains under field and greenhouse conditions. A susceptible line, Tx7000, and two resistant lines, SC599 and BTx399, were evaluated in the field. Only Tx7000 and SC599 were evaluated in the greenhouse. Based on major lesion length and the number of nodes crossed by the lesion, there were differences in stalk rot aggressiveness among F. thapsinum strains. This result highlights the importance of challenging germplasm with well-characterized strains that represent the genetic spectrum of F. thapsinum.

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