Genetic Diversity and Population Structure of Zymoseptoria tritici in Ethiopia as Revealed by Microsatellite Markers

Authors: MEKONNEN, TILAHUN - Addis Ababa University; HAILESELASSIE, TEKLEHAIMANOT - Addis Ababa University; Goodwin, Stephen - Steve; TESFAYEA, KASSAHUN - Addis Ababa University

Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2020
Publication Date: 5/19/2020
Citation: Mekonnen, T., Haileselassie, T., Goodwin, S.B., Tesfayea, K. 2020. Genetic Diversity and Population Structure of Zymoseptoria tritici in Ethiopia as Revealed by Microsatellite Markers. Fungal Genetics and Biology (2020). 141:103413. https://doi.org/10.1016/j.fgb.2020.103413.
DOI: https://doi.org/10.1016/j.fgb.2020.103413

Interpretive Summary: Septoria tritici blotch (STB) is one of the most devastating diseases of wheat. Understanding genetic diversity of the pathogen has supreme importance in developing management strategies. Isolates of Z. tritici representing eight populations from the major wheat-growing areas of Ethiopia were analyzed. The analysis revealed a very high level of genetic variation and very little differentiation, indicating high levels of pathogen migration. Locations with the highest pathogen variation were identified and these disease hot spots could be used to test wheat germplasm for resistance in the future. These results will be of interest to fungal geneticists and evolutionary biologists to better understand variability in this pathogen. Additionally, plant pathologists and wheat breeders will eventually be able to identify and develop better strategies to manage the disease through future testing and deployment of resistant wheat cultivars.

Technical Abstract: Septoria tritici blotch (STB), caused by Zymoseptoria tritici (formerly: Mycosphaerella graminicola or Septoria tritici), is one of the most devastating diseases of wheat globally. Understanding genetic diversity of the pathogen has supreme importance in developing best management strategies. However, there is a dearth of information on the genetic structure of Z. tritici populations in Ethiopia. Therefore, the present study was targeted to uncover the genetic diversity and population structure of Z. tritici populations from the major wheat growing areas of Ethiopia. Totally, 182 Z. tritici isolates representing eight populations were analyzed with 14 microsatellite markers. All the microsatellite loci were polymorphic and highly informative, and hence useful genetic tools to depict the genetic diversity and population structure of the pathogen. Genetic diversity across the entire populations was very high (0.45). Analysis of molecular variance (AMOVA) revealed a low but statistically significant genetic differentiation (PhiPT = 0.08, p = 0.001) with high gene flow (Nm = 5.66). Most (92%) of the total genetic variation resides within populations, leaving only 8% among populations. Cluster (UPGMA) and Structure analysis did not group the populations into sharply distinct clusters, likely due to high gene flow. Among populations, the East Shewa (0.47), Arsi (0.58), South West Shewa (0.5) and Bale (0.48) populations showed higher genetic diversity, and hence these areas can be considered as hot spots for investigations planned on the pathogen and host-pathogen interactions. In conclusion, the pathogen has a broad genetic base, and possibly can change its virulence spectrum which results in frequent host-resistance breakdown. Therefore, integrated disease management strategies shall be deployed to control or minimize wheat yield loss due to septoria tritici blotch.