Molecular Characterization of Wheat Leaf Blotch Pathogen (Zymoseptoria Tritici) Isolates from Northern Ethiopia Using Ssr Markers
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Date
2019-06-03
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Addis Ababa University
Abstract
Septoria leaf blotch, caused by Zymoseptoria tritici, is one of the most devastating diseases of wheat. Understanding its genetic diversity is paramount importance in designing effective and sustainable management strategies to control the disease. In Ethiopia, studies on the pathogen identification and genetic diversity are greatly missing. Therefore, the present study was designed to detect and determine the genetic diversity and population structure of Z. tritici isolates collected from northern Ethiopia: Amhara and Tigray regional States using Simple Sequence Repeat (SSR) markers. In this study, a total of 24 single spore derived Z. tritici isolates were subjected to a pair of Z. tritici specific marker (ITS1 and Primer JB446) to confirm the isolates, and nine Simple Sequence Repeat markers to assess their genetic diversity and population structure. The PCR based detection using a pair of primers that target the internal transcribed spacer sequences of rDNA resulted in a positive amplification size of 345 base pair (bp) confirming that all the isolates are Z. tritici. The molecular study revealed a total of 242 bands, out of which 58.3% were found to be polymorphic. All loci across the entire populations were found to be highly (100%) polymorphic and informative with Polymorphic information contents (PIC) ranging from 0.95 (ST1A2) to 0.60 (ST1G7), confirming the power of the markers to be used as molecular tools to determine the extent of genetic diversity and population structure of the pathogen. The genetic diversity across the entire populations ranged from 0.96 (ST1A2) to 0.63 (ST1G70.87) with overall mean of 0.87. Moreover, Analysis of molecular variance (AMOVA) revealed that 95% (3.989) of the total genetic variation (4.19) was accounted within populations, leaving only 5% (0.2) for among populations. The smaller Fixation Index value (0.047) observed in the study indicates the presence of lower population differentiation as a result of higher gene flow (Nm =4.73) between the Z. tritici populations of Amhara and Tigray area. The unweight pair group with methods arithmetic average (UPGMA) based cluster, Principal components of Analysis (PCoA) and Structure analysis poorly grouped the individuals into distinct clusters confirming the presence of population admixture due to the long distance movement of the sexual ascospores. Hence, it is possible to conclude that the present study has successfully identified Z. tritici isolates of Northern Ethiopia and disclosed their genetic diversity and population structure using highly informative molecular marker system. The observed higher genetic diversity in both populations indicates that both regions are hot spot for the pathogen study and also can serve as site for germplasm evaluation. The information is very relevant for wheat breeders and pathologists to design and implement integrated management strategies to control the disease and hence to contribute to increased and stable wheat production and productivity in the regions and in Ethiopia at large.
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Keywords
Identification, Genetic Diversity, Population Structure, Simple Sequence Repeats