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Abstract
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Alternaria alternata is a significant fungal species that can function as both an endophytic fungus and a pathogen
in various plant tissues. Unlike pathogenic fungi, endophytic fungi enhance the growth of host plants through
different mechanisms. Studying the genetic diversity of endophytic fungi can provide insights into their coevolution with plants. In this research, the genetic diversity of A. alternata from different hosts was examined
using ten pairs of ISSR primers. Seven of the ten primers generated scorable polymorphic bands (total of 65 bands
with an average of 9.2 bands per primer) for molecular analysis. Genetic diversity parameters revealed that
isolates from Gundelia tournefortii exhibited the highest genetic diversity (Na, Ne, I, and He values of 1.55, 1.45,
0.35, and 0.24, respectively), while isolates from Tamarix ramosissima showed lower diversity (Na, Ne, I, and He
values of 1.18, 1.13, 0.11, and 0.07, respectively). Cluster analysis grouped the isolates into four clusters based
on Jaccard similarity matrix and UPGMA method. Principal coordinate analysis (PCOA) supported the cluster
analysis findings. Analysis of molecular variance (AMOVA) indicated a high level of genetic differentiation
within populations (72 %), with only 28 % of diversity between populations. The genetic structure assessment
revealed a relatively strong genetic structure among populations, suggesting the presence of a hidden sexual
cycle or mitotic recombination as factors contributing to the high genetic differentiation among A. alternata
populations.
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