First report of Alternaria alstroemeriae causing leaf spot of soybean in Uzbekistan based on morphological characterization and ITS phylogenetic analysis

Soybean (Glycine max L.) is an important legume crop valued for its high protein and oil content and its contribution to sustainable agriculture. In Uzbekistan, soybean cultivation has expanded in recent years, increasing the need for accurate identification of fungal pathogens affecting crop production. This study aimed to identify Alternaria species associated with soybean leaf spot using morphological characteristics and molecular analysis. Symptomatic soybean leaves were collected from fields in the Syrdarya region, and three fungal isolates were obtained. Colony morphology and microscopic examination revealed characteristics typical of Alternaria, including dark olivaceous colonies, septate conidiophores, and muriform conidia. A representative isolate (R-21) was subjected to ITS rDNA sequencing, and phylogenetic analysis confirmed its close relationship with reference isolates of Alternaria alstroemeriae available in GenBank. The combined morphological and molecular evidence identified the isolate as A. alstroemeriae associated with soybean leaf spot in Uzbekistan. Although pathogenicity tests and multilocus phylogenetic analyses were beyond the scope of the present study, these findings provide the first molecular evidence of the occurrence of A. alstroemeriae associated with soybean leaf spot in Uzbekistan. The results establish a baseline for future studies on pathogenicity, population diversity, epidemiology, and integrated disease management of this pathogen.

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