Molecular and Pathogenic Characterization of Fusarium Species Associated with Dry Rot in Stored Potatoes in Kyrgyzstan

Abstract

Fusarium dry rot is a significant fungal disease impacting postharvest potato tubers worldwide, leading to substantial losses in tuber quality, nutritional value, and seed viability. In Kyrgyzstan, where potato is a staple crop, the disease poses a critical threat to food security. This study aimed to identify and characterize Fusarium species associated with dry rot in stored potatoes from the Osh region, a major potato production area facing severe postharvest challenges. Surveys were conducted in 34 potato storage facilities across four districts, and symptomatic tubers were collected. Fifty-four Fusarium isolates were obtained and subjected to a comprehensive characterization approach, including morphological assessments, molecular analyses using iPBS markers based on retrotransposons, DNA sequencing of the translation elongation factor-1 alpha (TEF1) locus, and pathogenicity tests on the 'Soraya' potato cultivar. Fusarium sambucinum was the most prevalent species (50%), followed by F. oxysporum (similar to 17%), F. flocciferum (similar to 11%), F. equiseti (similar to 9%), F. proliferatum (similar to 5%), F. acuminatum (similar to 4%), F. solani (similar to 2%), and F. venenatum (similar to 2%). Morphological identifications were supported by iPBS2395 primer analysis, which revealed distinct DNA fingerprinting patterns among the isolates. Phylogenetic analysis of TEF1 gene sequences further confirmed species identifications, demonstrating strong congruence between morphological, iPBS, and TEF1 data. Pathogenicity tests revealed varying levels of virulence across species, with F. sambucinum exhibiting the highest overall virulence and mean lesion sizes comparable to those of F. flocciferum, while F. equiseti and F. solani showed significantly lower virulence. Except for F. sambucinum, all other Fusarium species represent first reports in Kyrgyzstan, with F. flocciferum being reported globally for the first time as a causal agent of potato dry rot. This study provides a comprehensive assessment of the Fusarium species involved in dry rot in the Osh region, highlighting the dominance of F. sambucinum and the need for enhanced management strategies to mitigate postharvest losses and strengthen food security in Kyrgyzstan.