Diagnosis of soil-borne fungal factors causing problems in wheat cultivation areas of Kyrgyzstan

Fungal species associated with wheat crown and root rot diseases cause significant damage in many regions worldwide. In this study, fungal species associated with wheat crown/root rot were investigated in the three main wheat production regions in northern Kyrgyzstan. A total of 598 fungal isolates from symptomatic tissues were identified using morphological, microscopic characteristics, and sequence analyses of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA, translation elongation factor 1α (TEF1), and RNA polymerase II beta subunit (RPB2) genes. The percentage of areas from which each fungus was isolated and the ratio of isolation levels were determined. The common root rot agent, Bipolaris sorokiniana, was detected in 86.67% of the surveyed areas, with an isolation frequency of 40.64%. Fusarium spp. constituted 53.01% of all isolates obtained and were classified into 12 different species. The most commonly identified Fusarium species was Fusarium acuminatum, isolated from 70% of the surveyed regions, with an isolation frequency of 21.57%. This species was followed by F. culmorum, F. nygamai, F. oxysporum, and F. equiseti. Pathogenicity studies conducted on susceptible Triticum aestivum cv. Seri 82 showed that F. pseudograminearum and F. culmorum isolates were equally the most virulent pathogens. Bipolaris sorokiniana, being moderately virulent, is considered a serious threat to wheat culture due to its prevalence. In wheat production regions, Fusarium species other than F. culmorum, such as F. acuminatum, F. nygamai, F. oxysporum, and F. equiseti, were found to be non- pathogenic, while less common species like F. redolens, F. algeriense, and F. pseudograminearum were virulent. Curvularia inaequalis, found in three different areas, was mildly virulent, while F. solani, F. proliferatum, F. burgessii, F. tricinctum, along with Microdochium bolleyi, Microdochium nivale, and Macrophomina phaseolina species were found to be non-pathogenic. These species have been considered as secondary colonizers. This study is the most detailed report on the relative importance and distribution of pathogens associated with wheat crown/root rot in Kyrgyzstan. The results of the study provide significant contributions to the literature and to the development of resistant wheat breeding efforts.