بررسی مقدماتی عوامل خشکیدگی سرشاخه درختان میوه گرمسیری از جنوب شرق ایران

Sistan and Baluchistan and Kerman are among the most important Provinces producing tropical fruits in Iran. Over the past few years, the die-back disease affecting tropical fruit trees such as Christ's thorn jujube, Chico, and Guava has led to significant financial losses for farmers in the region. This study aimed to isolate and identify fungi and investigate their role in causing die-back in Sistan and Baluchistan and Kerman Provinces. Throughout 2022 and 2023, multiple samples were collected from branches showing signs of die-back in Christ's thorn jujube, Chico, and Guava trees. Fungi were isolated on PDA cultures. A total of 213 isolates (183 isolates belonging to six fungal genera and 30 isolates with mycelium growth/as non-spore producing fungi) were isolated from the branches of trees with die-back and identified by microbiological methods. Finally, 15 fungal isolates with different morphological characteristics were selected for DNA extraction and nucleotide homology determination. To confirm the morphological identification, sequencing of ITS1-5.8S-ITS2 (ITS-rDNA), ß-tubulin (tub), and Translation elongation factor-1α (tef-1α) genomic regions was used. Phylogenetic analysis for Didymella isolates using ITS-rDNA and ef-1α gene regions, for Lasiodiplodia isolates using ITS and tub gene regions, for Neopestalotiopsis isolates from ITS-rDNA gene regions, tub and tef-1α and Neocosmospora isolates from ef-1α gene region was done by Maximum Parsimony method. The nucleotide sequence of the ITS-rDNA gene region was registered in the Genebank and the accession number was obtained. The species identified in most studied locations include Didymella porsopidis (accession number: PQ179755), D. chlamydospora (accession number: PQ179754), D. longicola (accession number: PQ179756), Neocosmospora solani, Lasiodiplodia theobromae (accession number: PQ179757), and Neopestalotiopsis sp. (accession number: PQ179758). The pathogenicity tests were carried out for some selected isolates. Results showed that the isolates obtained from the Guava trees were pathogenic to 3-6 months old guava seedlings under greenhouse conditions. In addition, the isolates obtained from the one-year-old Christ's thorn jujube trees only caused symptoms at the inoculation site and necrosis and yellowing in some seedling leaves were eliminated. Fungal isolates obtained from 6-month Chico trees were non-pathogenic under greenhouse conditions.