Chiang Mai Journal of Science

      Fruit rot and anthracnose are the main diseases in avocado fruits caused by fungal species. Solving this problem with chemical reagents has led to human health and pollution problems. Therefore, this study was aimed to select antagonistic bacteria to control those pathogenic fungi. The pathogenic fungi were isolated from avocado fruit occurred fruit rot or anthracnose symptoms. Based on morphological characteristics and the BLASTn results of sequences of the internal transcribed spacer of ribosomal DNA, the obtained fungal isolates belonged to three fungal genera, namely Fusarium, Lasiodiplodia and Colletotrichum, which was the most commonly occurring. Pathogenicity tests were evaluated on avocado fruit. Then the rhizosphere bacteria were isolated from the avocado rhizosphere. To study antagonistic activity, 101 bacterial isolates were cultured with five fungal pathogens using dual culture technique. The bacterial isolate AS80 exhibited high potential to against Fusarium sp. (61.7%), Lasiodiplodia sp. (66.7%) and Colletotrichum sp. (74.1%). The strain AS80 was used to evaluate the efficacy control of Fusarium sp. on “Hass” avocado fruit. The in vivo evaluation revealed that AS80 showed high efficacy against Fusarium sp. The 16s ribosomal DNA sequencing indicated that AS80 was similar to Bacillus subtilis (99.53 %). Further study under field conditions should be done to validate their efficacy.