Evaluation of the efficacy of Bacillus isolates in the biocontrol of cucumber root rot caused by Neocosmospora cucurbitae

Document Type : Research Article

Authors

1 Department of Crop Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.

2 Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract

Neocosmospora cucurbitae (syn. Fusarium solani f. sp. cucurbitae) is an important soil-borne pathogen of cucurbit plants, causing root, crown, and fruit rot. In this research, the efficacy of volatile and non-volatile compounds from eight Bacillus isolates against this pathogen was evaluated under laboratory and greenhouse conditions. In the dual-culture assay, isolate TR11 and isolate Ba15 showed the highest inhibition of fungal mycelial growth (80.25% and 76.92%, respectively). In the volatile compounds test, isolates Ba15, Ba19, and Ba1 showed the highest inhibitory effects. Similar results were observed in the volatile compounds test conducted in Petri dishes containing field soil. The culture filtrates of isolates Ba15 and Ba19 caused the highest inhibition of fungal growth in the laboratory (70.7% and 63.7%, respectively) and led to hyphal deformations, including coiling and fragmentation. In greenhouse conditions, the Ba15 treatment and the Iprodione-Carbendazim fungicide showed acceptable performance in the biocontrol of F. solani f. sp. cucurbitae, with a disease incidence of 66.7% and a control efficacy of 33.4%. Furthermore, Ba19 and Ba15 increased the stem length (42.8% and 26.3%, respectively) and root length (43.7% and 35.7%, respectively) of cucumber plants compared to the infected control. Based on phylogenetic analysis of the 16S rRNA gene, Ba15 and TR11 were grouped with the B. subtilis group, and Ba19 was clustered with B. cereus. The isolates Ba15 (produces volatiles and non-volatiles) and Ba19 (as a growth promoter) are promising candidates for controlling Fusarium root rot of cucumber caused by Neocosmospora cucurbitae.

Keywords

Iranian Journal of Plant Pathology
Volume 60, Issue 4
December 2025
Pages 342-363

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