Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun)

Fayyadh, M.A. and L.K. Awad. 2021. Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun). Arab Journal of Plant Protection, 39(4): 281-288. https://doi.org/10.22268/AJPP-39.4.281288 This study was conducted in Plant Protection Department, College of Agriculture, University of Basrah during the period 2017-2018 aimed to isolate and identify Actinomycetes from different environmental sources and evaluate their efficiency to control cucumber damping off disease caused by Rhizoctonia solani. 28 isolates of Actinomycetes were isolated from different sources from the Basrah region. All such isolates were gram positive, amylase and catalase positive and they had branched hyphae. Molecular identification following amplification of 16sRNA confirmed that Actinomycetes isolate No 6 isolated from soil had a similarity of 99% with Streptomyces griseus, whereas the isolate No 66 isolated from date palm roots had a similarity of 99% with Brevibacterium celere. The nucleotide sequence of the two isolates has been deposited at NCBI with Genbank accession number LC501385.1 for S. griseus and LC501386.1 for B. celere. The dual culture technique showed that Actinomycetes isolates S. griseus and B. celere had high antagonistic activity against Rhizoctonia solani, which produced inhibition zones of 7 and 15 mm in dimeter, respectively. On the other hand, volatile compoundsreleased from S. griseus and B. celere inhibited the growth of R. solani by 68 and 81.5%, respectively. Pot experiment showed that all actinomycetes isolates significantly reduced cucumber seedling damping–off incidence caused by R. solani. Keywords: Actinomycetes, Rhizoctonia solani, Cucumber, Biological Control