The use of newly isolated Streptomyces Streptomyces strain TN258 as potential biocontrol agent of potato tubers leak caused by Pythium ultimum Pythium ultimum

摘要

An actinomycete strain designated TN258, was isolated from Tunisian Sahara soil and selected for its antagonistic activity, especially againstPythium ultimum (P. ultimum ) causing potato tubers leak. Based on the results of cultural characteristic of TN258 strain, the 16S rRNA gene nucleotide sequence (1433 bp, accession n?HE600071) and the phylogenetic analysis, we propose the assignment of our new isolate bacterium asStreptomyces TN258 strain. After culture optimization, the inhibitory effect of TN258 free cell supernatant againstP. ultimum was evaluated. As result, by application of 50% (v/v) from 25 mg ml1 of concentration, mycelial growth was totally inhibited with hyphal destruction. At the same concentration, the oospores were distorted and the germination was completely stopped. In potato tubers,Streptomyces TN258 filtrated supernatant, applied 24 h before inoculation byP. ultimum (preventive treatment group) was able to significantly decrease pathogen penetration by 62% and to reduce the percentage of weight loss by 59.43%, in comparison with nontreated group.