The Efficacy of Local Streptomyces Diastatochromogenes Isolate as a Biological Control Agent of Potato Tuber Soft Rot Disease Caused by Pectobacterium carotovorum in Iraq

This study aimed to isolate the biological control agent Streptomyces sp. and evaluate their antagonist activity against bacterial potato soft rot disease caused by Pectobacterium carotovorum . Four Streptomyces sp. were isolated from several potato-grown fields of Baghdad province (Al-Radwaniyah, Al-Yusufiyah, Abu Ghraib, and Al-Taji), and the antibacterial abilities of these isolates were tested against two purified P. carotovorum isolates at the Petrie dish level. Which showed different inhibiting ratios. One S. diastatochromogenes subsp. luteus isolate exhibited a high impact in reducing P . carotovorum on in vitro and store levels. The partial 16S rRNA nucleotide sequence of this biological control agent was recorded for the first time in the GenBank under accession number OQ253505. Moreover, the molecular analysis and the phylogenetic tree of the two purified rotting bacterial isolates were closely related to isolates from China and Germany, implying that they are derived from a different ancestor.