Isolation and screening of phytotoxin-producing actinomycetes for biological control of Cardaria draba

Cardaria draba is an important, troublesome weed in the sustainable production of wheat. In the first step of this study, 100 actinomycete isolates were purified from soil samples collected from the rhizosphere and phyllosphere of plants in different provinces of Iran. All isolates were subjected to primary screening by assaying the fermentation broth of the sterile surfaces of C. draba leaves. Considerable herbicidal activity was observed for four isolates. During secondary screening and assaying of the extracted culture medium with ethyl acetate, two isolates, Streptomyces sp. UTMC 2102 and Streptomyces sp. UTMC 2104, were selected as superior phytotoxin-producing isolates in the biological control of C. draba. Leaf necrosis was observed in 500 and 1000 µg/ml and ≥100 µg/ml dilutions for isolates UTMC 2102 and UTMC 2104, respectively. Phylogenic identification confirmed that the 16S rRNA gene has 100% similarity to Streptomycin anulatus for the isolate Streptomyces sp. UTMC 2102 and 100% similarity to Streptomyces vinaceusdrappus for the isolate Streptomyces sp. UTMC 2104. These results suggest that the S. anulatus and S. vinaceusdrappus isolates can be used in the biological control of C. draba in wheat fields.