Survey of fluorescent pseudomonads from rhizosphere and rhizoplane of tomato for biocontrol of Clavibacter michiganensis subsp. michiganensis

Tomato bacterial wilt and canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm) is an economically important seed-borne disease in the major tomato growing regions all over the world. Also, this disease is present in northern, northwestern, and central provinces of Iran. This study aimed to isolate fluorescent pseudomonads with efficient antagonistic activity against Cmm from tomato rhizosphere and rhizoplane. In the present study, ninety six fluorescent pseudomonads were isolated from rhizosphere and rhizoplane of tomato plants using King’s medium B agar and tested for antagonistic activity against Cmm by co-inoculation culture in vitro. Seed and roots of tomato transplants were inoculated with representative antagonistic strains and planted in the soil infected by Cmm in greenhouse. The incidence and severity of the disease were assessed on tomato as well as growth parameters. Nineteen strains exhibited inhibitory activity against Cmm in vitro and two selected strains (M۱R۱ and H۱R۱) were identified as Pseudomonas putida based on their phenotypic characteristics and partial ۱۶S rRNA gene sequences. These two strains produced siderophore and hydrogen cyanide. In greenhouse, strain M۱R۱ reduced the disease incidence by ۳۰% and ۴۰% in Superluna and Falat cultivars, respectively. Strain H۱R۱ reduced the disease incidence by ۲۰% only in Falat cultivar. Strains M۱R۱ and H۱R۱ decreased the disease severity by ۵۲.۹۳ % and ۱۰.۶۰ % in Superluna and ۴۷.۹۰ % and ۴۲.۸۸ % in Falat cultivars, respectively. Strain M۱R۱ increased the growth parameters, including fresh and dry weight, and height of the inoculated plants significantly in comparison with control. These results indicated that rhizospheric fluorescent pseudomonads could be effective agents in the biocontrol of tomato bacterial wilt and canker disease.

کلیدواژه ها:

Antagonistic activity ، Biological control ، Pseudomonas putida ، Siderophore ، Tomato bacterial canker