Pseudomonas and Burkholderia inhibit growth and asexual development of Phytophthora capsici
AbstractThe objective of this study was to isolate and characterize antagonistic rhizobacteria from chili against a notorious phytopathogenPhytophthora capsici. Among the 48 bacteria isolated, BTLbbc-02, BTLbbc-03, and BTLbbc-05 were selected based on their inhibitory activity againstP. capsici. They were tentatively identified asBurkholderia metallicaBTLbbc-02, Burkholderia cepaciaBTLbbc-03, andPseudomonas aeruginosaBTLbbc-05, respectively, based on their 16S rRNA gene sequencing. All inhibited the growth ofP. capsiciat varying levels by inducing characteristic morphological alterations ofP. capsicihyphae. The cell-free culture supernatant of all three isolates impaired motility (up to 100%) and caused lysis (up to 50%) of the halted zoospores. Bioassays revealed thatPseudomonassp. had higher antagonism and zoospore motility-inhibitory effects againstP. capsicicompared with two other isolates,Burkholderiaspp. andB. metallica, which caused vacuolation in mycelium. All three bacteria suppressed sporangium formation and zoosporogenesis ofP. capsici, and improved the seed germination and growth of cucumber. Our findings suggest that epiphytic bacteria,B. metallica,B. cepacia, andP. aeruginosa, could be used as potential biocontrol agents againstP. capsici. A further study is required to ensure conformity with the existing regulations for soil, plant, and human health.