Screening of Indigenous Rhizospheric Cyanobacteria as Potential Growth Promotor and Biocontrol of Ralstonia syzygii subsp. indonesiensis on Chili

Abstract

The use of microbial inoculants as biofertilizers and/or antagonists of phytopathogens provides a promising alternative to chemical fertilizers and pesticides. Cyanobacteria are a remarkable group of prokaryotes, which are known to exist independently and in symbiotic/facultative associations with a diverse range of members of the plant. Cyanobacteria inoculation had been reported to enhance the growth, nitrogen fixation and yields. Although, their establishment and role in plant growth promotion and biocontrol activity is poorly known. This research purposed to isolate and screen the best indigenous cyanobacteria from chili rhizosphere to promote growth rate and control R. syzygii subsp. indonesiensis on chili. The study consisted of three parts: (i) isolation and multiplication of the cyanobacteria from soil rhizosphere, and screening through Hypersensitive response (HR) on Mirabilis jalapa for pathogenicity test, (ii) in planta screening of selected cyanobacteria isolates (from second’s step) to increase growth of chili seedlings, and (iv) in planta evaluation of selected cyanobacteria isolates for the control of bacterial wilt disease and promote growth of chili. Cyanobacteria isolated with BG-11 medium and incubated in room temperature with 12/12 h light/dark cycle. 49 cyanobacteria had isolated from chili rhizosphere. All isolates also showed suppression of disease development caused by R. syzygii subsp. indonesiensis. BCBY 3.1.3, and CBY 5.1 showed suppression of symptom appear (60.00 day post inoculation (dpi) compared to control (.38.667 dpi) and also suppressed disease severity (1.67) compared to control (3.00). The two strains which have best ability to increased growth rate also have best ability to fully suppressed disease development with no symptom appear until last day of observation.