Characterization and identification of hot pepper-associated endospore-forming bacteria with potential applications as biofertilizers and in biocontrol of pepper wilt pathogens.

Abstract

Background: Although hot pepper contributes significantly to Ethiopia's national economy, its production is hindered by devastating outbreaks of phytopathogens such as Fusarium wilt and Meloidogyne incognita disease complexes. It is known that bacteria in the pepper rhizosphere can promote plant growth by suppressing soil-borne pathogens and producing growth-promoting substances. Therefore, hot pepper-associated endospore-forming bacteria were evaluated for plant growth-promoting traits and in vitro antagonism to pepper wilt-causing pathogens, revealing some potentially valuable isolates.

Results: One hundred and forty-seven heat-resistant endospore-forming rhizobacteria were recovered from 48 rhizosphere samples. Thirty-five of these isolates solubilized phosphate efficiently with solubilization index values of 2.8-10, and produced indole acetic acid (27. 31-59.16 µg/ml). Moreover, 20 isolates hydrolyzed chitin effectively, 21 of them reduced the radial growth of three pathogenic Fusarium oxysporum strains by between 26.7% and 79.2%, and cell-free supernatants of 12 isolates reduced the hatching of M. incognita eggs by 51-96.4% while also increasing juvenile mortality by 45-98.7%. After 16S rRNA gene sequence analysis, 31 of the isolates were identified as Bacillus spp. (B. siamensis, B. velezensis, and B. cereus; n = 26) and Paenibacillus polymyxa (n = 5).

Conclusions: The bacterial strains JUBC7 (B. cereus) and JUBC12 (B. siamensis) have multiple phytobeneficial traits that make them promising microbial inoculants for protecting high value crops against phytopathogens.