Morganella sp. : A Dual-Action Biocontrol Agent and Growth Promoter against Fusarium oxysporum in Banana

Abstract

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) remains the most critical banana disease that threatens the industry worldwide. Identifying potential biocontrol agents that support host growth is essential in finding effective solutions against Foc. In this study, bacterial isolates from banana pseudostems, rhizomes, and rhizosphere soil were tested for their antifungal activity against Foc and plant growth-promoting effects under nursery conditions. Visual agar plate assay showed that isolates RS13, ER03, and ER20 significantly inhibited Foc growth on days 5, 6, 7, and 8 compared to E. coli (p<0.05). Additionally, these isolates promoted overall banana plantlet growth by increasing recorded values for pseudostem diameter, height, leaf number, and total leaf area. To further investigate the mechanisms that underlie its antifungal and plant growth-promoting activities, the whole genome of RS13 was sequenced and analyzed. Genome assembly identified RS13 as Morganella sp., with functional annotations resembling M. morganii subsp. morganii KT in functional and metabolic profiles. Gene mining revealed RS13 has increased protein members in the Type III secretion system and three chitinases, indicating its potential biocontrol mechanisms against pathogenic fungi compared to M. morganii subsp. morganii KT. Moreover, metabolic predictions indicate RS13's capacity for nitrogen fixation and nitric oxide production, suggesting its capacity to promote plant growth. These findings offer significant insights into the banana microbiome and underscore its potential for fungal biocontrol and plant growth enhancement.