Isolation and Characterization of a Bacterium as a Biocontrol Agent against Bacterial Wilt and Soft Rot Diseases in Ginger (Zingiber officinale Roscoe)

Abstract

Ginger (Zingiber officinale Roscoe) is one of the important cash crops in India and Southeast Asia; however, its cultivation facing major threats from bacterial wilt, caused by Ralstonia solanacearum Smith (1896) Yabuuchi et al., 1995 and soft rot caused by Pythium myriotylum Drechsler. These pathogens have the ability to cause even hundred percent crop loss under suitable conditions, and traditional control methods have been largely ineffective and costly. In this context, the present study aimed to isolate a soil bacterium from ginger-growing regions in the Wayanad district of Kerala, with dual biocontrol potential against both pathogens, and to evaluate its ability to promote plant growth (PGPR). Ten bacterial isolates were collected from diverse agro-ecological zones with B-1 to B-10 code tags and screened for antifungal and antibacterial activities. Of these isolates, isolate B-2 exhibited the highest inhibition of P. myriotylum (mean radial growth: 6.33±1.46 mm) and R. solanacearum (inhibition zone: 6.00 mm, with an activity index of 0.18). Biochemical analysis detected the production of enzymes such as Amylase, Protease, Gelatinase, Lipase, Catalase, as well as positive results for Indole Acetic Acid (IAA) and ammonia production, confirming PGPR traits. Molecular identification through 16S rDNA sequencing revealed that the isolate was Bacillus cereus, with a 99.74% similarity. These results suggest that Bacillus cereus B-2 is a promising biocontrol agent with PGPR capabilities, offering a cost-effective and eco-friendly alternative for managing ginger diseases and enhancing crop yield. Additionally, it highlights the importance of studying local microorganisms that can control severe crop diseases within the same region. Consideration will also be given to the soil’s recovery capacity and resilience in the face of climate change.