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Banana is one of the primary fruits cultivated in Malaysia and currently decimated by the emergence of a disease, known as banana blood disease (BBD) which caused by Ralstonia syzygii subsp. celebesensis (Rsc). The BBD has significantly affected the yield and profits of the worldwide banana industry. To date, various approaches including chemical and biological controls have been attempted to manage this disease but none of them succeed in controlling the disease. The uses of lactic acid bacteria (LAB) in managing plant diseases have been reported earlier but little information is available. Therefore, this project is designed to identify and investigate potential plant-associated LAB as biological control agent (BCA) against Rsc by using agar well diffusion method. The inhibition zones of each well were observed after 72h and the isolated LAB that showed inhibition zones were proceed for molecular characterization using PCR amplification followed by gel electrophoresis. The sequences were used for phylogenetic analysis. In addition, each of the potential LAB were used to identify their morphological characterizations and biochemical testing. Throughout the study, the highest inhibition zones of LAB from kimchi and fermented milk achieved a diameter of 21.30 mm and 28.70 mm, respectively. Kimchi isolates showed the highest similarity which is 97% as Lactiplantibacillus plantarum species. Among the fermented milk isolates, the highest similarity which is 98% identified as Lacticaseibacillus paracasei.

Banana is one of the primary fruits cultivated in Malaysia and currently decimated by the emergence of a disease, known as banana blood disease (BBD) which caused by Ralstonia syzygii subsp. celebesensis (Rsc). The BBD has significantly affected the yield and profits of the worldwide banana industry. To date, various approaches including chemical and biological controls have been attempted to manage this disease but none of them succeed in controlling the disease. The uses of lactic acid bacteria (LAB) in managing plant diseases have been reported earlier but little information is available. Therefore, this project is designed to identify and investigate potential plant-associated LAB as biological control agent (BCA) against Rsc by using agar well diffusion method. The inhibition zones of each well were observed after 72h and the isolated LAB that showed inhibition zones were proceed for molecular characterization using PCR amplification followed by gel electrophoresis. The sequences were used for phylogenetic analysis. In addition, each of the potential LAB were used to identify their morphological characterizations and biochemical testing. Throughout the study, the highest inhibition zones of LAB from kimchi and fermented milk achieved a diameter of 21.30 mm and 28.70 mm, respectively. Kimchi isolates showed the highest similarity which is 97% as Lactiplantibacillus plantarum species. Among the fermented milk isolates, the highest similarity which is 98% identified as Lacticaseibacillus paracasei. [ABSTRACT FROM AUTHOR]

Banana blood disease (BBD), a banana wilt disease caused by blood disease bacterium (BDB), Ralstonia syzygii subsp. celebesensis (RSC), was first reported in Malaysia in 2007. BDB results in wilting appearance and internal bleeding-like symptoms, which eventually leads to entire crop loss including ready-harvested fruit bunch. Understanding the pathogenesis of BDB in local common banana cultivars provides good foundation to tailor disease management plan to mitigate BBD. To address this need, our study was performed to characterize BDB isolated from locally grown banana plants and to compare the pathogenesis of the bacterium in four most common local banana cultivars. In this study, BDB isolated from Malaysia's plantation was identified and characterized via the molecular and phenotypic method. The pathogenicity of characterized virulent BDB isolate was determined in four local banana cultivars via disease rating that was newly developed specifically for BDB-infected bananas. The identity of the isolated strains was first confirmed as Blood Disease Bacterium using Sanger sequencing analysis of 16s rRNA gene. Standard biochemical tests and growth curve study showed that the BDB isolates were Gram-negative, non-motile rod-shaped, catalase-positive, oxidase-positive bacterium, and had an optimum growth rate at 35 °C. The pathogenicity of a selected virulent BDB isolate was then determined via Koch's Postulates in four local banana cultivars. Recognizing the lack of a specific disease rating scale to quantify the pathogenesis of BDB in bananas, we developed a disease rating scale specifically to BDB-infected bananas in this study. Based on the pathogenicity test, local banana cultivars (cv.) in Malaysia included cv. Berangan, cv. Nipah, cv. Awak and cv. Nangka demonstrated disease severity index (DSI) higher than 95%, indicating their susceptibility towards to BDB. In conclusion, our results showed that the four most common banana cultivars in Malaysia were highly susceptible to infection by virulent BDB. • BDB isolated from Malaysia's infected plantation was identified and characterized. • Disease rating scale was developed specifically for bananas upon BDB infection. • Local common banana cultivars in Malaysia have high susceptibility to BDB. [ABSTRACT FROM AUTHOR]