Abstract
Fusarium wilt is an economically important disease of cucumber caused by the fungus Fusarium oxysporum f. sp. cucumerinum (Foc). It causes severe losses in the yield and quality of cucumber and is extremely difficult to control conventionally using chemical fungicides. Biological control offers an eco-friendly alternative to chemical pesticide for sustainable plant disease management. In this context, biocontrol activity of rhizosphere soil bacteria was investigated against Foc in vitro. Thirty-five rhizobacterial isolates were screened for antagonistic activity in dual culture, and isolate BA5 showed the highest antagonistic activity (58.33% mycelial growth inhibition) against Foc. Maximum fungal biomass reduction (90.20%) was found in King’s B broth in shake flask culture. Cell-free culture filtrate and ethyl acetate crude extract inhibited mycelial growth of Foc by 56.66 and 25.0%, respectively. Further, the selected isolate produced siderophores, volatile compound(s), hydrocyanic acid, and protease. Siderophores and volatile compound(s) were involved in the isolate-induced antagonism. In addition, the isolate exhibited several plant growth-promoting traits, including phosphate and zinc solubilization, ammonia production, organic acid production, and in vitro biofilm formation. Based on the morphological, physiological, biochemical characteristics, and phylogeny analysis, the isolate BA5 was identified as Pseudomonas aeruginosa, and the 16S rDNA sequence was submitted in the NCBI GenBank under the strain name RKA5. Because of the novel antifungal and plant growth promotion potentials, the strain can be used as a promising biocontrol agent against the fungal pathogen Foc.
Highlights
Plant diseases account for ~ 13% of the world’s crop production lost, nearly equivalent to $220 billion lost every year (Kandel et al 2017)
Isolation of rhizobacterial strains Six soil samples were collected from the rhizosphere of five different crop/vegetable plants, namely mustard (Brassica campestris), pea (Pisum sativum), bathua (Chenopodium album), lentil (Lens culinaris), and radish (Raphanus sativus), grown in agricultural fields located near the Islamic University, Kushtia, Bangladesh
Mass screening for antagonistic activity A total of 35 bacterial isolates were obtained from rhizosphere soils of five different crop/vegetable plants by serial dilution technique
Summary
Plant diseases account for ~ 13% of the world’s crop production lost, nearly equivalent to $220 billion lost every year (Kandel et al 2017). For example, is an important fungal pathogen known to cause vascular wilt diseases in more than 100 different species (Lopez-Berges et al 2012). Cucumerinum (Foc), a soil-borne pathogen, is the causal agent of vascular wilt disease in cucumber and causes significant yield loss (Al-Tuwaijri 2015). The visible symptoms of the disease include necrotic lesions, followed by foliar yellowing, wilting, vascular tissue damage, and plant death (Ahmed 2010). It can grow along the xylem vessel in plant tissues and survive in soil as chlamydospores or saprophytes over a year (Yang et al 2014), making it extremely difficult to control
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