Antagonistic Activity against Dirty Panicle Rice Fungal Pathogens and Plant Growth-Promoting Activity of Bacillus amyloliquefaciens BAS23

Abstract

Bacterial strain BAS23 was isolated from rice field soil and identified as Bacillus amyloliquefaciens. Based on dual culture method results, the bacterium BAS23 exhibited potent in vitro inhibitory activity on mycelial growth against a broad range of dirty panicle fungal pathogens of rice (Curvularia lunata, Fusarium semitectum and Helminthosporium oryzae). Cellfree culture of BAS23 displayed a significant effect on germ tube elongation and mycelial growth. The highest dry weight reduction (%) values of C. lunata, H. oryzae and F. semitectum were 92.7%, 75.7%, and 68.9%, respectively. Analysis of electrospray ionization-mass spectrometry (ESI-MS) and 1 H nuclear magnetic resonance (NMR) spectroscopy revealed that the lipopeptides were iturin A with a C14 side chain (C14 iturinic acid), and a C15 side chain (C15 iturinic acid), which were produced by BAS23 when it was cultured in nutrient broth (NB) for 72 h at 30°C. BAS23, the efficient antagonistic bacterium, also possessed in vitro multiple traits for plant growth promotion and improved rice seedling growth. The results indicated that BAS23 represents a useful option either for biocontrol or as a plant growthpromoting agent.

Efficacy of fungicides in controlling rice blast and dirty panicle diseases in Thailand

“…Biological control agents viz. Trichoderma, Talaromyces, and Bacillus against this disease have been reported in Thailand 6,26,29 . In the current study, the combined fungicides of triazole and fluopyram + tebuconazole demonstrated dirty panicle disease suppression of up to 60% when applied twice, while two applications of the strobilurin fungicide, azoxystrobin, reduced the incidence of the disease by 56% in 2016, a year of heavy rainfall.…”

“…Mancozeb is an effective fungicide which carries out the protective activity of inhibiting spore germination but only on leaf surfaces 27 . Rainfall may have lowered mancozeb's fungicidal activity against rice diseases in field trials 28,29 .…”

“…Dirty panicle or seed discoloration is a serious rice disease in Thailand. This disease has shown greater severity under conditions of high rainfall and humidity 29 , evidenced by the disease's higher incidence in 2016 than in 2017. Biological control agents viz.…”

The Mode of Action of Bacillus Species against Fusarium graminearum, Tools for Investigation, and Future Prospects

“…Detection is done using techniques such as liquid chromatography–mass spectrometry (LC–MS). Examples of these studies are those which were conducted to detect and/or analyze surfactin, fengycin, and iturin produced by Bacillus against various plant pathogenic fungi [77,100,101,102,103,104,105,106,107]. Two initial scenarios may require this type of testing.…”

Linking soil's volatilome to microbes and plant roots highlights the importance of microbes as emitters of belowground volatile signals

“…Bacteria are another important component of the plant root microbiome that plays a key role in plant nutrition, root development and plant health. Some bacterial strains enhance nutrient acquisition in plants (Nissinen et al, 2012;Bulgarelli et al, 2013;Vandenkoornhuyse et al, 2015;Kielak et al, 2016), support stress adaptation (Vandenkoornhuyse et al, 2015) or, like Bacillus amyloliquefaciens, suppress plant pathogens (Santhanam et al, 2015;Gómez Expósito et al, 2017;Saechow et al, 2018). Others can have deleterious or no visible effects on plants (Mansfield et al, 2012).…”