A novel Bacillus amyloliquefaciens BAM strain, with novel fermentation nutrient mediums and compositions, could produce potent antifungal secondary metabolites, as the existing strains face resistance from fungus pathogens. In the current study, we introduced two novel nutrient mediums for the fermentation process, semolina and peanut root extract, as carbon and nitrogen sources in order to maximize the antifungal effects of B. amyloliquefaciens against Cercaspora arachidichola to control early leaf spot disease in peanuts. Based on a single-factor test and the central composite design of response surface methodology, the optimum fermentation medium for Bacillus amyloliquefaciens antagonistic substance was determined, containing 15 gm/L of semolina flour, 12.5 gm/L of beef extract, and 0.5 gm/L of magnesium sulfate, which inhibited the fungal growth by 91%. In vitro, antagonistic activity showed that the fermentation broth of B. amyloliquefaciens BAM with the optimized medium formulation had an inhibition rate of (92.62 ± 2.07)% on the growth of C. arachidichola. Disease control effects in pot experiments show that the pre-infection spray of B. amyloliquefaciens BAM broth had significant efficiency of (92.00 ± 3.79)% in comparison to post-infection spray. B. amyloliquefaciens BAM broth significantly promoted peanut plant growth and physiological parameters and reduced the biotic stress of C. archidechola. Studies revealed that B. amyloliquefaciens BAM with a novel fermentation formulation could be an ideal biocontrol and biofertilizer agent and help in early disease management of early leaf spots in peanuts.

In the submerged fermentation process, the introduction of novel nutrient media as sources of carbon and nitrogen can enhance antifungal activity. In this study, we used a submerged fermentation process to find the optimal media for the Bacillus velezensis BP-1 strain to grow in, and that would boost its antifungal activity against Peyronellaea arachidicola. By using a single-factor test and central composite design (CCD) in the response surface methodology, the optimal fermentation medium for the B. velezensis BP-1 strain was identified. The antagonistic potential of B. velezensis BP-1 was assayed against the P. arachidicola fungus to manage web blotch disease in peanut plant leaves. The LB medium was screened as the best medium, with a maximum antifungal activity of 90% in comparison to the other mediums. Semolina flour as the carbon source, peanut root extract as the nitrogen source, and magnesium sulfate as the inorganic salt were selected as the best nutrient components in comparison to the others. The response surface methodology was optimized by using 15 g/L of semolina flour as the carbon source, 13.68 g/L of peanut root extract as the nitrogen source, and 0.50 g/L of magnesium sulfate as the inorganic salt, achieving 90% inhibition of P. arachidicola. The in vitro bioassays showed that the optimized fermentation broth of B. velezensis BP-1 had significant antifungal activity, with an inhibition rate of 88.34% against P. arachidicola. In the pot experiments on disease control, the management effects revealed that the pre-inoculation spray of the B. velezensis BP-1 broth had significant efficiency (96%) when compared to the post-inoculation spray of the B. velezensis BP-1 broth. These findings suggest that the optimized fermentation broth of the B. velezensis BP-1 strain had strong antifungal activity. This could be a potent biocontrol tool for aiding in the early disease management of web blotch in peanut plants.

Grape downy mildew (GDM) is a destructive grapevine disease caused by Plasmopara viticola that occurs worldwide. In this study, we determined the characteristics of GDM epidemics and the grapevine canopy micro-climate in open-field, fungicide-spray, and rain-shelter plots during two constitutive years (2016 and 2017). It was found that rain shelter can significantly delay the disease occurrence by 28 and 21 days, reduce the epidemic phase by 28 and 21 days, and decrease the final disease index by 82% and 83%. Furthermore, it can block precipitation, reduce the relative humidity by 11% and 8%, and reduce the leaf wetness duration by 85% and 76% compared with open-field cultivation. A total of 3861, 783, and 1145 lesions were collected from the open-field, fungicide-managed, and rain-shelter plots, respectively, for analyses of the genetic diversity, population differentiation, and epidemic mode with seven microsatellite markers. In terms of genetic diversity, the Nei’s diversity index ranged from 0.569 to 0.680 and Shannon’s information index ranged from 0.958 to 1.226, showing high levels of diversity across populations. Similar to fungicide management, a rain shelter can significantly reduce the population’s genetic diversity. Low pairwise FST values (0.003–0.047) and high gene flow (Nm = 1.548–20.699) were observed among the three populations each year. In addition, most of the genetic variation occurred within populations. The epidemic mode of GDM in the open-field, fungicide-managed, and rain-shelter cultivation showed moderate, low, and high levels of clonality, respectively, in the case study.

Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (S genes). Here, we characterized two SA hydroxylase genes (AhS5H1 and AhS5H2) as the first S genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of AhS5H1 or AhS5H2 decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each AhS5H gene increased susceptibility to Pst DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of AhS5H genes, AhNPR1 and AhPR10 was simultaneously induced by chitin. Overexpression of each AhS5H in Arabidopsis abolished the induction of AtPR1 or AtPR2 upon chitin treatment. Eventually, AhS5H2 expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of AhS5H1 and AhS5H2 was tissue-specific.

Background: Early leaf spot disease in peanut severely impacts crop yield and quality. In response, biological control by Bacillus strains offers an alternative approach to replace harmful chemical fungicides, as these bacteria produce bioactive secondary metabolites. The effectiveness of these metabolites greatly relies on the submerged fermentation process, which in turn depends on optimizing the nutrient media—especially since there is a significant difference between nutrient-optimized fermentation medium (OP) and nonoptimized fermentation medium (NOP). Results: In the present study, we isolated an antagonistic strain, Bacillus amyloliquefaciens MU-10, from soil and identified it. According to in vitro experiments, strain MU-10 exhibited potent antifungal activity against C. arachidicola , with an inhibition zone of 76 mm. Similarly, under greenhouse conditions, the disease control efficiency of the MU-10 strain against peanut leaf spot disease was 93.33%. SEM analysis revealed that the hyphae of the pathogen were destroyed and that the effect of MU-10 reduced the abundance of spores. UHPLC-MS/MS was used to elucidate the bioactive secondary metabolites produced by strain MU-10 in OP and NOP submerged fermentation. A total of 831 metabolites were detected in OP, 32% of which were classified as organic acids. Among these were 83 differentially expressed metabolites (DEMs). According to the VIP scores, 12 metabolites were identified as key contributors to group separation, including the upregulated 3-O-acetylisopimaric acid and vanillylamine. Conversely, pyrrole-2-carboxylic acid was identified as a downregulated VIP metabolite in OP. The receiver operating characteristic (ROC) curves confirmed all the metabolic results. Pure compound validation was confirmed by the use of commercially synthesized vanillylamine, pyrrole-2-carboxylic acid, and syringic acid as key antifungal agents. Conclusion: Nutrient-optimized fermentation significantly increased the production of Bacillus -based biocontrol products. This improvement represents a significant advancement in sustainable, environmentally friendly crop disease management, providing an effective solution for controlling early leaf spot in peanuts. Graphical