In vivo and In vitro evaluation of the antifungal activity of the PGPR Bacillus amyloliquefaciens RaSh1 (MZ945930) against Alternaria alternata with growth promotion influences on Capsicum annuum L. plants

Abstract

Alternaria alternata that threatens pepper production and causes major economic harm is responsible for the leaf spot/blight disease. Chemical fungicides have been widely employed; unfortunately, fungicidal resistance is a current concern. Therefore, finding new environmentally friendly biocontrol agents is a future challenge. One of these friendly solutions is the use of bacterial endophytes that have been identified as a source of bioactive compounds. The current study investigates the in vivo and in vitro fungicidal potential of Bacillus amyloliquefaciens RaSh1 (MZ945930) against pathogenic A. alternata. In vitro, the results revealed that RaSh1 exhibited strong antagonistic activity against A. alternata. In addition to this, we inoculated pepper (Capsicum annuum L.) plants with B. amyloliquefaciens RaSh1 and infected them with A. alternata. As a result of A. alternata infection, which generated the highest leaf spot disease incidence (DI), the plant's growth indices and physio-biochemical characteristics significantly decreased, according to our findings. Our results also showed the abnormal and deformed cell structure using light and electron microscopy of A. alternata-infected leaves compared with other treatments. However, DI was greatly reduced with B. amyloliquefaciens RaSh1 application (40%) compared to pepper plants infected with A. alternata (80%), and this led to the largest increases in all identified physio-biochemical parameters, including the activity of the defense-related enzymes. Moreover, inoculation of pepper plants with B. amyloliquefaciens RaSh1 decreased electrolyte leakage by 19.53% and MDA content by 38.60% as compared to A. alternata infected ones. Our results show that the endophyte B. amyloliquefaciens RaSh1 has excellent potential as a biocontrol agent and positively affects pepper plant growth.

Attenuation of Zucchini mosaic virus disease in cucumber plants by mycorrhizal symbiosis

“…It is significant to note that ROS have a dual function in inducing pathogen limitation and frequently localized death of host plant cells at the infection sites, as well as acting as a diffusible signal that triggers antioxidant and pathogenesis-related defense responses in surrounding plant cells (Hernández et al 2016 ). So, a further experiment was conducted to better appreciate the oxidative damage through lipid peroxidation analysis as one of the biomarkers for oxidative stress measured by malondialdehyde (MDA) content (Abdelhameed et al 2021b ; Abdalla et al 2022 ; Soliman et al 2023 ). In the present work, ZYMV-infected cucumber plants accumulated more MDA (16.096 nmol/g fw) than healthy plants (11.387 nmol/g fw) (Fig.…”

“…6 b and c). As soon as plants are exposed to microbial pathogens, they release ROS that cause programmed cell death in the plant cells near the infection site, thereby fencing off the pathogen and stopping the disease process (Hamzah et al 2021 ; Soliman et al 2023 ). The amino acid proline functions as a powerful ROS scavenger, redox balancer, molecular chaperon, and protein structural stabilizer, which may inhibit the triggering of programmed cell death by ROS (Chen and Dickman 2005 ; Soni et al 2022 ).…”

Plant-Growth-Promoting Rhizobacteria Modulate Carbohydrate Metabolism in Connection with Host Plant Defense Mechanism

“…Upon being challenged by an attacker, plants receive PGPR warning signals and thus could display an enhanced perception of the attacker and mount a faster and stronger immune response [62,64]. In addition to priming plants' defense responses against pathogens, certain PGPR strains are helpful for maintaining photosynthesis and even enhancing its capacity and efficiency [65][66][67]. Mitigating damage to photosynthesis and the energy loss caused by pathogen invasion or plant defense ensures plant growth in the face of stress.…”

“…Pepper leaf infection by the necrotrophic fungus Alternaria alternata significantly reduced photosynthetic pigments and chloroplasts, collapsed chloroplasts, and changed photosynthetic chemistry [67]. Significant photosynthetic pigment loss commonly results from pathogen infection and manifests as chlorosis [68][69][70].…”

“…During common bean plant infection by the hemibiotrophic pathogen Colletotrichum lindemuthianum, the photosynthetic rate was linearly correlated with total Chl and carotenoid contents [68]. Soliman et al [67] employed B. amyloliquefaciens RaSh1 as a biocontrol agent against A. alternata on pepper plants. B. amyloliquefaciens RaSh1 root inoculation increased Chl a and b and carotenoids levels and promoted plant growth, regardless of whether or not the plants were infected with A. alternata.…”