Potential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria

Abstract

Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control approach that has shown its great potential as an efficient eco-friendly alternative to treating root rot diseases. In the present study, the antagonistic activity of ten bacterial isolates was tested both in vitro and in planta against Pythium schmitthenneri, the causal agent of olive root rot disease. These bacterial isolates belonging to the genera Alcaligenes, Pantoea, Bacillus, Sphingobacterium, and Stenotrophomonas were chosen for their potential antimicrobial effects against many pathogens. Results of the in vitro confrontation bioassay revealed a high reduction of mycelial growth exceeding 80%. The antifungal effect of the volatile organic compounds (VOCs) was observed for all the isolates, with mycelial inhibition rates ranging from 28.37 to 70.32%. Likewise, the bacterial cell-free filtrates showed important inhibition of the mycelial growth of the pathogen. Overall, their efficacy was substantially affected by the nature of the bacterial strains and their modes of action. A greenhouse test was then carried out to validate the in vitro results. Interestingly, two bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14, were the most successful in managing the disease. Our findings suggested that these two antagonistic bacterial isolates have promising potential as biocontrol agents of olive root rot disease.

Screening of Rhizobacterial Isolates from Apple Rhizosphere for Their Biocontrol and Plant Growth Promotion Activity

“…and the bacterial isolates Serratia odorifera and Pseudomonas fluorescens, the results revealed the ability of these bacterial species to inhibit the mycelial growth of the mentioned fungal pathogens [57]. The Bacillus genus has been extensively employed as a microbial biopesticide to its high inhibitory effect on mycelial growth in many studies [31,[58][59][60][61]. A study conducted by Liu et al [62] demonstrated that using Bacillus amyloliquefaciens, B. velezensis, B. siamensis, B. subtilis, and B. atrophaeus as a composite microbial culture resulted in a significant reduction in the abundance of Fusarium sp.…”

“…Bacteria, particularly those belonging to the genera Bacillus, Pseudomonas, and Enterobacter, have demonstrated their potential as biological control agents against various plant pathogens, including P. vexans [26][27][28][29]. These bacteria can inhibit the growth and development of phytopathogens by producing antibiotics, lytic enzymes, and siderophores that deprive the pathogen of essential resources or directly lyse its cells [30][31][32]. In addition to their antagonistic activity, some bacteria-namely, PGPR-possess plant growth-promoting properties that can improve plant vigor and productivity [33,34].…”

Confronting stresses affecting olive cultivation from the holobiont perspective

“…Measures such as crop rotation, soil solarization, and mostly the use of fungicides, have been implemented to control these pathogens. Recently, effectiveness of Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14 to manage olive root rot caused by P. schmitthenneri was reported (Legrifi et al, 2022a).…”

The Hidden World within Plants 2.0

“…Additionally, the bacterial cell-free filtrates also demonstrated a significant inhibition of the pathogen mycelial growth. To validate their findings obtained in vitro, Legrifi et al [4] conducted greenhouse tests. Among the bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14 emerged as the most successful in controlling the severity of olive root rot disease.…”

“…In their study, Legrifi et al [4] focused on evaluating the potential of ten bacterial strains, isolated from the rhizosphere of citrus and blossoms of pear, apple, and quince trees, for their ability to suppress the mycelial growth of Pythium schmitthenneri, a pathogenic agent causing root rot disease in olive trees. These bacterial strains belonging to the genera Alcaligenes, Bacillus, Pantoea, Sphingobacterium, and Stenotrophomonas, were selected for their antagonistic properties against various pathogens [5].…”