Abstract
BackgroundBlack root rot of strawberry plants caused by Rhizoctonia solani, Fusarium solani, and Pythium sp. is a serious disease in Egypt. Biocontrol agents have frequently proved to possess paramount and safe tools against many diseases. The impact of soil treatments with 3 Bacillus pumilus isolates on black root rot disease of strawberry plants caused by R. solani, F., and Pythium sp. under laboratory and field conditions was examined herein on the commonly used ‘Festival’ strawberry cultivar. To increase the bacterial adhesion and distribution on the roots, each seedling was dipped in bacterial cell suspension at 1 × 108 colony-forming units/ml of each separate bacterial isolate for 30 min then mixed with 5% Arabic gum.ResultsThe tested B. pumilus isolates significantly reduced the growth area of these 3 fungi. The two bacterial isolates Nos. 2 and 3 reduced the growth area by more than 85.2, 83.6, and 89.0% for R. solani, F. solani, and Pythium sp., respectively. Likewise, the 3 bacterial isolates significantly (P ≤ 0.05) inhibited the disease under field conditions. Isolates Nos. 2 and 3 suppressed the disease incidence by 64.4 and 68.9% and disease severity by 65.3 and 67.3%, respectively. The fungicide Actamyl had effect similar to that of the 2 isolates. B. pumilus isolates significantly enhanced growth parameters and yields of strawberry plants; isolates Nos. 2 and 3 raised the yield by 66.7 and 73.3%, respectively.ConclusionsBacillus pumilus isolates could effectively manage the black rot disease in strawberry herein. Due to the significant impact of the root rot disease on strawberry yield, B. pumilus should be further tested to manage the disease on strawberry on large scale in Egypt.
Highlights
Black root rot of strawberry plants caused by Rhizoctonia solani, Fusarium solani, and Pythium sp. is a serious disease in Egypt
The strawberry cultivar Festival was dipped in bacterial cell suspension at concentration of 1 × 108 colonyforming units (CFU)/ml of each separate bacterial isolate for 30 min mixed with 5% Arabic gum to enhance adhesive capacity and perfect distribution of the bioagent on the outer parts of the treated roots just before transplanting
The highest decrease was obtained with the isolates Nos. 2 and 3, which inhibited the growth by more than 83.6, 85.2, and 89% for F. solani, R. solani, and Pythium sp., respectively
Summary
Black root rot of strawberry plants caused by Rhizoctonia solani, Fusarium solani, and Pythium sp. is a serious disease in Egypt. The impact of soil treatments with 3 Bacillus pumilus isolates on black root rot disease of strawberry plants caused by R. solani, F., and Pythium sp. Methyl bromide (MB) alone or in combination with other pesticides has been effectively utilized as a preplant fumigant to suppress many soil-borne pathogens, weeds, and PPNs in Egyptian strawberry fields (AbdElgawad 2019) This fumigant has recently been banned worldwide for almost all cultivated crops including strawberry due to its hazardous residues (Noling 2016). Biocontrol agents included several Bacillus spp., which could suppress the causal pathogens and increase the yields of the treated plant species One such rod-shaped endospore-forming, Gram-positive, aerobic bacteria of the genus Bacillus is B. pumilus. Each of two tested B. pumilus strains has demonstrated distinguishable toxins between them (Hoult and Tuxford 1991). Mahmoud et al (2006) appraised Pseudomonas fluorescens and several Bacillus species as they showed a remarkable efficacy against several pathogenic fungi such as F. solani and R. solani on peanut roots
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