Biological Control of Stem Canker and Black Scurf on Potato by Date Palm Compost and its Associated Fungi

• Published in: Journal of phytopathology Vol. 164; no. 1; pp. 40 - 51
• Main Authors: El Khaldi, Rabeb, Daami-Remadi, Majda, Cherif, Mohamed
• Format: Journal Article
• Language: English
• Published: Berlin Parey 2016; Blackwell Publishing Ltd; Wiley Subscription Services, Inc
• Subjects: compost-borne fungi; disease incidence; disease severity index; plant growth; Rhizoctonia solani; Solanum tuberosum
• ISSN: 0931-1785; 1439-0434
• DOI: 10.1111/jph.12423

The suppressive effects of two different types of date palm composts and some of their indigenous microorganisms were evaluated in vitro and on potato plants inoculated with Rhizoctonia solani. Fungi isolated from composts screened against R. solani by dual cultural assays on PDA showed a significant inhibition of pathogen mycelium growth as compared with untreated control. The type of hyphal interactions between R. solani and each tested antagonist was observed by light microscopy. Microscopic observations carried out at the confrontation zone of both agents showed different mechanisms of actions: mycelia lyses, mycoparasitism and/or formation of mycelia cords via anatomosis between mycelia filaments. Unsterilized and sterilized compost extracts were tested for efficacy against R. solani using agar‐well diffusion method or by pouring the extracts on PDA. Two sterilization methods were used: a filtration through a microfilter of 0.22 microns or autoclaving. Results showed that compost extract lost its activity after heating or filtration, confirming that chemical factors in compost had no direct inhibiting effect on the pathogen. The suppressiveness of composts was mainly due to their biotic component. Series of greenhouse trials showed that black scurf and stem canker incidence and severity were significantly reduced in peat–sand amended with compost compared with the untreated control. However, the potential suppressive effect of cattle manure and date palm compost (CMC) was higher than sheep manure and date palm compost (SMC). On potato seed tubers pre‐inoculated with the selected fungal isolates from compost, there was variability in the reduction of disease severity among treatments. Plant growth was unaffected by the application of fungal antagonists or by CMC amendment; however, an increase in the total yield was observed by the SMC potting mix compared with untreated control.