Screening and interaction between pathogens and antagonistic seed-borne fungi, associated with some organic spices and vegetable crops in Tunisia

Imen Ben Salem ,Yosra Abdelkhalek ,Néji Tarchoun ,Houssem Nabli ,Naima Boughalleb M’hamdi

doi:10.21608/nrmj.2019.28109

Imen Ben Salem , Yosra Abdelkhalek + Show 3 more

Open Access

https://doi.org/10.21608/nrmj.2019.28109

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Abstract

Seed-borne pathogenic and antagonistic fungi were isolated from the same organic vegetable and spice seeds (carrot, fennel, broad bean, faba bean, and lettuce), and the interaction between them were studied as a part of a biocontrol assay. In vitro dual culture assay between each pathogen and the antagonists on PDA medium was made, which led to the inhibition of the pathogens mycelial growth. According to results generated for fennel seed-borne fungi, direct confrontation of the five pathogens (Botrytis cinerea, Sclerotinia sclerotiorum, Cladosporium cladosporiodes, Cladosporium link and Bispora sp.), with Aspergillus niger and Penicillium digitatum showed an inhibition of radial growth above 50%. For lettuce; the highest inhibition was recorded by Trichoderma harzianum in confrontation with S. sclerotiorum, and P. digitatum in confrontation with Alternaria alternata. For carrot, three fungal pathogens were identified as: A. alternata, A. solani and Pythium sp., which were faced with three antagonists (P. chrysogenum, A. niger and T. harzianum), and showed radial inhibition about 50%. Concerning broad bean and baba bean; only A. alternta was isolated, and has been confronted with T. harzianum, P. digitatum, and P. italicum. During in vivo assays on fennel plant in the greenhouse; a disease severity index caused by various pathogens alone and in combination with antagonists compared to control plants, was recorded. According to results observed, fennel plants inoculated with B. cinerea and treated curatively with P. digitatum and preventively with A. niger; recorded a low disease severity index value of 0.22. This work was carried out to find effective seed-borne bioagents that could cause in vitro and in vivo inhibition of the growth of several fungal pathogens of vegetables; thus could be applied in the field for the biocontrol of fungal spice and vegetable crops diseases.

Highlights

Fungi constitute the largest group among seedborne pathogens
The most predominant fungal genera encountered on spice seeds were Aspergillus sp., Penicillium sp., Alternaria sp., and Fusarium sp
The aims of the current work were to; i)-isolate and identify seed-borne fungi from organic spices and vegetables, ii) study the in vitro and in vivo interaction between antagonists and certain fungal pathogens to detect their antifungal potentialities, could be used for biocontrol of several fungal diseases affecting these crops in the field

Summary

Introduction

Fungi constitute the largest group among seedborne pathogens. Many fungal pathogens infect the developing and maturing seeds, and reduce their yield both quantitatively and qualitatively. Seed-borne fungi can be transmitted from the seed to plants through infecting the growing seedlings (Neergaard, 1977). Detection of seed-borne fungal pathogens was important, as infected seeds often appear symptomless. Seeds treatment with beneficial microorganisms including fungi and bacteria (i.e. Trichoderma, Pseudomonas, Bacillus, Rhizobia, etc.), could improve a wide variety of biotic, abiotic, and physiological stresses to the seeds and seedlings (Mastouri et al, 2010). These bio-agents were capable of enhancing, promoting seed germination and subsequent plants growth (Moeinzadeh et al, 2010). The biocontrol efficacy of these microorganisms last longer than that of synthetic chemicals, and can protect the plant throughout all its growth stages (Rojo et al, 2007)

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