Exploring Bacterial and Fungal Biodiversity in Eight Mediterranean Olive Orchards (Olea europaea L.) in Tunisia.

A wide array of bacteria and fungi are known for their association with pests that impact the health of the olive tree. The latter presents the most economically important cultivation in Tunisia. The microbial diversity associated with olive orchards in Tunisia remains unknown and undetermined. This study investigated microbial diversity to elucidate the microbial interactions that lead to olive disease, and the bio-prospects for potential microbial biocontrol agents associated with insect pests of economic relevance for olive cultivation in the Mediterranean area. Bacterial and fungal isolation was made from soil and olive tree pests. A total of 215 bacterial and fungal strains were randomly isolated from eight different biotopes situated in Sfax (Tunisia), with different management practices. 16S rRNA and ITS gene sequencing were used to identify the microbial community. The majority of the isolated bacteria, Staphylococcus, Bacillus, Alcaligenes, and Providencia, are typical of the olive ecosystem and the most common fungi are Penicillium, Aspergillus, and Cladosporium. The different olive orchards depicted distinct communities, and exhibited dissimilar amounts of bacteria and fungi with distinct ecological functions that could be considered as promising resources in biological control.

Identification of fungi in Tunisian olive orchards: characterization and biological control potential.

BACKGROUND: Olive production is the main agricultural activity in Tunisia. The diversity of fungi was explored in two different olive groves located in two distant geographical zones in Sfax (Tunisia) with different management practices. RESULTS: Fungal isolation was made from soil and the major olive tree pests, namely the Olive fly, Bactrocera oleae Gmelin (Diptera: Tephritidae), and the Olive psyllid, Euphyllura olivina Costa (Homoptera: Psyllidae). A total of 34 fungal isolates were identified according to their phenotypic, genotypic, biochemical and biological activities. Twenty fungal species were identified belonging to six different genera (Alternaria, Aspergillus, Cladosporium, Fusarium, Lecanicillium and Penicillium) by the analysis of their ITS1-5.8S-ITS2 ribosomal DNA region. Different bioassays performed in this work revealed that 25/34 (73.5%) of the identified fungal isolates showed an entomopathogenic and/or antagonistic activity, 9/34 (26.5%) of them displayed phytopathogenic features. CONCLUSIONS: Fungal species that showed entomopathogenic and/or antagonistic potentialities and that are non-phytopathogenic, (17/34; 50%) of our fungal isolates, could be explored for olive protection against fungal diseases and pests, and might have a future application as biocontrol agents.

Providencia entomophila sp. nov., a new bacterial species associated with major olive pests in Tunisia.

Bioprospection for potential microbial biocontrol agents associated with three major insect pests of economic relevance for olive cultivation in the Mediterranean area, namely the olive fly, Bactrocera oleae, the olive moth, Prays oleae, and the olive psyllid, Euphyllura olivina, led to the isolation of several strains of readily cultivable Gram-negative, rod-shaped bacteria from Tunisian olive orchards. Determination of 16S ribosomal RNA encoding sequences identified the bacteria as members of the taxonomic genus Providencia (Enterobacterales; Morganellaceae). A more detailed molecular taxonomic analysis based on a previously established set of protein-encoding marker genes together with DNA-DNA hybridization and metabolic profiling studies led to the conclusion that the new isolates should be organized in a new species within this genus. With reference to their original insect association, the designation "Providencia entomophila" is proposed here for this hypothetical new taxon.

Strategies to Fight Hidden Hunger in Ethiopia, Egypt, Sudan and Tunisia.

The four countries, Ethiopia, Egypt, Sudan, and Tunisia, face different nutrition challenges and have different experiences and policies in place to combat hunger. Stunting rates among children below 5 years are highest in Ethiopia and Sudan (38%) compared to Sudan and Tunisia (21 and 11-9%). Children below 5 years in Egypt and Tunisia also suffer from higher risks to become overweight and obese; 14-16% are considered overweight. Food security is limited in all countries, especially in Sudan. All four countries have nutrition and/or poverty alleviation policies in place but implementation is challenging or very weak to realize the plan. However, some successes are observed. The authors recommend that to solve the malnutrition problems in the countries: (1) implementation of the respective policies has to be given better attention than writing and approval of it, (2) it is important to consider the country-specific comparative advantage of livestock production, (3) cultivation of nutritious crops for any level of rural and urban population, and (4) and nutrition has to be put on top of the national agenda like food security. Furthermore, both national and international concerning organizations should support these countries to build their capacity in terms of technical skills and technological options.