Considera

Isolation of entomopathogenic Bacillus from a biodynamic olive farm and their pathogenicity to lepidopteran and coleopteran insect pests

Imen Blibech, Mohieddine Ksantini, Ikbal Chaieb, Brahim Jlassi, Ali Rhouma, Samir Jaoua, Sami Aifa

Abstract
The occurrence of Bacillus entomopathogenic bacteria on a Tunisian biodynamic farm was determined by examining 75 samples from olive tree (Olea europaea L.) habitats. A total of 40 Bacillus isolates were characterized according to their phenotypic, physiological and biochemical parameters. Isolates of the species Bacillus subtilis, Bacillus mycoides, Brevibacillus brevis, Paenibacillus polymyxa, Bacillus licheniformis, Bacillus sp. (1), Bacillus sp. (2) and a standard strain Btk HD-1 were used separately in feeding bioassays on fresh artificial diet against larvae of lepidopterans Prays oleae (Bernard) and Palpita unionalis (Hübner) and coleopterans Hylesinus oleiperda (F.) and Phloeotribus scarabaeoides (Bernard), which are olive tree pests. Larvae were successfully reared on an artificial diet with 25 g powdered olive tree leaves. Compared to the control data, only Btk and the isolates of B. licheniformis, P. polymyxa and B. brevis were entomopathogenic. Larval mortality assessed 7 days post-treatment showed high mortality rates with Btk to lepidopteran larvae (86.6% for P. oleae and 80.9% for P. unionalis) and low mortality against coleopteran pests. B. brevis isolates showed high mortality rates against P. oleae (up to 67.9%). B. licheniformis isolates caused up to 59.2% larval mortality for P. oleae and 43.6% for P. unionalis. Highest coleopteran mortality was achieved by P. polymyxa isolates (up to 55%). According to the 16S rDNA results, isolates of each of the three entomopathogenic strains were similar. Proteins in the strain supernatants were toxic to P. oleae larvae with LC50 values of 10.0 (B. brevis), 12.5 (B. licheniformis) and 37.6 μg/ml (P. polymyxa). Also, P. polymyxa showed an LC50 of 12.4 mg/l against P. scarabaeoides. Our results suggest that entomopathogenic Bacillus present locally in the biodynamic farm could be used in biological control programmes of olive tree pests.

Highlights
► 40 Bacillus spp. were isolated from samples of olive tree habitats on a Tunisian biodynamic farm. ► Entomopathogenic species were characterized and insecticidal bioassays were realized. ► Btk and B. brevis show most activity to lepidopteran. ► P. polymyxa show most activity to coleopteran. ► Locally isolated Bacillus strains showed potential for biological control.

A related paper from the team

Sustainable Configuration of the Tunisian Olive Oil Supply Chain Using a Fuzzy TOPSIS-Based Approach

Ahlem Jellali, Wafik Hachicha , and Awad M. Aljuaid

Abstract: Agricultural production of olive oil is a sector with high significance. The olive sector is a
very important sector for several countries in the world, in particular, for Tunisia. In addition, the
impacts of olive oil production and extraction on economic, environmental, and social issues are
considerable. The main objective of this work is to propose a better configuration of the Tunisian olive
oil supply chain (OOSC) from a sustainable development (SD) perspective. The proposed approach
consists of applying a fuzzy technique for order preference by similarity to ideal solution (TOPSIS)
method as a multi-criteria approach. The proposed approach is applied twice. In the first application,
the objective is to compare five possible scenarios for the olive agricultural phase. In the second
application, the objective is to compare three possible scenarios for the olive oil transformation phase.
The major findings of this research include the following: (1) The best scenario for the agricultural
phase is the intensified organic system, which is based on biodynamic olive growing. (2) The best
scenario for the transformation phase (oil extraction) is the continuous two-phase extraction system.
Consequently, the efficient way for the by-products processing phase is the use of wet pomace for the
preparation of biodynamic compost.

Keywords: sustainable development; olive oil supply chain; performance evaluation; multi-criteria
decision analysis; fuzzy TOPSIS; agricultural phase; transformation phase; by-products processing
phase