Boulbaba L’taief's research while affiliated with Centre National de Recherche des Sciences des Matériaux –CNRSM and other places

Background: Plant-growth-promoting rhizobacteria (PGPR) are a class of beneficial bacteria that colonise the roots of plants and improve projected plant growth through a multivariate process. PGPR application is increasing steadily in the field of agriculture, providing an attractive mechanism to replace pesticides, chemical fertilisers and additional supplements. Methods: In this study, PGPR from rhizospheric soil collected from Abha, a city located in the southern region of the Kingdom of Saudi Arabia (KSA), were isolated and characterised to facilitate verifying the efficacy of using PGPR as a biological control to improve fava bean growth. Four bacterial isolates from the nodules of fava bean plants, S4, S5, S6 and S17, were isolated and characterised. Consequently, an investigation highlighting the impact of PGPR isolates on the preservation of fava bean plants from the root-knot nematode was conducted through a pot culture experiment. Soil infested with the nematode was added to the pots. Two commercial types of fava bean plants (Vicia faba L.) were co-inoculated with PGPR 15 days after planting. Result: The results reveal that the nodule-forming bacteria interact synergistically; this was evidenced by a prominent increase in the shoot length and dry weight of the fava bean plants that had been cultivated in the nematode-infested soil. The results also demonstrate that the overall treatment of the plants did not lead to nodule formation. The results indicate that nodule-forming bacteria could be utilised in leguminous crops to facilitate biocontrol of the root-knot nematode.

In Tunisia, Orobanche foetida Poir. is considered an important agricultural biotic constraint on faba bean (Vicia faba L.) production. An innovative control method for managing this weed in faba bean is induced resistance through inoculation by rhizobia strains. In this study, we explored the biochemical dynamics in V. faba L. minor inoculated by rhizobia in response to O. foetida parasitism. A systemic induced resistant reaction was evaluated through an assay of peroxidase (POX), polyphenol oxidase (PPO) and phenyl alanine ammonialyase (PAL) activity and phenolic compound and hydrogen peroxide (H2O2) accumulation in faba bean plants infested with O. foetida and inoculated with rhizobia. Two rhizobia strains (Mat, Bj1) and a susceptible variety of cultivar Badi were used in a co-culture Petri dish experiment. We found that Mat inoculation significantly decreased O. foetida germination and the number of tubercles on the faba bean roots by 87% and 88%, respectively. Following Bj1 inoculation, significant decreases were only observed in O. foetida germination (62%). In addition, Mat and Bj1 inoculation induced a delay in tubercle formation (two weeks) and necrosis in the attached tubercles (12.50% and 4.16%, respectively) compared to the infested control. The resistance of V. faba to O. foetida following Mat strain inoculation was mainly associated with a relatively more efficient enzymatic antioxidative response. The antioxidant enzyme activity was enhanced following Mat inoculation of the infected faba bean plant. Indeed, increases of 45%, 67% and 86% were recorded in the POX, PPO and PAL activity, respectively. Improvements of 56% and 12% were also observed in the soluble phenolic and H2O2 contents. Regarding inoculation with the Bj1 strain, significant increases were only observed in soluble phenolic and H2O2 contents and PPO activity (especially at 45 days after inoculation) compared to the infested control. These results imply that inoculation with the rhizobia strains (especially Mat) induced resistance and could bio-protect V. faba against O. foetida parasitism by inducing systemic resistance, although complete protectionwas not achieved by rhizobia inoculation. The Mat strain could be used as a potential candidate for the development of an integrated method for controlling O. foetida parasitism in faba bean.

The intercropping system is a promising approach to augmenting the soil nutrient status and promoting sustainable crop production. However, it is not known whether intercropping improves the soil phosphorus (P) status in alluvial soils with low P under subtropical climates. Over two growing seasons––2019–2020 and 2020–2021––two experimental fields were employed to explore the effect of durum wheat (Dw) and chickpea (Cp) cropping systems on the soil available P. A randomized complete block design was used in this experiment, with three blocks each divided into three plots. Each plot was used for one of the following three treatments with three replications: Dw monocrop (Dw-MC), Cp monocrop (Cp-MC), and Dw + Cp intercrop (CpDw-InC), with bulk soil (BS) used as a control. A reduction in the rhizosphere soil pH (-0.44 and -0.11 unit) was observed in the (Cp-MC) and (CpDw-InC) treatments over BS, occurring concomitantly with a significant increase in available P in the rhizosphere soil of around 28.45% for CpDw-InC and 24.9% for Cp-MC over BS. Conversely, the rhizosphere soil pH was significantly higher (+0.12 units) in the Dw-MC treatments. In addition, intercropping enhanced the soil microbial biomass P, with strong positive correlations observed between the biomass P and available P in the Cp-MC treatment, whereas this correlation was negative in the CpDw-InC and Dw-MC treatments. These findings suggested that Cp intercropped with Dw could be a viable approach in enhancing the available P through improved pH variation and biomass P when cultivated on alluvial soil under a subtropical climate.

The use of dyes in the textile industry poses significant environmental challenges, prompting a heightened focus on physical, chemical, and electrochemical processes for wastewater treatment. This research advocates for the remediation of methyl-ene blue (MB), hydroxy naphthol blue (HNB), and trypan blue (TB) through the electro-Fenton (EF) procedure in aqueous media using iron anodes. To enhance the effectiveness of this technique, the integration of sparging air (SA) was introduced. In the EF process, the destruction of chemical oxygen demand (COD) for MB, TB, and HNB reached 89%, 89%, and 93%, respectively. With the incorporation of SA, the EF process further improved the degradation of COD for MB, TB, and HNB to 93%, 94%, and 97%, respectively. The specific electrical energy consumption (SEEC) reached 2.4, 0.8, and 1.99 kWh kg −1 COD for the 89% reduction of MB and TB and 92% reduction of HNB can be achieved through EF + SA. These results underscore the significant potential of the proposed process in treating wastewater from the textile industry. Highlights In the EF process, COD destruction for MB, TB, and HNB reached 89%, 89%, and 93%, respectively. With SA added, EF demonstrated improved COD degradation rates of 93%, 94%, and 97% for MB, TB, and HNB. SEEC measured at 2.4, 0.8, and 1.99 kWh.kg-1 COD for reducing 89% of MB and TB and 92% of HNB through EF+SA. These findings underscore the substantial capability of the suggested EF+SA process for efficiently addressing wastewater treatment in the textile industry.

Cereal–legume intercropping systems are not well studied under the semi–arid conditions of Southern Tunisia. Therefore, the present study aimed to investigate the effect of intercropping durum wheat (Triticum turgidum ssp. durum L.) with chickpea (Cicer arietinum L.) on crop grain yield and soil physicochemical proprieties such as carbon (C) and nitrogen (N) availability, microbial biomass nutrients (C and N) and plant nutrient content (N) in comparison to their monocultures. Field experiments were conducted during the 2020–2021 (EXP–A) and 2021–2022 (EXP–B) seasons in Medenine, Tunisia. The results revealed a significant augmentation (p < 0.05) in the total nitrogen proportions (Ntot) within the soil of intercropped durum wheat (DuWh–IR) compared to its monoculture (DuWh–MC). The observed variations amounted to 32% and 29% during the two growing seasons, identified as EXP–A and EXP–B. Additionally, the soil of intercropped durum wheat (DuWh–IR) significantly (p < 0.05) accumulated more total carbon (Ctot) than the monocrop (DuWh–MC) for both experiments, showing an increase of 27% in EXP–A and 24% in EXP–B. Simultaneously, the N− uptake of durum wheat significantly increased under the effect of intercropping, showing a rise of 26% in the EXP–A season and 21% in the EXP–B season. Similarly, the yield of durum wheat crops was comparatively greater in the intercropped plots as opposed to the monoculture crops, with variances of 23% in EXP–A and 20% in EXP–B. Intercropping cereals and legumes has the potential to enhance the soil fertility and crop production in the semi–arid regions of Southern Tunisia and contribute to environmental sustainability by reducing reliance on nitrogen fertilizers.

To understand how the intercropping system alleviates stressful conditions, this study was aimed at elucidating the effects of legume–cereal intercropping in enhancing phosphorus (P) availability in P-deficient soil under the semi-arid climate of southern Tunisia. During the two growing seasons––2018–2019 and 2019–2020––two experimental fields were employed to explore the effect of soil P availability on the growth of durum wheat and chickpea under different cropping systems. A randomized complete block design was used in this experiment, with three blocks each divided into three plots. Each plot was used for one of the following four cropping systems with three replications: (i) monocrop chickpea (Ck-M); (ii) monocrop durum wheat (DW-M); (iii) durum wheat–chickpea intercrop (DWCk-IC); and (iv) vacant soil without plants as a control. Compared to the vacant soil, we found a significant increase in the Olsen P concentration in the soil rhizosphere by about 16%, 48%, and 36% for the DW-M, Ck-M, and DWCk-IC, respectively. Also, the increase in soil P availability was associated with a pH decrease of −0.73 and −0.37 units for Ck-M and DWCk-IC, respectively. In addition, the soil microbial biomass P increased significantly (P < 0.05), by about 27%, 22%, and 18% for the Ck-M, DWCk-IC, and DW-M, respectively, compared to the vacant soil. The increased soil P availability improved the P contents in the durum wheat and chickpea roots and shoots, although it mostly enhanced the intercropped dry weight. These findings demonstrate that durum wheat–chickpea intercropping could be a practical cropping system for improving the soil P availability through enhanced activity in the microbial community and soil acidification.

In many African countries, drought is a major environmental stress affecting agricultural productivity. The potential solution to this problem for the common bean is to enhance its yield by the effective use of rhizobia. To improve the osmotic stress tolerance of a drought-sensitive common bean cultivar (Coco Blanc) consumed in Tunisia, plants were inoculated either with the reference strain Rhizobium tropici CIAT899 or with the local soil Rhizobium strain Ar02. Plants were grown under well-watered or medium to severe water-deficit conditions (100%, 75%, 50%, and 25% of the pot's useful reserves). Nodulation parameters measured included nodule biomass; growth (length and biomass of shoots and roots), leaf area, leaf perimeter, nitrogen content, chlorophyll and carotenoid content, soluble sugar content, and proline content were measured at the flowering stage. A significant reduction in parameters was observed due to water shortfall. However, plants inoculated with Ar02 and CIAT899 showed some tolerance to water stress; the number of nodules increased from 1 nodule/plant at 50% Useful Reserve (RU) to 28 nodules/plant at 50% RU + CIAT899. At 50% RU, the reduction in nodule biomass was 92.57% in plants inoculated with Ar02 and CIAT899 and 99.85% in control plants. Inoculation with CIAT899 increased dry biomass at 75% RU, 50% RU, and 25% RU and root length at 75% RU and 50% RU compared to the control treatment. Inoculation with CIAT899 also increased leaf area and perimeter. The effect of drought stress was lower in plants inoculated with rhizobia as demonstrated by chlorophyll a, chlorophyll b, chlorophyll a + b and carotenoid content. Rhizobia inoculation, especially with Ar02 at 50% RU and CIAT899 at 75% RU, increased nitrogen content. Inoculation also increased the soluble sugar and proline content. This study suggests that rhizobial inoculation of the common bean improves its performance and stress tolerance under adverse conditions. Key words: Rhizobia, Common bean, Nodulation, Nitrogen, Water deficit.