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Tan spot, caused by Pyrenophora tritici-repentis, is a severe worldwide wheat foliar disease and has become common in Tunisia. Two hundred wheat field surveys were conducted in northern Tunisia during the 2017-2019 seasons to determine disease intensity and the correlation of the tan spot with agricultural practices and environmental factors. The disease infested 67% of the visited regions. The highest prevalence (87.5%), incidence (> 30%), and severity (> 10%) were observed in sub-humid regions, contrary to the middle semi-arid regions. Logistic regression was used to analyse the correlation of incidence and severity with various factors as independent variables. In a multiple variable model, the bioclimatic stages, variety, previous crop, humidity, and rainfall were significantly associated with tan spot incidence and severity. High incidence and severity were significantly correlated to the sub-humid regions, varieties Maâli, Razzak, Karim, and Carioca, rainfall, high level of humidity, and monoculture. The correlation between the tan spot and several environmental factors must be considered to ensure successful and sustainable disease management strategies. [ABSTRACT FROM AUTHOR]

Beneficial microorganisms, including members of the Trichoderma genus, are known for their ability to promote plant growth and disease resistance, as well as being alternatives to synthetic inputs in agriculture. In this study, 111 Trichoderma strains were isolated from the rhizospheric soil of Florence Aurore, an ancient wheat variety that was cultivated in an organic farming system in Tunisia. A preliminary ITS analysis allowed us to cluster these 111 isolates into three main groups, T. harzianum (74 isolates), T. lixii (16 isolates) and T. sp. (21 isolates), represented by six different species. Their multi-locus analysis (tef1, translation elongation factor 1; rpb2, RNA polymerase B) identified three T. afroharzianum, one T. lixii, one T. atrobrunneum and one T. lentinulae species. These six new strains were selected to determine their suitability as plant growth promoters (PGP) and biocontrol agents (BCA) against Fusarium seedling blight disease (FSB) in wheat caused by Fusarium culmorum. All of the strains exhibited PGP abilities correlated to ammonia and indole-like compound production. In terms of biocontrol activity, all of the strains inhibited the development of F. culmorum in vitro, which is linked to the production of lytic enzymes, as well as diffusible and volatile organic compounds. An in planta assay was carried out on the seeds of a Tunisian modern wheat variety (Khiar) by coating them with Trichoderma. A significant increase in biomass was observed, which is associated with increased chlorophyll and nitrogen. An FSB bioprotective effect was confirmed for all strains (with Th01 being the most effective) by suppressing morbid symptoms in germinated seeds and seedlings, as well as by limiting F. culmorum aggressiveness on overall plant growth. Plant transcriptome analysis revealed that the isolates triggered several SA- and JA-dependent defense-encoding genes involved in F. culmorum resistance in the roots and leaves of three-week-old seedlings. This finding makes these strains very promising in promoting growth and controlling FSB disease in modern wheat varieties. [ABSTRACT FROM AUTHOR]

Sixty-three isolates of Pyrenophora tritici-repentis collected from various wheat areas of the north of Tunisia were characterized and studied for their variability. Under in vitro conditions, morpho-cultural characterization showed the presence of several colors of colonies. An inoculation bioassay was performed identifying the presence of three symptoms type i.e., small brown spots, chlorosis, and necrosis with chlorosis. ANOVA of leaf infected area and lesion length data caused by isolates showed significant difference, and Ascending Hierarchical Clustering discriminated them into two distinct pathogenic profiles. Molecular detection of virulence effector genes demonstrated the presence of ToxA, ToxB, and toxb gene individually or in combination, resulting in five different gene profiles. These results indicate large variability of features. Multiple Correspondence Analysis and Ascending Hierarchical Clustering identified four distinct isolates classes. Both pathogenic profiles of isolates appeared in all the groups. Hence, it was not possible to establish a relationship between variability characters and geographical regions from which the isolates were collected. [ABSTRACT FROM AUTHOR]

Background: Drought is a major problem limiting the growth and development of plants in the world and especially in Tunisia. Halophytes constitute a renewable wealth and they offer great flexibility with regard to abiotic stresses, and they are evaluated for their ecological and potential food use. Results: The proposed work identifies the response of Atriplex hortensis var. rubra to the germinal stage and the reproductive stage under a deficient water regime to measure the drought resistance of this plant that has very interesting forage production abilities. The morphological and water parameters are used to characterize the physiological response of this species to the effects of water deficit. For the germination test, four levels of osmotic potential caused by PEG-6000 solutions at different levels of water potential (− 0.1, − 0.5, − 1.0, − 1.5 MPa) were adopted in seed of A. hortensis germination media. The methodology adopted in the second experiment is based on the cultivation of potted plants stored in a semi-controlled greenhouse at flowering stage. The water deficit was imposed on the plants by watering stop for a week, and the control plants are subjected to a water regime maintained irrigated at 100% of the capacity in the field. Drought tolerance was scored 30 days after the drought stress commenced based on the number of branches and leaf, dry biomass, relative water content, leaf water potential, and nitrogen content. No significant difference was observed in germination rates for all PEG concentrations throughout the experiment which are still close to 60%. The results obtained for the second experiment show a high tolerance of A. hortensis under water stress. Drought induced decreases in two physiological parameters, the number of branches and leafs, and the relative water content of annual Atriplex. Heatmap and PCA data revealed that physiological parameters are more sensitive than morphological parameters in distinguishing the control and drought treatments. Conclusions: Indeed, the orache is distinguished by a great ability to retain water potential after a month of stress. Thus, height, number of branches, leaf and shoot dry weight, and percentage of nitrogen were significantly similar for controls and stressed for A. hortensis. On the other hand, measured root length and basic and midday water potential show significant variability between controls and stressors. In addition, these results highlight the importance of the resistance of Atriplex halophyte forage to drought. [ABSTRACT FROM AUTHOR]

Ascochyta blight of faba bean, caused by Ascochyta fabae, is one of the most destructive diseases of faba bean (Vicia faba) in Tunisia. Yield losses caused by the disease can reach 35% under conditions favourable for disease development. Despite its widespread occurrence, only the asexual part of Ascochyta life-cycle has been recovered in Tunisia. However, the sexual stage of the fungus is suspected to play an important role in the epidemiology of the disease, given the distribution of the primary infection symptoms. Pseudothecia of Didymella fabae, the teleomorph of A. fabae, were first observed in autumn-winter 2010-2011, on faba bean debris collected from the region of Beja (Tunisia) and placed in three different locations. Mature pseudothecia were first observed 2 months after the debris placement, with the typical characteristics of Didymella fabae. Isolation from ascospores resulted in typical cultures of A. fabae which produced typical symptoms of the disease when used to inoculate faba bean seedlings. This is the first report of D. fabae in Tunisia. The occurrence of the teleomorph has important implications for epidemiology of Ascochyta blight and therefore, on its management in faba bean crops. [ABSTRACT FROM AUTHOR]

The implementation of conservation agriculture (CA) remains crucial for facing interannual variability in climatic conditions that impact durum wheat production and food security. The current work was conducted to assess the effects of the tillage practice, previous crop, and nitrogen (N) fertilization rate on the agronomic and economic performances of rainfed durum wheat in a semi-arid environment in Tunisia. Tillage practices included no-tillage (NT) and conventional tillage (CT). Preceding crops were either a common vetch or a bread wheat. The N rates applied were: 0, 75, 100, 120, and 140 kg N ha−1. Our results show that, based on a 2-year experiment, tillage practices are not affecting grain yield, grain N, and gross margins. However, the N-use efficiency of durum wheat was significantly higher when wheat was grown using NT. Grain yield and N content in grain were 340 kg ha−1 and 0.34%; much higher after vetch than after bread wheat. For both tillage practices, the merit of 75 kg N ha−1 is paramount to maximize yield through a more efficient use of available N. Our results highlight the importance of no-tillage-based CA combined with rotation, including vetch, on enhanced yields, N-use efficiency, and gross margins. These findings provide the evidence of the positive impact of CA for rainfed durum wheat under semi-arid Mediterranean conditions. [ABSTRACT FROM AUTHOR]