Yield of Durum Wheat Cultivar Grown under Different Nitrogen Regimes and Rainfed Conditions

The experiment was conducted in randomized complete block design with three replications in two different locations (Kef and Bousselem). The effect of four nitrogen treatments (0, 75, 100, 120 and 140 kg/ha of N) was assessed for Maali durum wheat variety on five agronomic traits: biological yield, grain yield, harvest index, 1000 kernel weight and nitrogen use efficiency. Analysis of variance revealed significant effect (P< 0.01; P< 0.001) of the nitrogen treatments for all studied traits. However, no nitrogen treatment x site interaction was noted. Except for nitrogen use efficiency, both location exhibited significant variation (p<0.01) for all the traits examined. Biological yield, grain yield, harvest index, 1000 kernel weight and nitrogen use efficiency increased with an increase in nitrogen levels. In comparison to kef site, greatest results were obtained in Bousselem site under all nitrogen levels for all measured traits. Maximum average yield (2157.27 kg/ha) and (3013.11 kg /ha) was unregistered under N4 treatment (140 kg/ha) in Kef and Boussalem site respectively. A significant and positive correlation was noted between nitrogen rates and biological yield (r = 0.74**), grain yield (r = 0.66**), harvest index (r = 0.84**) and 1000 kernel weight (r = 0.85**). In this region, it seems that the application of 140 kg/ha of N fertilization lead to great agronomic performance of Maali durum wheat variety

Progression of wheat Tan spot under different bioclimatic stages and agricultural practices

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

Assessment of Tunisian Trichoderma Isolates on Wheat Seed Germination, Seedling Growth and Fusarium Seedling Blight Suppression

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