Stripe rust caused by Puccinia striiformis, is currently the major foliar disease of spring bread wheat (Triticum aestivum L.) in Tunisia, causing serious yield losses and affecting grain quality. Farmers often use foliar fungicide application or resistant cultivars to counter yield loss, however, this is hampered by a lack of resistant varieties. To investigate the effects of genetic resistance and foliar fungicide application on disease level and yield components, six improved varieties were evaluated at the regional experimental station in Beja during three consecutive growing seasons. Under natural stripe rust infection, three varieties were detected as completely resistant and the others are susceptible. The pathogen affected the leaf area in the susceptible varieties and reduces the above ground biomass at harvest, seed weight and grain yield. Fungicide application reduces the disease severity on the sensitive genotypes and improves biomass, seed weight, grain yield, and harvest index. Yield benefits were much greater in the use of resistant genotypes than fungicide application on the susceptible varieties; consequently the resistance to stripe rust can have more significant benefits to farmer and to the wheat industry.
Introduction: Stability and adaptability of 25 bread wheat (Triticum aestivum L.) cultivars were evaluated for genotype × environment interaction (G × E) and yield stability across two environments over 2 years (2014 and 2015). Materials and methods: Five improved varieties (Haidra, Salammbô, Tahent, Utique, and Vagua) released in Tunisia and 20 introduced genotypes (V1-V20) have been tested under two contrasted environments during 2 years characterized by different precipitations in the northwest of Tunisia. Several statistical approaches were conducted to evaluate yield stability: (a) regression coefficient (b i ), (b) deviation from regression (S di ), (c) ecovalence (W i ), (d) Hühn stability (S li ), and (e) AMMI stability value. Results: A standard multifactor analysis of variance test showed that the main effects due to genotypes, locations, and the interaction (genotype × locations) were highly significant. The highly significant interactions indicate that genotypes need to be tested during several years and at different locations for selecting the most stable one. The results showed that all statistical analyses allowed classifying the 25 studied genotypes according to their grain yield level (low, medium, or high), their adaptability to different environments. Conclusion: Tahent variety was confirmed to be most valuable due to its high production level, stability and its adaptability to variable environments including unfavorable ones.
Phenotyping for quantitative resistance to Septoria tritici blotch (STB), one of the most economically devastating diseases of durum wheat (Triticum durum Desf.) in North African region, is a limiting factor for breeding progress. Here we tested main phenotypic markers of aggressiveness affecting host damage and pathogen reproduction reported in earlier studies for measuring differences in quantitative host resistance. A collection of 11 Tunisian durum wheat genotypes varying in resistance to the pathogen was inoculated by a highly aggressive and virulent isolate of Zymoseptoria tritici in a replicated field and controlled experiments, conducted in 2017-2018 at the experimental station of the Regional Field Crops Research Center of Beja in Tunisia. The severity of infection caused by Z. tritici isolate, including percentage of leaf area covered by chlorotic lesions (PLACCL), percentage of leaf area covered by necrosis (PLACN), and percentage of leaf area covered by pycnidia (PLACP) as well as latent period (LP) and pycnidia density (PYC dens ) were assessed visually and quantified. The results showed that there were significant differences in all assessed traits on the tested genotypes and significant positive correlations were obtained between PLACN, PLACP and PYC dens . Similarly, there was a significant negative correlation between LP and these last traits. The PLACP was found as the more reliable trait to discriminate genotypes to different classes of resistance, consistent with the results obtained for the remaining traits. These data suggest that using both necrotic leaf area (PLACN) bearing pycnidia and PYC dens can improve selection for quantitative STB resistance.
Use of low-quality water for supplemental irrigation is expected to become soon a common practice in the Mediterranean area, where durum wheat is the main cultivated cereal. Breeding for salt stress tolerance may contribute to the improvement of wheat resilience to irrigation with brackish water. Various traits can be considered as indicators of salt stress tolerance, which include agronomical and physiological criteria. However, the complexity of salinity tolerance mechanisms, the G × E interaction and the lack of correlation between controlled and open field conditions causes uncertainty in the selection process. The present review highlights the main advantages and limitations of different agronomical and physiological traits used in screening for salt stress tolerance in wheat. Special focus is given to carbon and nitrogen isotope discrimination, that remains a bottleneck in breeding for salt stress tolerance. The use of different statistical tools to analyse data related to salt stress tolerance is also discussed in this review.
The distribution of soil organic matter (SOM), nitrogen (N), potassium (K), total calcium carbonate (CaCO3) and pH was studied in relation to three soil tillage practices: conventional (CT) using mouldboad plough followed by three crossing of off-set disc harrow, tooth harrow and seed drill, Reduced (RT) using a chisel, and no-till (NT) using direct driller and 2 plant species: Vicia faba and Durum wheat, grown in a clayey soil of the semi-arid region of Kef (North western Tunisia) during three years 2009-2011. Results showed that, under NT, Vicia faba increased SOM and N in the first fifteen centimeters by 20% and 84% respectively as compared to the CT, and reduced soil pH by 0.1 unit. Indeed, Vicia faba benefited from the residues of the Durum wheat. In contrast, CT buried the residues of the previous crop increasing the rate of SOM and N in the subsoil (30-45 cm depth). This made clear that NT, had the benefit of improving top-soil fertility and putting soil nutrients at the reach of the Vicia faba plant roots. Moreover, NT increased the concentration of K in the top-soil which helped seedlings and young plants resisting biotic and non biotic stresses imposed by the semi-arid environment.
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