Phenotyping Mediterranean Durum Wheat Landraces for Resistance to Zymoseptoria tritici in Tunisia

Abstract

Durum wheat landraces have huge potential for the identification of genetic factors valuable for improving resistance to biotic stresses. Tunisia is known as a hot spot for Septoria tritici blotch disease (STB), caused by the fungus Zymoseptoria tritici (Z. tritici). In this context, a collection of 3166 Mediterranean durum wheat landraces were evaluated at the seedling and adult stages for STB resistance in the 2016–2017 cropping season under field conditions in Kodia (Tunisia). Unadapted/susceptible accessions were eliminated to reach the final set of 1059 accessions; this was termed the Med-collection, which comprised accessions from 13 countries and was also screened in the 2018–2019 cropping season. The Med-collection showed high frequency of resistance reactions, among which over 50% showed an immune reaction (HR) at both seedling and adult growth stages. Interestingly, 92% of HR and R accessions maintained their resistance levels across the two years, confirming the highly significant correlation found between seedling- and adult-stage reactions. Plant Height was found to have a negative significant effect on adult-stage resistance, suggesting that either this trait can influence disease severity, or that it can be due to environmental/epidemiological factors. Accessions from Italy showed the highest variability, while those from Portugal, Spain and Tunisia showed the highest levels of resistance at both growth stages, suggesting that the latter accessions may harbor novel QTLs effective for STB resistance.

Specific virulence patterns in Tunisian Zymoseptoria tritici strains isolated from bread and durum wheat

“…Although a strong correlation of disease severity between seedling and adult stages was previously observed (Ben M'Barek et al, 2022; Ferjaoui et al, 2022), there have been some exceptions in the case of the Z . tritici –BW pathosystem; some qualitative genes uniquely identified either at the seedling stage such as Stb7 and Stb10 or the adult stage, for instance, Stb8 and Stb17 (Brown et al, 2015).…”

“…The BW variety Tahent displayed a high level of resistance to all strains regardless of species origin, which suggests that it may harbour various novel resistance genes that can be further investigated through whole‐genome sequencing. However, this was not the case for Dhahbi and Monastir varieties, which are known to be moderately resistant at the adult stage under field conditions (Ben M'Barek et al, 2022) in the north‐western region.…”

“…The DW varieties Karim and Chtioui and the BW varieties Farina Arbi, Haidra and Salammbô were the most susceptible. Hence, Farina Arbi and Karim, which were previously shown to be susceptible in the field, could be used as susceptible local checks in the Tunisian national wheat resistance breeding programmes (Bel Hadj Chedli et al, 2020; Ben M'Barek et al, 2022). The remaining varieties need to be further tested in field conditions to confirm their susceptibility at adult stage in different environments.…”

“…Several studies conducted in Tunisia with regard to DW landraces have shown that these latter may harbour sources of resistance to Z . tritici (Ben M'Barek et al, 2022; Ferjaoui et al, 2022). Ferjaoui et al (2022) demonstrated that the observed STB resistance in the Tunisian landrace Agili39 is due to two minor and two major quantitative trait loci (QTLs) acting in an additive mode and provided evidence that the broad efficacy of this resistance was due to a natural pyramiding of these QTLs.…”

Genome-Wide Identification and Expression Profiling of Pathogenesis-Related Protein 1 (PR-1) Genes in Durum Wheat (Triticum durum Desf.)

“…Indeed, Tunisian durum is known by its allelic richness and ability to resist drought [ 42 ] and to tolerate biotic stresses, such as the Fusarium head infection [ 43 ] and Septoria tritici blotch disease (STB), the causal agent of the most agronomically and economically destructive fungi, Zymoseptoria tritici [ 44 ]. The latest agent can cause a loss of yield with an average of 5–35% [ 45 ].…”