Characterization of Mediterranean Durum Wheat for Resistance to Pyrenophora tritici-repentis

Abstract

Tan spot (TS), caused by the fugus Pyrenophora tritici-repentis (Ptr), has gained significant importance in the last few years, thereby representing a threat to wheat production in all major wheat-growing regions, including Tunisia. In this context, we evaluated a Mediterranean collection of 549 durum wheat accessions under field conditions for resistance to Ptr over two cropping seasons in Jendouba (Tunisia), a hot spot for Ptr. The relative disease severities showed significant phenotypic variation from resistance to susceptibility. The correlation between disease scores over the two trials was significant, as 50% of the accessions maintained good levels of resistance (resistant–moderately resistant). Seedling- and adult-stage reactions were significantly correlated. The ANOVA analysis revealed that the genotype term is highly significant at the adult stage, thus emphasizing the high genetic variability of the tested accessions. Reaction-type comparison among and between countries revealed a high diversity of TS resistance. Plant height (PH) was negatively correlated to disease scores, indicating that PH might either have a significant effect on TS severity or that it can be potential disease escape traits. The evaluation of this collection allowed for the identification of potential diverse resistance sources to Ptr that can be incorporated in breeding programs.

Genome-wide association analysis of tan spot disease resistance in durum wheat accessions from Tunisia

“…The 235 durum wheat accessions were evaluated for resistance to tan spot at the adult plant stage under field conditions at the CRP Wheat Septoria Precision Phenotyping Platform, Kodia Experimental Station (36°32′51.89 N, 9°0′40.73 E), National Institute of Field Crops, Bou Salem, Tunisia. This Station is considered a very prevalent hot spot site for tan spot disease in most years ( Laribi et al, 2021 ; 2022b ). Field evaluations were carried out during the 2017–2018, 2018–2019 and 2021–2022 cropping seasons.…”

“…“Nasr,” the moderately susceptible “Karim,” and the resistant cv. “Salim” ( Laribi et al, 2021 ; 2022b ). Plots were irrigated to create favorable conditions for disease development and standard wheat agronomic practices were carried out to maintain the crops.…”

“…The field evaluations were carried out under natural inoculum conditions in 2017–2018, while in 2018–2019 and 2021–2022, wheat stubble infected with P. tritici-repentis and collected from previous cropping seasons was added as an inoculum source as described by Laribi et al (2022b) . Infected leaves and debris were collected and the presence of Ptr was confirmed ( Laribi et al, 2019 ; 2021 ; 2022b ). The occurence of races 2, 5, 6, 7, and 8 was reported in the experimental station ( Laribi et al, 2019 ; 2021 ).…”

“…The contrasting environmental conditions of North Africa and the Mediterranean basin have led to the development of a widely diversified collection of local accessions ( Mercer and Perales, 2010 ; Ouaja et al, 2021 ). Several studies reported that landraces from the secondary centers of wheat diversity such as the horn of Africa region and the Mediterranean region are genetically diverse and tolerant to both abiotic and biotic stresses ( Mengistu et al, 2016 ; Kabbaj et al, 2017 ; Ouaja et al, 2020 ; Laribi et al, 2021 ; Ouaja et al, 2021 ; Ben M’Barek et al, 2022 ; Ferjaoui et al, 2022 ; Laribi et al, 2022b ). Thus, Mediterranean landraces represent an important potential source for broadening the genetic background of elite durum wheat cultivars and for the introgression of potential novel genes for key traits into these cultivars.…”

“…Nevertheless, it is presumed that natural genetic variability in wheat was gradually lost in the process of domestication and also in the course of natural and human selection pressure for the improvement of modern cultivars ( Diamond, 2002 ; Haudry et al, 2007 ; Rahman et al, 2020 ). Mediterranean durum wheat landraces were found to be genetically diverse, highly adapted to environmental conditions and resistant or tolerant to several abiotic and biotic stresses ( Lopes et al, 2015 ; Ben M’Barek and Ghaffary, 2021 ; Laribi et al, 2021 ; 2022b ; Ben M’Barek et al, 2022 ). Few studies, however, have evaluated the phenotypic and genotypic diversity of Tunisian durum wheat accessions, provided by the National Gene Bank of Tunisia ( Medini et al, 2005 ; Robbana et al, 2019 ; 2021 ; Slim et al, 2019 ; Ouaja et al, 2021 ).…”