Abstract
Septoria tritici blotch (STB) of wheat, caused by the ascomycete Zymoseptoria tritici (formerly Mycosphaerella graminicola), is one of the most important foliar diseases of wheat. In Morocco, STB is a devastating disease in temperate wheat-growing regions, and the yield losses can exceed up to 50% under favorable conditions. The aims of this study were to identify sources of resistance to STB in Septoria Association Mapping Panel (SAMP), which is composed of 377 advanced breeding lines (ABLs) from spring bread wheat breeding program of ICARDA, and to identify loci associated with resistance to STB at seedling (SRT) as well as at the adult plant (APS) stages using genome-wide association mapping (GWAM). Seedling resistance was evaluated under controlled conditions with two virulent isolates of STB (SAT-2 and 71-R3) from Morocco, whereas adult plant resistance was assessed at two hot spot locations in Morocco (Sidi Allal Tazi, Marchouch) under artificial inoculation with a mixture of STB isolates. At seedling stage, 45 and 32 ABLs were found to be resistant to 71-R3 and SAT-2 isolates of STB, respectively. At adult plant stage, 50 ABLs were found to be resistant at hot spot locations in Morocco. Furthermore, 10 genotypes showed resistance in both locations during two cropping seasons. GWAM was conducted with 9,988 SNP markers using phenotypic data for seedling and the adult plant stage. MLM model was employed in TASSEL 5 (v 5.2.53) using principal component analysis and Kinship Matrix as covariates. The GWAM analysis indicated 14 quantitative trait loci (QTL) at the seedling stage (8 for isolate SAT-2 and 6 for isolate 71-R3), while 23 QTL were detected at the adult plant stage resistance (4 at MCH-17, 16 at SAT-17, and 3 at SAT-18). SRT QTL explained together 33.3% of the phenotypic variance for seedling resistance to STB isolate SAT-2 and 28.3% for 71-R3, respectively. QTL for adult plant stage resistance explained together 13.1, 68.6, and 11.9% of the phenotypic variance for MCH-17, SAT-17, and SAT-18, respectively. Identification of STB-resistant spring bread wheat germplasm in combination with QTL detected both at SRT and APS stage will serve as an important resource in STB resistance breeding efforts.
Highlights
Wheat is one of the most important crops produced in Morocco
Seventeen advanced breeding lines (ABLs) were resistant to Sidi Allal Tazi (SAT)-2 but susceptible to 71R3 isolate, while nine ABLs were highly resistant to 71-R3 but susceptible to SAT-2 isolate, and 13 ABLs exhibited resistance at seedling stage to both Septoria tritici blotch (STB) isolates tested
Of the 377 ABLs tested, 177 (46.9%) and 41 (10.8%) ABLs were found to be resistant at SAT-17 and SAT-18, respectively, 108 (28.6%) ABLs were resistant at MCH-17
Summary
Wheat is one of the most important crops produced in Morocco. A decline of about 37% in wheat production, from 4.1 MT in 2019 to 2.6 MT in 2020, was observed. This decline is almost 56% compared with the 5-year average due to a combination of a(biotic) stresses (FAO, 2020). Wheat is exposed to various fungal diseases that can cause significant yield losses. In Morocco, STB is a serious problem in temperate rainfall wheat-growing regions, which may cause up to 40% yield losses (Ezzahiri, 2001). Host plant resistance and the use of fungicides are used to limit STB-inflicted yield losses. Breeding for disease resistance remains the most economical, effective, and environment-friendly strategy to combat STB (Steiner et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
