Parastagonospora nodorum and Related Species in Western Canada: Genetic Variability and Effector Genes

• Published in: Phytopathology Vol. 110; no. 12; pp. 1946 - 1958
• Main Authors: Hafez, Mohamed, Gourlie, Ryan, Despins, Therese, Turkington, Thomas K, Friesen, Timothy L, Aboukhaddour, Reem
• Format: Journal Article
• Language: English
• Published: United States 01.12.2020
• Subjects: Ascomycota - genetics; Canada; Plant Diseases; Canada; host selective toxins; haplotypes; necrotrophic effectors; ToxA; population biology; Tsn1; SNB; SnTox1; disease control and pest management; SnTox3
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-05-20-0207-R

is an important fungal pathogen that causes Septoria nodorum blotch (SNB) in wheat. This pathogen produces several necrotrophic effectors that act as virulence factors; three have been cloned, SnToxA, SnTox1, and SnTox3. In this study, and its sister species f. ( ) were isolated from wheat node and grain samples collected from distanced sites in western Canada during 2018. The presence of effector genes and associated haplotypes were determined by PCR and sequence analysis. An internal transcribed spacer-restriction fragment length polymorphism test was developed to distinguish between leaf spotting pathogens ( , , , and ). was mainly recovered from wheat nodes and to a lesser extent from the grains, while was exclusively isolated from grain samples. The effector genes were present in almost all isolates, with the haplotype 5 (H5) being most prevalent, while a novel haplotype (denoted here H21) is reported for the first time. In , only combinations of and genes were present. A haplotype network was also constructed to assess the evolutionary relationship among globally found haplotypes to date. Finally, cultivars representing wheat development in Canada for the last century were tested for sensitivity to Sn-effectors and to the presence of , the sensitivity gene. Of tested cultivars, 32.9 and 56.9% were sensitive to SnTox1 and SnTox3, respectively, and was present in 59% of the cultivars. In conclusion, and were prevalent wheat pathogens in Canada with a potential tissue-specific colonization capacity, while producing necrotrophic effectors to which wheat is sensitive.