برهمکنش‌های فنوتیپی و مولکولی قارچ Parastagonospora nodorum و گندم

Parastagonospora nodorum, the causal agent of Septoria nodorum blotch (SNB) disease, as one of the most important pathogens of wheat is widespread around the world. This fungus has emerged as a model for pathogenesis of necrotrophic fungal interaction due to production of various pathogenicity components such as extracellular enzymes, secondary metabolites and toxins. P. nodorum produces several host-specific toxins known as necrotrophic effectors (NEs) named SnToxN which interacts with a wheat susceptibility gene (named SnnN), regarded as inverse gene for gene model, leading to effector-triggered susceptibility (ETS), host cell death and disease development. This study was design to i) determine the virulence pattern of different isolates of P. nodorum on different Iranian and foreign wheat cultivars and ii) to detect the frequency of necrotrophic effector encoding genes SnToxA, SnTox1 and SnTox3 in these isolates and Tsn1 and Snn1 susceptibility genes in wheat germplasms. To do so, pathogenicity test of 32 different isolates of P. nodorum collected from Fars, Kohgiluyeh and Boyer-Ahmad, Khuzestan and Golestan provinces plus standard isolate SN15 was conducted on 40 wheat cultivars including 19 newly introduced Iranian cultivars and 21 foreign cultivars consisting differential lines BG261, Grandin, Chinese spring and BR34. Experiments were conducted in factorial randomized complete block design and the plant reaction to the fungus was evaluated based on leaf spot percentage at seven days post-inoculation (DPI). Disease severity data was analyzed using SAS software and least significant differences (LSD) test. To detect necrotrophic effector and susceptibility genes, specific primes were used in multiplex PCR reaction and then five amplicons were sequenced for validation. Wheat cultivars were categorized into five groups resistant, moderately resistant, moderately susceptible, susceptible and highly susceptible based on their reaction to fungal isolates. Necrotrophic effector genes SnTox1, SnTox3 and SnToxA were more frequent in fungal isolates respectively. Snn1 was also more abundant than Tsn1 in wheat cultivars. Also, there was a significant correlation between disease severity and frequency of necrotrophic effector genes. Fungal isolates with more necrotrophic effector genes were more virulent. The present study can extend our knowledge of molecular basis in P. nodorum-wheat interactions in Iran.