Phenotypic and Molecular Evaluation of some Advanced and Elite Bread Wheat Lines to Pyrenophora tritici-repentis, the Causal Agent of Tan Spot Disease

In this study, Advanced Regional Wheat Yield Trials (ARWYT) and Elite Regional Wheat Yield Trials (ERWYT) lines of Northern warm and humid zone were evaluated against Pyrenophora tritici-repentis isolate P8 (race 8), the causal agent of tan spot. Wheat lines were planted in three replications and seedlings were inoculated with the conidia of the isolate at two-leaf stage. Cultivars BR34 and Grandin were used as resistant and susceptible checks, respectively. Evaluation of ERWYT lines of year 2012 (N=20) and 2013 (N=20) showed that only one line ER-N-91-15 (year 2012) and four lines ER-N-92-5, ER-N-92-9, ER-N-92-12 and ER-N-92-20 (year 2013) were resistant to P8 isolate and the remaining lines were moderately susceptible, susceptible or highly susceptible. Furthermore, evaluation of ARWYT lines of year 2013 (AR-N-92) showed that out of 40 lines, only line AR-N-92-39 was resistant to P8 isolate. In addition, the reaction of these lines to ToxA infiltration were evaluated along with PCR screening for the presence or absence of the susceptibility gene, Tsn1. In total, 19 lines were recorded as susceptible to ToxA infiltration assay. PCR screening using gene specific primers showed that the necrosis observed after ToxA infiltration is absolutely correlated with the presence of Tsn1. Generally, the results of this study revealed that most of the wheat genotypes are susceptible to this disease, which is mostly due to lack of screening to the disease during breeding programs.