Comparative analysis of methods of assessing spring soft wheat for resistance to Parastagonospora nodorum and search for sources of a trait for breeding
In the conditions of Kirov region (2017-2021), 67 varieties of spring soft wheat were studied according to the degree of resistance to Septoria leaf blotch in the field against the background of the natural development of infection. Under laboratory conditions, the reaction of these wheat varieties to the pathogen was evaluated at the beginning of plant ontogenesis (juvenile resistance) in two experiments: assessment in the development phase of 2-3 leaves (roll culture) and evaluation of a trait on cut-off leaves. For inoculation of plants, local strains of P. nodorum were used. They were isolated from the affected leaves of spring soft wheat in the phase of milk-wax ripeness. All isolates have been identified by PCR as belonging to the species of P. nodorum. The validity of using laboratory methods of plant inoculation by P. nodorum for mass assessment of the gene pool and purposeful search for wheat genotypes resistant to Septoria is based on a reliable (at P≥0.95) correlation (r = 0.57) of resistance at the beginning of ontogenesis and in adult plants. Varieties belonging to one and the same groups in terms of resistance and susceptibility have an even closer relationship (r = 0.69; r = 0.71). It has been established that with an increase in the degree of affection at the beginning of ontogenesis, the biomass of the plant significantly (r = -0.68) decreases, on average by 28 % in the assortment. Of particular interest for breeding of spring wheat are varieties with the most favorable combination of low infection rate and resistance to Septoria leaf blotch during ontogenesis. These varieties include: Turinskaya, Egisar 29 (Russia), Mian Yong No.1, Yan Shi 4, Jin Mai 71 (China), SSL 25-26, SSL 84-85, UL Alta Blanca (USA).