Genetic control of resistance to soilborne wheat mosaic virus in Brazilian cultivars of Triticum aestivum L. Thell.

In Southern Brazil, under ideal conditions Soilborne Wheat Mosaic Virus (SBWMV) induces yield reductions to the wheat crop of over 50%. The only effective way of controlling the disease is through resistance. However, the inheritance of resistance is not been fully understood. The purpose of this work was to study the genetic control of resistance to SBWMV. Crosses were carried out between the resistant wheat cultivar Embrapa 16 and the susceptible cultivars BR 23 and IAC 5-Maringa, at the National Wheat Research Centre, Passo Fundo, RS, Brazil. The parents, F-1, F-2, and backcrosses were sown in plots in a field where soil was naturally infested with the vector of the virus, the fungus Polymyxa graminis, in order to promote natural infection. All plants were individually evaluated for severity and type of lesions, according to a scale of 0 to 5, where, 0 = absence of symptoms and 5 = plants severely affected by mosaic plus dwarfing and rosetting. The statistical analyses of the data showed broad sense heritability values between 43% and 55%. The data suggested the presence of two genes controlling resistance to SBWMV in the segregating population of both crosses.