Genetic control of juvenile resistance to powdery mildew in spring bread wheat cultivars from the VIR collection

Abstract

Background. Bread wheat (Triticum aestivum L.) is one of the major food crops of humankind. Powdery mildew, caused by Blumeria graminis f. sp. tritici, is the most destructive foliar disease capable of causing great yield losses in epidemic years. Breeding for resistance to powdery mildew is the most economical and effective way to control this disease. By now, 68 loci were identified to contain more than 90 alleles of resistance to powdery mildew in wheat. However, there is a permanent necessity in finding new sources of resistance.The objective of the present study was to characterize the seedling powdery mildew resistance in some spring bread wheat varieties from the VIR collection and determine the inheritance of powdery mildew resistance in these accessions.Materials and methods. The powdery mildew resistant varieties ‘SW Kungsjet’ (k-66036), ‘SW Kronjet’ (k-66097), ‘Boett’ (k-66353), ‘Batalj’ (k-67116), ‘Stilett’ (k-67119) ‘Pasteur’ (k-66093) were crossed with a resistant line ‘Wembley 14.31’ (k-62557) containing the Pm12 gene, and with ‘SW Milljet’ (k-64434); the variety ‘Sibirka Yartsevskaya’ (k-38587) was used as a susceptible parent and control. The hybrid populations F2 were inoculated with the fungus population from local field and evaluated. The powdery mildew population manifested virulence to Pm1a, Pm2, Pm3a-f, Pm4a-b, Pm5a, Pm6, Pm7, Pm8, Pm9, Pm10, Pm11, Pm16, Pm19, Pm28, and avirulence to Pm12. The degree of resistance was assessed on days 8 and 10 after the inoculation using the Mains and Dietz scale (Mains, Dietz, 1930). The castrated flowers in the spikes were pollinated using the twell-method (Merezhko et al., 1973). Chi-squared for goodness of fit test was used to determine deviation of the observed data from the theoretically expected segregation.Results. According phytopathological and genetic tests, juvenile resistance in the varieties ‘SW Kungsjet’, ‘SW Kronjet’, ‘Boett’, ‘Batalj’, ‘Stilett’ and ‘Pasteur’ is controlled by dominant genes, which differ from Pm1a, Pm2, Pm3a-f, Pm4a-b, Pm5a, Pm6, Pm7, Pm8, Pm9, Pm10, Pm11, Pm12, Pm16, Pm19, and Pm28. The varieties ‘SW Milljet’, ‘SW Kronjet’ and ‘Pasteur’ had identical resistance genes. Genetic control of juvenile resistance to powdery mildew in ‘Batalj’, ‘Boett’, ‘Stilett’, ‘SW Milljet’, ‘SW Kungsjet’, ‘Pasteur’ was governed by different genes.Conclusions. The varieties ‘SW Kungsjet’, ‘SW Kronjet’, ‘Boett’ have been maintaining adult and seedling resistance since 2005, and ‘Batalj’, ‘Stilett’ and ‘Pasteur’ since 2017. Seedling resistance of these varieties to local powdery mildew population is controlled by dominant genes. A high degree of resistance was displayed by ‘SW Kungsjet’ and ‘SW Kronjet’ in the Novosibirsk Province, while ‘SW Kungsjet’ was resistant to mildew populations of Tatarstan. The variety ‘Pasteur’ manifested seedling resistance to leaf rust, and ‘SW Kungsjet’ was resistant to loose smut. By summing all the results, it may be suggested that the varieties ‘SW Kungsjet’, ‘SW Kronjet’, ‘Boett’, ‘Batalj’, ‘Stilett’ and ‘Pasteur can serve as good donors of powdery mildew resistance in wheat breeding.