Resistance genes to Blumeria graminis and their products in cereals

Abstract

Powdery mildew is one of the most destructive wheat diseases, and it causes a constant need for the improvement of wheat resistance. Transfer of resistance genes from wild relatives into the wheat genetic pool could be an alternative to the use of fungicides. This review contains classification of powdery mildew resistance on different ontogenetic stages (seedling resistance and adult resistance), expression of the trait (quantitative and qualitative), and genes conferring resistance (wide-spectrum and race-specific resistance). Powdery mildew resistance genes are characterised; the number of identified resistance genes is constantly increasing, and in 2019 the number of genes / alleles was 89. The genes controlling the desired trait have originated from different wheat relatives, namely: rye (Secale cereale L.), Dasypyrum villosum (L.) P. Candargy (Haynaldia villosa Schur), Thinopyrum intermedium, and species from the genera Aegilops and Triticum. Resistance genes are classified by their products, chromosome localization, and presence of different alleles. For a number of genes, chromosome localization and the nature of protein products have not yet been determined. Attention is also focused on possible complications that could arise during the identification of new genes, when already known resistance genes / alleles could be falsely identified as new ones. Resistance genes protein products are mostly receptors, which are classified according to their domain structure. The most variable domains in these proteins are leucine-rich repeats (LRRs), which provide the specificity of the receptors. Interaction between pathogen effectors and plant resistance proteins occurs through direct physical interaction or through the intermediate signalling events. Resistance genes and their products have been described, based on the results of the experiments conducted on wheat and other model plants, including monocots (rice), although the information obtained on Arabidopsis thaliana has also been analyzed.