Molecular approaches in identifying leaf rust resistance genes in Russian wheat varieties

Russian soft wheat varieties are screened with the use of molecular markers of Lr genes. A low genetic diversity is found among leaf rust resistant varieties, in which genes Lr9 and Lr19 dominate. There are no highly effective genes Lr25, Lr29, and Lr39(41) and adult plant resistance genes Lr37 and Lr21 in the studied varieties. Among genes with limited effectiveness, the most prevalent are genes Lr10 and Lr26, respectively in 45 and 10% of the varieties.     

Investigation of soilborne mosaic virus diseases transmitted by <Emphasis Type="Italic">Polymyxa graminis</Emphasis> in cereal production areas of the Anatolian part of Turkey

Polymyxa graminis is the vector of several important viruses, including Soilborne cereal mosaic virus, Wheat spindle streak mosaic virus, Barley yellow mosaic virus and Barley mild mosaic virus, of winter cereals worldwide. Surveys were carried out to detect these viruses and their vector P. graminis in 300 soil samples from the main wheat and barley production areas of the Anatolian part of Turkey collected in May 2002, June 2004 and May 2005. For these surveys, various susceptible wheat and barley cultivars were pot grown in the collected soil samples in a greenhouse and then analysed using ELISA and RT-PCR to detect the presence of different virus species. In addition, a combination of light microscopy following roots staining with acid fuchsin and PCR was used for detection of P. graminis. All soil samples analysed were found to be free of these soilborne viruses and their vector.     

A controlled environment test for resistance to Soil-borne cereal mosaic virus (SBCMV) and its use to determine the mode of inheritance of resistance in wheat cv. Cadenza and for screening Triticum monococcum genotypes for sources of SBCMV resistance

Several wheat genotypes, including eight with known field responses, were evaluated for their reaction to Soil-borne cereal mosaic virus (SBCMV, genus Furovirus) by growing in naturally infested soil under controlled environment conditions. Virus antigen titres in the foliage 8–9 weeks after sowing mostly reflected the field responses, showing that growth chamber-based tests can be used to improve the speed and reliability of germplasm screening. Such tests were used to determine the mode of inheritance of the SBCMV resistance in cv. Cadenza, commonly used in UK wheat-breeding programmes. One hundred and eleven doubled haploid (DH) lines derived from an F ₁ of a cross between cvs Cadenza (resistant) and Avalon (susceptible) were evaluated. This DH population segregated for the reaction to SBCMV in a ratio of 1 : 1 (resistant : susceptible). This suggests that the SBCMV resistance is controlled by a single gene locus. As a first step towards identification of new sources of improved SBCMV resistance (e.g. immunity) as well as sources of the resistance to the virus vector, Polymyxa graminis , a set of 26 Triticum monococcum lines of diverse geographical origin was also screened. Most lines were susceptible to SBCMV, but one line of Bulgarian origin was resistant to the virus and possibly partially resistant to the virus vector.     

RNAi as an emerging approach to control Fusarium head blight disease and mycotoxin contamination in cereals

Fusarium graminearum is a major fungal pathogen of cereals worldwide, causing seedling, stem base and floral diseases, including Fusarium head blight (FHB). In addition to yield and quality losses, FHB contaminates cereal grain with mycotoxins, including deoxynivalenol, which are harmful to human, animal and ecosystem health. Currently, FHB control is only partially effective due to several intractable problems. RNA interference (RNAi) is a natural mechanism that regulates gene expression. RNAi has been exploited in the development of new genomic tools that allow the targeted silencing of genes of interest in many eukaryotes. Host‐induced gene silencing (HIGS) is a transgenic technology used to silence fungal genes in planta during attempted infection and thereby reduces disease levels. HIGS relies on the host plant's ability to produce mobile small interfering RNA molecules, generated from long double‐stranded RNA, which are complementary to targeted fungal genes. These molecules are transferred from the plant to invading fungi via an uncharacterised mechanism, to cause gene silencing. Here, we describe recent advances in RNAi‐mediated control of plant pathogenic fungi, highlighting the key advantages and disadvantages. We then discuss the developments and implications of combining HIGS with other methods of disease control. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.