Virulence Structure of the Wheat Powdery Mildew Population in Serbia

Powdery mildew is a common, economically important disease in the wheat growing area of Serbia. A large-scale virulence survey of its causal agent Blumeria graminis f. sp. tritici population was performed in the period 1995–2013. A total of 1013 isolates were recovered from the collected chasmothecial samples. Among them, 862 unique pathotypes were identified using a differential set of 20 wheat lines with known powdery mildew (Pm) resistant genes. The pathogen was highly diverse. Number of virulence genes (virulence complexity) per isolate was large, supporting a constant need to extend the differential set of wheat with newly identified Pm genes. Virulence frequencies to Pm6, Pm7, and Pm5+8 were high throughout the 19-year period, in contrast with that to Pm5+6, which was consistently at a low level. The most significant change in the population was observed for virulence to the Pm2+4b+6 gene combination, with an increasing frequency of virulence to this gene combination over the years. High virulence complexity and genetic diversity of the population are the most influential factors for the damaging epidemics that this pathogen can cause.

New Pathotype Nomenclature for Better Characterisation the Virulence and Diversity of Blumeria graminis f.sp. avenae Populations

Fungal cereal pathogens, including Blumeria graminis f.sp. avenae, have the ability to adapt to specific conditions, which in turn leads to overcoming host resistance. An important aspect is the standardized way of characterizing the races and pathotypes of the pathogen. In the presented work, for the first time it was proposed to use a unified letter code that allows describing the pathotypes of B. graminis f.sp. avenae. The set of 14 oat genotypes were used as a differential set. This set included genotypes having so far described powdery mildew resistance genes Pm1–Pm11, and two genotypes (A. sterilis and A. strigosa) with effective sources of resistance to Bga. Based on the analysis of 160 Bga isolates collected in 2016–2019 from 4 locations in Poland, the most numerous was the TBBB pathotype, represented by 30% of the tested isolates. It was present in all analyzed populations. Subsequently, 8.1% and 6.3% of the isolates represented the TBCB and RBBB pathotypes, respectively.

Current and Future Pathotyping Platforms for Plasmodiophora brassicae in Canada

Clubroot, caused by Plasmodiophora brassicae, is one of the most detrimental threats to crucifers worldwide and has emerged as an important disease of canola (Brassica napus) in Canada. At present, pathotypes are distinguished phenotypically by their virulence patterns on host differential sets, including the systems of Williams, Somé et al., the European Clubroot Differential set, and most recently the Canadian Clubroot Differential set and the Sinitic Clubroot Differential set. Although these are frequently used because of their simplicity of application, they are time-consuming, labor-intensive, and can lack sensitivity. Early, preventative pathotype detection is imperative to maximize productivity and promote sustainable crop production. The decreased turnaround time and increased sensitivity and specificity of genotypic pathotyping will be valuable for the development of integrated clubroot management plans, and interest in molecular techniques to complement phenotypic methods is increasing. This review provides a synopsis of current and future molecular pathotyping platforms for P. brassicae and aims to provide information on techniques that may be most suitable for the development of rapid, reliable, and cost-effective pathotyping assays.

Pathogenic specialisation in Uromyces viciae-fabae in Australia and rust resistance in faba bean

The pathogen Uromyces viciae-fabae causes rust (a fungal disease) on faba bean (Vicia faba). This disease limits faba bean production in Africa, Asia, Europe and Australia. The development of resistant cultivars to U. viciae-fabae is the optimal solution for sustainable disease management. However, unknown virulence in Australian U. viciae-fabae populations has confounded resistance breeding. This study examined differences in virulence amongst Australian U. viciae-fabae isolates collected from various locations and established a differential set of faba bean genotypes. Ten rust isolates were collected from the major faba bean growing regions in Australia and single spore cultures produced. These cultures were subsequently used for assessing virulence on 40 diverse faba bean genotypes. Based on the host-pathogen interactions, 12 putative host genotypes were identified as a differential set. A nomenclature system was subsequently developed using the binary pathotype naming system. Based upon host-pathogen interactions, nine virulence patterns were detected, and the isolates were named using the new nomenclature. We report characterisation and naming of U. viciae-fabae pathotypes using differential genotypes in Australia. This differential set will help identify and track the evolution of new virulence in pathogen population and will assist pyramiding of rust resistance genes.

Dynamics of Race Structures of the Rice Blast Pathogen Population in Heilongjiang Province, China From 2006 Through 2015

Rice blast caused by the fungus Magnaporthe oryzae is one of the most destructive diseases of rice. Its control through the deployment of host resistance genes would be facilitated by understanding the pathogen’s race structure. Here, dynamics of race structures in this decade in Heilongjiang province were characterized by Chinese differential cultivars. Two patterns of dynamics of the race structures emerged: both race diversity and population-specific races increased gradually between 2006 and 2011, but they increased much more sharply between 2011 and 2015, with concomitant falls in both the population-common races and dominant races. Four races (ZD1, ZD3, ZD5, and ZE1) were among the top three dominant races over the whole period, indicating that the core of the race structure remained stable through this decade. On the host side, the composition of resistance in the cultivar differential set could be divided in two: the three indica-type entries of the differential set expressed a higher level of resistance to the population of M. oryzae isolates tested than did the four japonica-type entries. The cultivars Tetep and Zhenlong 13 as well as two additional resistance genes α and ε were confirmed as the most promising donors of blast resistance for the local rice improvement programs. [Formula: see text]Copyright © 2019 The Author(s). This is an open-access article distributed under the CC BY-NC-ND 4.0 International license .

Principal approaches and achievements in studying race composition of wheat stem rust

Wheat stem rust caused by the biotrophic fungus Puccinia graminis f. sp. tritici is a dangerous disease that seriously damages the economics in many countries of the world. The review contains information about epidemics of wheat stem rust and causes of their emergence worldwide. Recently wheat stem rust epidemics have been recorded in the northern regions of Kazakhstan and on the territories adjacent to Omsk Region of Russia. It has been shown that severe wheat stem rust epidemics occur mainly due to the emergence of new virulent races of the disease agent and to growing susceptible wheat cultivars. New methods of studying the race composition of the fungus are described as well as the use of the previous and current differential sets for race determination of P. graminis f. sp. tritici. The results of developing molecular markers and assessing their effectiveness in studying stem rust races are presented. Wheat stem rust races dominant in major grain-growing countries of the globe and their typical peculiarities are described. The paper contains information on identifcation of race Ug99 and of its variations including data on areas of their dissemination and on their virulence to Sr-resistance genes. The existence and emergence of other races of the agent potentially dangerous for commercially important genes for stem rust resistance is also described. Currently in nature strongly virulent races of P. graminis f. sp. tritici are circulating with wide geographical coverage and their virulence is absolutely different from the virulence of race Ug99. Historical and modern data on studying the race composition of the pathogen in Kazakhstan are summarized. It is stated that the use of the old standard differential set and an incomplete North American system of race nomenclature in experiments prevents measuring similarity between Kazakhstani races and the worldwide known races of the pathogen. It has been shown that there is a need to continue studies on the intraspecies structure of the disease agent’s population in Kazakhstan with the use of the modern differential set, on determination of race composition and ways of emergence of new races potentially dangerous for commercial wheat varieties.