Wheat Genotypes With Combined Resistance to Wheat Curl Mite, Wheat Streak Mosaic Virus, Wheat Mosaic Virus, and Triticum Mosaic Virus

Population genomic analysis of Aegilops tauschii identifies targets for bread wheat improvement

Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding.

INCIDENCE AND SPREAD OF CEREALS VIRUSES IN 2020–2021 IN UKRAINE

Cereals play a significant role in the Ukrainian economy and agriculture. Viral diseases can cause a serious reduction in yields. Aim. The aim of the work was to identify and determine the spread of grain viruses in the main cereal-growing regions of Ukraine in the period 2020–2021 using different methods of virus detection. Methods. Enzyme-linked immunosorbent assay was used to identify viruses using commercial test systems by for wheat streak mosaic virus (WSMV), barley stripe mosaic virus (BSMV), brome mosaic virus (BMV), wheat dwarf virus (WDV), High Plainswheat mosaic virus (HPWMoV), barley yellow dwarf virus-PAV (BYDV-PAV), barley yellow dwarf virus-MAV (BYDV-MAV), andcereal yellow dwarf virus-RPV (CYDV-RPV). Transmission electron microscopy was used for direct virus detection. Reverse transcription polymerase chain reaction was performed to identify viruses by molecular methods. Results. Summarizing the results obtained by different methods, we can say about the circulation of WSMV, HPWMoV, BSMV, BYDV-PAV, and BYDV-MAV in the Ukrainian agrocoenoses in 2020–2021. Significant prevalence and the dominant role of WSMV have been shown, with the degree of damage to symptomatic plants reaching 52 %. The spread of HPWMoV in Kyiv and Poltava regions has been established, although previously the virus was detected only in the eastern part of our country. WSMV was more likely to induce monoinfection (70 %). Conclusions. During the testing of symptomatic plants in the agrocenoses of Ukraine in 2020–2021 the most common were WSMV and HPWMoV (52 % and 19 %, respectively), also found BYDV-PAV in winter wheat and BYDV-MAV in oats.

Modeling Aceria tosichella biotype distribution over geographic space and time

The wheat curl mite, Aceria tosichella Keifer, one of the most destructive arthropod pests of bread wheat worldwide, inflicts significant annual reductions in grain yields. Moreover, A. tosichella is the only vector for several economically important wheat viruses in the Americas, Australia and Europe. To date, mite-resistant wheat genotypes have proven to be one of the most effective methods of controlling the A. tosichella-virus complex. Thus, it is important to elucidate A. tosichella population genetic structure, in order to better predict improved mite and virus management. Two genetically distinct A. tosichella lineages occur as pests of wheat in Australia, Europe, North America, South America and the Middle East. These lineages are known as type 1 and type 2 in Australia and North America and in Europe and South America as MT-8 and MT-1, respectively. Type 1 and type 2 mites in Australia and North America are delineated by internal transcribed spacer 1 region (ITS1) and cytochrome oxidase I region (COI) sequence differences. In North America, two A. tosichella genotypes known as biotypes are recognized by their response to the Cmc3 mite resistance gene in wheat. Aceria tosichella biotype 1 is susceptible to Cmc3 and biotype 2 is virulent to Cmc3. In this study, ITS1 and COI sequence differences in 25 different populations of A. tosichella of known biotype 1 or biotype 2 composition were characterized for ITS1 and COI sequence differences and used to model spatio-temporal dynamics based on biotype prevalence. Results showed that the proportion of biotype 1 and 2 varies both spatially and temporally. Greater ranges of cropland and grassland within 5000m of the sample site, as well as higher mean monthly precipitation during the month prior to sampling appear to reduce the probability of occurrence of biotype 1 and increase the probability of occurrence of biotype 2. The results suggest that spatio-temporal modeling can effectively improve A. tosichella management. Continual integration of additional current and future precipitation and ground cover data into the existing model will further improve the accuracy of predicting the occurrence of A. tosichella in annual wheat crops, allowing producers to make informed decisions about the selection of varieties with different A. tosichella resistance genes.

An Intimate Relationship Between Eriophyoid Mites and Their Host Plants - A Review

Eriophyoid mites (Acari Eriophyoidea) are phytophagous arthropods forming intimate relationships with their host plants. These mites are associated with annual and perennial plants including ferns, and are highly specialized with a dominant monophagy. They can be classified in different ecological classes, i.e., vagrant, gall-making and refuge-seeking species. Many of them are major pests and some of them are vectors of plant pathogens. This paper critically reviews the knowledge on eriophyoids of agricultural importance with emphasis on sources for host plant resistance to these mites. The role of species belonging to the family Eriophyidae as vectors of plant viruses is discussed. Eriophyoid-host plant interactions, the susceptibility within selected crops and main host plant tolerance/resistance mechanisms are discussed. Fundamental concepts, subjects, and problems emerged in this review are pointed out and studies are suggested to clarify some controversial points.