Functional Transcomplementation between Wheat Dwarf Virus Strains in Wheat and Barley

A new geminialphasatellite associated with wheat dwarf virus identified in winter barley in France

Using a high-throughput sequencing (HTS) approach, we report the discovery of a new alphasatellite identified in a winter barley plant collected in France in 2022 that was also infected by wheat dwarf virus (WDV). The presence of the satellite and of WDV was confirmed by several independent PCR assays, and the complete genome sequence was determined. The circular satellite genome is 1424 nt long and shows typical hallmarks of members of the subfamily Geminialphasatellitinae, including a replication-associated hairpin with a CAGTATTAC sequence and a Rep-encoding open reading frame (ORF). It also possesses a second ORF, embedded in a different frame within the Rep ORF, which is also observed in clecrusatellites and a few other members of the family Alphasatellitidae. Pairwise sequence comparisons and phylogenetic analysis showed that this satellite represents a novel species. Its closest relatives are in the genus Colecusatellite, but it likely represents a new genus given its divergence from other genera of the subfamily Geminialphasatellitinae. Given that WDV was the only virus observed in coinfection with the satellite, the name "wheat dwarf virus-associated alphasatellite" is proposed for this novel agent.

Leveraging insect viruses and genetic manipulation for sustainable agricultural pest control

The potential of insect viruses in the biological control of agricultural pests is well-recognized, yet their practical application faces obstacles such as host specificity, variable virulence, and resource scarcity. High-throughput sequencing (HTS) technologies have significantly advanced our capabilities in discovering and identifying new insect viruses, thereby enriching the arsenal for pest management. Concurrently, progress in reverse genetics has facilitated the development of versatile viral expression vectors. These vectors have enhanced the specificity and effectiveness of insect viruses in targeting specific pests, offering a more precise approach to pest control. This review provides a comprehensive examination of the methodologies employed in the identification of insect viruses using HTS. Additionally, it explores the domain of genetically modified insect viruses and their associated challenges in pest management. The adoption of these cutting-edge approaches holds great promise for developing environmentally sustainable and effective pest control solutions. © 2023 Society of Chemical Industry.

Molecular evolution and phylogeographic analysis of wheat dwarf virus

Wheat dwarf virus (WDV) has caused considerable economic loss in the global production of grain crops. Knowledge of the evolutionary biology and population history of the pathogen remain poorly understood. We performed molecular evolution and worldwide phylodynamic analyses of the virus based on the genes in the protein-coding region of the entire viral genome. Our results showed that host-driven and geography-driven adaptation are major factors that affects the evolution of WDV. Bayesian phylogenetic analysis estimates that the average WDV substitution rate was 4.240 × 10-4 substitutions/site/year (95% credibility interval, 2.828 × 10-4-5.723 × 10-4), and the evolutionary rates of genes encoding proteins with virion-sense transcripts and genes encoding proteins with complementary-sense transcripts were different. The positively selected sites were detected in only two genes encoding proteins with complementary-sense, and WDV-barley are subject to stronger purifying selection than WDV-wheat. The time since the most recent common WDV ancestor was 1746 (95% credibility interval, 1517-1893) CE. Further analyses identified that the WDV-barley population and WDV-wheat population experienced dramatic expansion-decline episodes, and the expansion time of the WDV-barley population was earlier than that of the WDV-wheat population. Our phylogeographic analysis showed that the WDV population originating in Iran was subsequently introduced to Europe, and then spread from Eastern Europe to China.

Asymmetric interactions between barley yellow dwarf virus -PAV and wheat dwarf virus in wheat

The deciphering of the epidemiology of a plant virus has long been focused on the study of interactions between partners of one pathosystem. However, plants are exposed to numerous viruses which lead to frequent co-infection scenarios. This can change characteristics of virus-vector-host interactions and could impact the epidemiology of viral diseases. Barley yellow dwarf virus-PAV (BYDV-PAV; species: Luteovirus pavhordei; genus Luteovirus), wheat dwarf virus (WDV; genus Mastrevirus) and their respective vectors (BYDV-PAV: e.g. Rhopalosiphum padi and WDV: Psammotettix alienus) are commonly found in cereal fields. Wheat plants co-infected with BYDV-PAV and WDV have been reported from field surveys, although epidemiological outcomes of BYDV-PAV - WDV interactions in planta have not yet been studied. Experiments were carried out to evaluate and compare, through different competition scenarios (i.e. single- and co- (simultaneous and sequential) inoculations), the efficiency of BYDV-PAV and WDV to infect, to accumulate in and to be spread between wheat plants. Moreover, the impact of competition scenarios on the biological parameters of these two viruses was evaluated at different stages of the infection and with plants at different ages at inoculation. Results showed i) that these viruses achieve their infection cycle and their plant-to-plant transmission with different efficiencies and ii) BYDV-PAV - WDV interactions lead to different phenotypes ranging from antagonism to synergism. Finally, when these two viruses share a host, the nature and strength of virus-virus interactions varied depending on the order of virus arrival, stages of the infection cycle and plant age at inoculation. Precisely, the introduction (i.e. co- and sequential inoculation) and infection process (i.e. virus accumulation) of BYDV-PAV in a wheat benefit from the presence of WDV. For the latter, the sympatry with BYDV-PAV exerts opposite pressure on parameters involved in virus introduction (i.e. benefit during sequential inoculation) and spread (i.e. lower transmission efficiency and virus accumulation in co-infected plants). In the context of increased potential exposure of crops to insect vectors, this study participates in a better understanding of the impact of BYDV-PAV and WDV co-infections on biological and ecological parameters of the diseases induced by these viruses.

Efficiency and Persistence of Movento® Treatment against Myzus persicae and the Transmission of Aphid-Borne Viruses

Neonicotinoids are widely used to protect fields against aphid-borne viral diseases. The recent ban of these chemical compounds in the European Union has strongly impacted rapeseed and sugar beet growing practices. The poor sustainability of other insecticide families and the low efficiency of prophylactic methods to control aphid populations and pathogen introduction strengthen the need to characterize the efficiency of new plant protection products targeting aphids. In this study, the impact of Movento^® (Bayer S.A.S., Leverkusen, Germany), a tetrameric acid derivative of spirotetramat, on Myzus persicae and on viral transmission was analyzed under different growing temperatures. The results show (i) the high efficiency of Movento^® to protect rapeseed and sugar beet plants against the establishment of aphid colonies, (ii) the impact of temperature on the persistence of the Movento^® aphicid properties and (iii) a decrease of approximately 10% of the viral transmission on treated plants. These observations suggest a beneficial effect of Movento^® on the sanitary quality of treated crops by directly reducing primary infections and indirectly altering, through aphid mortality, secondary infections on which the spread of disease within field depends. These data constitute important elements for the future development of management strategies to protect crops against aphid-transmitted viruses.