Viruses Without Borders: Global Analysis of the Population Structure, Haplotype Distribution, and Evolutionary Pattern of Iris Yellow Spot Orthotospovirus (Family Tospoviridae, Genus Orthotospovirus)

Iris yellow spot, caused by Iris yellow spot orthotospovirus (IYSV) (Genus: Orthotospovirus, Family: Tospoviridae), is an important disease of Allium spp. The complete N gene sequences of 142 IYSV isolates of curated sequence data from GenBank were used to determine the genetic diversity and evolutionary pattern. In silico restriction fragment length polymorphism (RFLP) analysis, codon-based maximum likelihood studies, genetic differentiation and gene flow within the populations of IYSV genotypes were investigated. Bayesian phylogenetic analysis was carried out to estimate the evolutionary rate. In silico RFLP analysis of N gene sequences categorized IYSV isolates into two major genotypes viz., IYSV Netherlands (IYSVNL; 55.63%), IYSV Brazil (IYSVBR; 38.73%) and the rest fell in neither group [IYSV other (IYSVother; 5.63%)]. Phylogenetic tree largely corroborated the results of RFLP analysis and the IYSV genotypes clustered into IYSVNL and IYSVBR genotypes. Genetic diversity test revealed IYSVother to be more diverse than IYSVNL and IYSVBR. IYSVNL and IYSVBR genotypes are under purifying selection and population expansion, whereas IYSVother showed decreasing population size and hence appear to be under balancing selection. IYSVBR is least differentiated from IYSVother compared to IYSVNL genotype based on nucleotide diversity. Three putative recombinant events were found in the N gene of IYSV isolates based on RDP analysis, however, RAT substantiated two among them. The marginal likelihood mean substitution rate was 5.08 × 10–5 subs/site/year and 95% highest posterior density (HPD) substitution rate between 5.11 × 10–5 and 5.06 × 10–5. Findings suggest that IYSV continues to evolve using population expansion strategies. The substitution rates identified are similar to other plant RNA viruses.

THE EFFECTIVENESS OF BIOLOGICAL FUNGICIDES AGAINST THE SPARE PARTS OF THE LEAVES OF WINTER WHEAT IN THE CONDITIONS OF THE CENTRAL ZONE OF THE KRASNODAR TERRITORY

The biologization of plant growing in modern conditions is becoming an urgent trend in agriculture, which helps to reduce the pesticide load. An important aspect of the transition to organic farming is the use of fungicides based on living microorganisms and their metabolic products to curb the development of diseases. Studies were carried out to assess the effectiveness of modern biofungicides against leaf septoria (Septoria tritici) and yellow spot (Pyrenophora tritici-repentis) of winter wheat - Vitaplan, SP, Gamair, SP, Pseudobacterin-2, Zh, Rizoplan, Zh, Trichocin, SP, Fitosporin -M, SP. Fungicide Amistar Extra, SK was used as a chemical standard. The work was carried out in the conditions of the central zone of the Krasnodar Territory in 2019–2020 on the variety Grom, susceptible to leaf spots. The meteorological conditions of the first year of research were favorable for the development of pathogens of leaf spots. In the second year, conditions were extreme, both for the growth of wheat plants and for the development of phytopathogens. For two years of research, the most effective biofungicides against leaf septoria were Fitosporin-M, SP, Pseudobacterin-2, Zh and Vitaplan, SP, the biological effectiveness was 50.0%, 50.0% and 47.1%, respectively; against yellow spot - Vitaplan, SP and Trichocin, SP, biological efficiency was 48.4% and 45.9%. The use of biological fungicides made it possible to save from 2.5% (Gamair, SP) to 12.6% (Trichocin, SP) of the winter wheat grain yield in comparison with the control (without treatment). The high economic efficiency of the use of biofungicides was established, the maximum net profit was noted in the variant treated with Fitosporin - M, SP (9540 rubles / ha)

Viral complexes in the Allium cepa L.- Frankliniella occidentalis P. interaction by DAS-ELISA in Baja California, Mexico

The onion (Allium cepa L.) is one of the main horticultural crops produced in Baja California, Mexico. In this crop, it has been observed presumptive viral symptoms, which are able to cause losses in yield and quality. Therefore, the objective of this study was to detect the associated virus in onion in high producing culture zones in Baja California. Plant material samples (symptomatic and asymptomatic) and trips insects were collected from commercial farming or areas. Commercial anti-serum were used for the detection of Iris yellow spot virus (IYSV), Tomato spot wilt virus (TSWV), Leek yellow spot virus (LYSV), Onion yellow dwarf virus (OYDV) and Garlic common latent virus (GarCLV). Seven indicator plants species were mechanically inoculated with onion sap (symptomatic and asymptomatic). The results showed the presence of IYSV, TSWV, OYDV and GarCLV in symptomatic onion plants. The plant samples showed a 77 % of incidence in the form of viral complexes and in a 23 % only the presence of LYSV was detected. The trips identified as Frankiniella occidentalis P. harbored IYSV, TSWV, LYSV, OYDV and GarCLV in the form of complexes in La Trinidad and San Quintin. The indicator plants did not show sympotoms of virosis. It is evident that F. occidentalis P. is responsible for the transmision of the analyzed viruses in this study in cultured onions. There are not previous reports for the detection of Orthotospovirus, Potyvirus and Carlavirus in Baja California onions.

Iris yellow spot virus (Iris yellow spot).

In 1981, de Avila et al. (1981) described a disease characterized by chlorotic and necrotic, eye-like or diamond-shaped lesions on onion scapes (referred to as 'sapeca') in southern Brazil. In 1989, Hall et al. (1993) observed a very similar disease in onion in the USA and detected a tospovirus, which was later shown by Moyer et al. (1993) to be Iris yellow spot virus on the basis of molecular and serological data. In 1998, a new tospovirus was isolated and characterized in the Netherlands from infected iris and leek and named Iris yellow spot virus (IYSV) (Cortês et al., 1998). This virus was subsequently found naturally infecting onion in several major onion-producing states of the USA and around the world (for reviews, see Gent et al., 2006 and Pappu et al., 2009). Gera et al. (1998b) reported that IYSV was responsible for a 'straw bleaching' disease on onion in Israel. In 1999, a 'sapeca' isolate from Brazil was identified as IYSV on the basis of biological, serological and molecular data (Pozzer et al., 1999). In Israel, Kritzman et al. (2000) reported natural IYSV infection of lisianthus grown in the field. IYSV has now been endemic in south-western Idaho and eastern Oregon in onion, leek and chive seed production fields for over 10 years. Losses caused by IYSV can reach 100% in onion crops, for example, in Brazil (Pappu et al., 2009). However, studies in the Netherlands in 2008 showed that latent infections of IYSV were common in onion crops but did not cause economic damage (NPPO of the Netherlands, 2008). Iris yellow spot represents an immediate and serious threat to sustainable and productive onion cropping systems around the world, and the recent detection of this disease in numerous onion-producing countries demonstrates that the disease is spreading rapidly in a range of environments. IYSV is on the EPPO Alert list (http://www.eppo.org/QUARANTINE/Alert_List/alert_list.htm).