Abstract
Field survey study was conducted season (2017). Soybeans and weeds were weekly sampled randomly. Thrips adults were identified and counted. Detection of the virus isolate and the natural incidence was determined using; Mechanical transmission, host range, DAS-ELISA, RT-PCR. The natural incidence thrips individuals was detected depending on the SVNV% in thrips individuals and weeds hosts. Ten thrips species were associated with soybean plants in the field. The most abundant species was T. tabaci, average 256.5 average no.of individuals, followed by F. occidentalis (142.5 average no. of individuals), then N. variabilis (86.6/ average no. of individuals). Fourteen thrips species occurred on 5 legumes field crops and 41 weed plant species within soybean field. The highest average number 40.6.of individuals were recorded on Ammi majus. While the lowest one 3.3 average no. of individuals were on Urtica urens. Only 21diagnostic plant species were susceptible to infection with SVNV. G. max and Vigna radiate, were the highest percentage of infection 80% followed by V. unguilata & N. benthamiana, 75%. Egyptian isolate of Soybean vein necrosis virus (SVNV) in this study showed a high degree of similarity and it is closely related to TSWV from Egypt (DQ479968) and TCSV from USA (KY820965) with nucleotide sequence identity of 78%. Four thrips species transmitted SVNV (F. fusca 4.0%, F. schultzei 4.3%, F. tritici 3.3% and N. variabilis 68.0% transmission). Both C. phaseoli and M. sjostedti can acquire the virus but unable to transmit it. The following species; T. tabaci, F. occidentalis, S. dorsallis and T. palmi cannot acquire or transmit SVNV. The incidence of SVNV in the field started by the end of July then increased gradualy from 12.7 to 71.3% by the end of the season. In conclusion, few thrips individuals invaded soybean crops are enough to transmit high rate of SVNV within the crop. Furthermore, several vector species are also abundant on weeds, which are the major sources of soybean viruses transmitted to the crops. This information might be important for control and reduce the incidence of SVNV infection.
Highlights
Glycine max L. considered very important leguminous crop In Egypt, FAS Cairo forecasts that Egypt’s soybean area, as well as its production in marketing year 2017 & 2018, estimate of 9,000 hectares (HA) and 25,000 metric tons (MALR) and ARC (2019)
Molecular characterization and Incidence of (SVNV), Egypt were reared on cucumber while, Neohydatothrips variabilis were established on healthy soybean plants, F. occidentalis, F. schultzei, F. fusca, C. phasolii and M. sjostedti were reared on pods of French beans (Phaseolus vulgaris) in jars covered with thrips -proof -nets
The other species included F. fusca, F. tritici, C. phaseoli, S. dorsallis and T. palmi were recorded in low numbers, while the lowest was M. sjastedti (13.5/individual) Figure 1
Summary
Glycine max L. (soybean) considered very important leguminous crop In Egypt, FAS Cairo forecasts that Egypt’s soybean area, as well as its production in marketing year 2017 & 2018, estimate of 9,000 hectares (HA) and 25,000 metric tons (MALR) and ARC (2019). Tospoviruses, such as, Tomato spotted wilt virus (TSWV) It has a host range exceeding 1000 species in more than 100 plant families Parrella et al (2003) and Pappu et al (2009). Neohydatothrips variabilis (Beach) have been identified as the main vector of SVNV Zhou and Tzanetakis (2013), Abd El-Wahab and El-Shazly (2017). Both alternative weed hosts and thrips vector are the most sources of virus epidemiology, Groves et al (2002) and Okazaki et al (2011). 3- Throw the light on the reservoir hosts for both thrips and SVNV in field Such information is important to avoid damage to soybean crop
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