Arrhenotokous and thelytokous populations of Thrips tabaci from tobacco or leek plants were evaluated for their ability to transmit Tomato spotted wilt virus (TSWV) and for their host preference. Transmission efficiencies were comparatively studied using leaf disks of Petunia hybrida, Datura stramonium, and Nicotiana tabacum cv. Basmas. Adults of arrhenotokous populations collected on infected tobacco plants in the field were efficient transmitters (up to 48.5% transmission) and remained so when maintained on tobacco for several generations. Arrhenotokous T. tabacipopulations from leek plants were poor transmitters (up to 3.1% transmission), whereas no transmission was obtained with thelytokous populations from leek. All populations could infest leek, however none of the arrhenotokous and thelytokous populations from leek plants was able to infest tobacco. TSWV could be acquired by both first and second larval instars of a T. tabacipopulation from tobacco. However, the transmission by adults decreased with the age at which the virus was acquired by larvae. The highest efficiencies (61% of males and 51% of females transmitted) were obtained when newborn (0- to 24-h old) larvae acquired the virus. The majority of thrips started to transmit after becoming adult and rates were positively correlated with the temperature at which the thrips were kept. The median latent period values found for adults decreased with increasing temperature. The median acquisition access period (AAP50) of the population was 41 min, whereas the AAP₅₀ was 65 min for males and 35 min for females. The median inoculation access period of males was 246 and 365 min on tobacco and petunia, respectively, and 96 and 345 min for females. The results show that T. tabaci forms a complex in terms of host preference, reproductive strategy, and ability to transmit TSWV. The transmission parameters show that the thrips of arrhenotokous populations infesting tobacco are highly efficient vectors.

The transmission of tomato spotted wilt tospovirus (TSWV) by Thrips tabaci collected from leek was studied using the petunia local‐lesion leaf‐disc assay. After an acquisition‐access period of 72 h given to newborn larvae up to 8 h old, the efficiency of transmission by adults was determined in three inoculation‐access periods of 48 h. This efficiency varied for six T. tabaci populations from 0.7 to 11.6% in experiments using the Greek TSWV isolate GR‐04. Males were more efficient transmitters than females (19 out of 176 versus five out of 494). Frankliniella occidentalis transmitted the same virus with a higher efficiency (34.8%). The transmission rate differed also among TSWV isolates, as shown in tests with four T. tabaci using two isolates. The virus was more efficiently acquired from infected leaf material of Datura stramonium than from that of Emilia sonchifolia . Plants of the latter species were more susceptible than Nicotiana tabacum in thrips transmission tests.

A survey was conducted in the Macedonia region of Greece to determine the reservoir hosts of Tomato spotted wilt virus (TSWV) in three tobacco fields and in a greenhouse complex in which lettuce and the ornamentals chrysanthemum, gerbera, aster, and anemone were grown. Assays for TSWV infection were made by enzyme-linked immunosorbent assay on 6,172 plant samples, 3,909 from tobacco fields and 2,263 from the greenhouse complex, comprising plants of 208 species in 137 genera of 42 families. Plants of 86 species out of 63 genera of 27 families were infected of which 39 species are newly reported hosts of TSWV. An infection index was developed to evaluate the relative potential of each weed species as a virus source in both systems. Seventeen species in the tobacco fields and nine in the greenhouses had an infection index higher than one. Most species with infected plants were found in the Compositae family. Plants of some species occurring both in tobacco fields and in greenhouses were infected at only one of these sites. Frankliniella occidentalis was the common thrips species on weeds and crops in the greenhouses, while Thrips tabaci was the only vector on tobacco plants and weeds in the tobacco fields. This observation strongly suggests that the occurrence of species with infected plants and their number have to be attributed to the vector species prevailing in the greenhouse complex or tobacco fields, supporting the conclusion that TSWV is spread in two different epidemiological processes in Greece.

Legumes, one of the most important sources of human food and animal feed, are known to be susceptible to a plethora of plant viruses. Many of these viruses cause diseases which severely impact legume production worldwide. The causal agents of some important virus-like diseases remain unknown. In recent years, high-throughput sequencing technologies have enabled us to identify many new viruses in various crops, including legumes. This review aims to present an updated list of legume-infecting viruses. Until 2020, a total of 168 plant viruses belonging to 39 genera and 16 families, officially recognized by the International Committee on Taxonomy of Viruses (ICTV), were reported to naturally infect common bean, cowpea, chickpea, faba-bean, groundnut, lentil, peas, alfalfa, clovers, and/or annual medics. Several novel legume viruses are still pending approval by ICTV. The epidemiology of many of the legume viruses are of specific interest due to their seed-transmission and their dynamic spread by insect-vectors. In this review, major aspects of legume virus epidemiology and integrated control approaches are also summarized.