Molecular characterization and incidence of new tospovirus: Soybean Vein Necrosis Virus (SVNV) in Egypt

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.

Problems with the Concept of “Pest” among the Diversity of Pestiferous Thrips

Almost all of the thrips species that are considered pests are members of a single subfamily of Thripidae, the Thripinae, a group that represents less than 30% of the species in the insect Order Thysanoptera. Three of the five major Families of Thysanoptera (Aeolothripidae, Heterothripidae, Melanthripidae) are not known to include any pest species. The Phlaeothripidae that includes more than 50% of the 6300 thrips species listed includes very few that are considered to be pests. Within the Thripidae, the members of the three smaller subfamilies, Panchaetothripinae, Dendrothripinae and Sericothripinae, include remarkably few species that result in serious crop losses. It is only in the subfamily Thripinae, and particularly among species of the Frankliniella genus-group and the Thrips genus-group that the major thrips species are found, including all but one of the vectors of Orthotospovirus infections. It is argued that the concept of pest is a socio-economic problem, with the pest status of any particular species being dependent on geographical area, cultivation practices, and market expectations as much as the intrinsic biology of any thrips species.

Alfa and beta diversity of thrips (Thysanoptera) and biological control agents in chrysanthemum flowers (Chrysanthemum sp.) of two ecoregions in Jujuy province, Argentina

The objectives of this study are to identify thrips and their biological controllers, to analyze their abundance in three flower opening stages stages of chrysanthemum crops, and to determine alpha and beta diversity in two ecoregions of Jujuy province (Argentina). The study was carried out in the Chaco ecoregion (ECH) in October and November 2016, and in the Prepuna ecoregion (EP) in February and March 2018. On each date, six replicates of five flowers were excised in the stages: flower bud , semi-open flower and open flower. Diversity profiles and rank-abundance curves were built, and Jaccard's coefficient of similarity was applied. The diversity profiles showed significant differences in thrips communities. In the ECH, 15 thrips species were identified; the dominant and permanent species were Microcephalothrips abdominalis (Crawford) and Frankliniella occidentalis (Pergande). Five species were recorded in the EP, although Frankliniella gemina Bagnall and Thrips tabaci Lindeman on their own represented 78% of the total abundance. In the ECH, 20 entomophagous species/morphospecies were recognized, and 19 in the EP; antocorids were dominant in both ecoregions. The thrips and the entomophagous communities of chrysanthemum flowers were different (34%) between the ecoregions studied.

Analysis of thrips (Thysanoptera: Thripidae) diversity in avocado shows the presence of a new species and limitations of using the COI gene for differentiation of two species

Thrips are important pests of avocados causing damage to the fruits, making themunsuitable for exportation. Many of them are quarantine species and their identification isnecessary. Despite their importance, not many studies describe thrips diversity on avocado,especially in Colombia, partly because identification of some of the species is difficult usingclassical taxonomic keys. In this study, 93 adult thrips specimens were collected on avocadoand adventitious dandelion plants from plantations in the department of Antioquia, Colombia. Morphological characters were used to classify 62 of them and all of them were analyzed by PCR amplification and sequencing of cytochrome c oxidase subunit I (COI) gene and internal transcribed spacer (ITS) region. The species identified by morphological features were Frankliniella gardeniae Moulton, F. gossypiana Hood, F. panamensis Hood, Liothrips perseae Watson, Thrips palmi Karny, T. simplex (Morison), T. trehernei Priesner, Microcephalothrips abdominalis (Crawford DL), and Scirtothrips hansoni Mound & Hoddle (Tubulifera), being F. panamensis, M. abdominalis, and S. hansoni reported for the first time on avocado in Colombia. Thrips simplex and T. trehernei were also found on adventitious dandelion plants, but not on avocado. Phylogenetic analysis of COI and ITS sequences showed that most species, except for F. gardeniae and F. gossypiana were mainly identified with the COI gene. Furthermore, FST values obtained between them suggest no genetic differentiation at COI level. The results obtained here contribute to the knowledge of the diversity of thrips species found on the avocado crop in Colombia and are meaningful for pest management.

Checklist of the suborder Terebrantia (Thysanoptera): generic diversity and species composition in Xishuangbanna, Yunnan Province, China

Thysanoptera is amongst the most predominant orders of insects in different ecological zones with worldwide distribution. Due to their small size, there is a large gap in their distribution and host range data. To the best of our knowledge, there is no investigation on the thrips distribution and their host range in Xishuangbanna. Currently, a total of 566 species in 155 genera are listed in China, of which 313 species represent Terebrantia. In this study, a list of 116 species representing 55 genera within the families Aeolothripidae and Thripidae is provided. Two of these, Dichromomothrips nakahari Moud, 1976 (subfamily Thripinae) and Phibalothrips rugosus Kudo, 1979 (subfamily Panchaetothripinae) are recorded for the first time in China. Thrips species with their host ranges, habits and habitats are provided. Our study aims to contribute to the global biodiversity distribution data-gap of Thysanoptera for conservation purposes, as well as pest species targetting Integrated Pest Management tactics.

Frontiers Approaches to the Diagnosis of Thrips (Thysanoptera): How Effective Are the Molecular and Electronic Detection Platforms?

Thrips are insect pests of economically important agricultural, horticultural, and forest crops. They cause damage by sucking plant sap and by transmitting several tospoviruses, ilarviruses, carmoviruses, sobemoviruses, and machlomoviruses. Accurate and timely identification is the key to successful management of thrips species. However, their small size, cryptic nature, presence of color and reproductive morphs, and intraspecies genetic variability make the identification of thrips species challenging. The use of molecular and electronic detection platforms has made thrips identification rapid, precise, sensitive, high throughput, and independent of developmental stages. Multi-locus phylogeny based on mitochondrial, nuclear, and other markers has resolved ambiguities in morphologically indistinguishable thrips species. Microsatellite, RFLP, RAPD, AFLP, and CAPS markers have helped to explain population structure, gene flow, and intraspecies heterogeneity. Recent techniques such as LAMP and RPA have been employed for sensitive and on-site identification of thrips. Artificial neural networks and high throughput diagnostics facilitate automated identification. This review also discusses the potential of pyrosequencing, microarrays, high throughput sequencing, and electronic sensors in delimiting thrips species.

Checklist of order Terebrantia (Thysanoptera): generic diversity and species composition in Xishuangbanna, Yunnan province, China

Thysanoptera is one of the most predominant order of insects in different ecological zones with worldwide distribution. Due to their small size there is a big gap in their distribution and host range data. To the best of our knowledge there is no investigation on thrips distribu+tion and host range in Xishuangbanna. Currently, a total 566 species in 155 genera are listed in China, of which 313 species represent Terebrantia. In this study, a list of 115 species representing 54 genera within 2 families (Aeolothripidae & Thripidae) is provided.Two of these, Dichromomothrips nakahari Moud, 1976 (Subfamily: Thripinae) and Phibalothrips rugosus Kudo, 1979 (Subfamily: Panchaetothripinae) are newly recorded in China. Thrips species with their host ranges, habits, and habitats are provided. Our study will contribute to the global biodiversity distribution data-gap of Thysanoptera.

Characterization of E93 in neometabolous thrips Frankliniella occidentalis and Haplothrips brevitubus

Insect metamorphosis into an adult occurs after the juvenile hormone (JH) titer decreases at the end of the juvenile stage. This generally coincides with decreased transcript levels of JH-response transcription factors Krüppel homolog 1 (Kr-h1) and broad (br), and increased transcript levels of the adult specifier E93. Thrips (Thysanoptera) develop through inactive and non-feeding stages referred to as “propupa” and “pupa”, and this type of distinctive metamorphosis is called neometaboly. To understand the mechanisms of hormonal regulation in thrips metamorphosis, we previously analyzed the transcript levels of Kr-h1 and br in two thrips species, Frankliniella occidentalis (Thripidae) and Haplothrips brevitubus (Phlaeothripidae). In both species, the transcript levels of Kr-h1 and br decreased in the “propupal” and “pupal” stages, and their transcription was upregulated by exogenous JH mimic treatment. Here we analyzed the developmental profiles of E93 in these two thrips species. Quantitative RT-PCR revealed that E93 expression started to increase at the end of the larval stage in F. occidentalis and in the “propupal” stage of H. brevitubus, as Kr-h1 and br mRNA levels decreased. Treatment with an exogenous JH mimic at the onset of metamorphosis prevented pupal-adult transition and caused repression of E93. These results indicated that E93 is involved in adult differentiation after JH titer decreases at the end of the larval stage of thrips. By comparing the expression profiles of Kr-h1, br, and E93 among insect species, we propose that the “propupal” and “pupal” stages of thrips have some similarities with the holometabolous prepupal and pupal stages, respectively.

Mating behaviour, mate choice and female resistance in the bean flower thrips (Megalurothrips sjostedti)

Many species of thrips (Thysanoptera) in the family Thripidae form mating aggregations, but the adaptive significance of these aggregations and the extent of male and female mate choice is poorly understood. We studied the mating behaviour of the bean flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), which forms male aggregations and occurs across sub-Saharan Africa. We tested whether males choose mates by female age or mating status. No-choice mating bioassays with one male and one female were used to simulate the way males usually encounter only one female at a time in aggregations in the field. Virgin females violently resisted mating attempts by males, but we found no compelling evidence to establish whether this was indiscriminate or was screening suitable males. Younger males (1–2 days old) did not discriminate females by age (1–2 or 7–10 days old), but older males (7–10 days old) avoided mating with older females. Any male choice by female mating status (virgin or mated) was weak or absent. The mating behaviour of M. sjostedti shows broad similarities with that of other thrips species that form aggregations, but also shows some distinct and novel differences, which can help our understanding of the adaptive significance of aggregations.