Genus Tetranychus Research Articles

GENETIC DIVERSITY OF MAJOR POLYPHAGOUS SPIDER MITE SPECIES ACROSS HOST PLANTS AND SPATIAL DISTRIBUTION

Different agroecosystems of southern Karnataka sampled for plant associated mites recorded six genera of tetranychid mites viz., Aponychus, Eutetranychus, Oligonychus, Petrobia, Schizotetranychus and Tetranychus. Neutrality test revealed a lowest haplotype diversity (0.993) of T. neocaledonicus population and Tajima’s D and Fu’s Fs test values were negatively significant for T. fijiensis, E. orientalis and S. baltazari populations, indicating the greater expansion of populations. Genetic analysis with ITS2 (rDNA) sequences revealed highest similarity between mite genera Petrobia and Aponychus showing lowest genetic distance of 0.51. Schizotetranychus has sister relationship with Eutetranychus which in turn clustered with Petrobia and Aponychus. Tetranychus and Oligonychus genera with lower genetic distance of 0.60 are clustered together. The study confirmed the clustering of morphologically related genera and lower genetic distances observed between related genera, expressed sister relationship. Molecular phylogenetic analysis of species under genus Oligonychus showed clustering in line with the morphology-based species taxonomic keys, while polyphagous species under the genus Tetranychus did not express form this grouping. Genetic diversity study of ten polyphagous mite species across their host plants and geographical occurrence revealed grouping according to locations in the phylogenetic tree. However, populations of Oligonychus tylus with a narrow host range showed close relationship for host plants than geographical locations which was evident in phylogenetic tree branching.

Phylogenetic-Related Divergence in Perceiving Suitable Host Plants among Five Spider Mites Species (Acari: Tetranychidae).

Simple SummaryMany spider mites are important agricultural pests in both fields and greenhouses worldwide and are diversified in their host plant range. How spider mites perceive their suitable host plants remains not completely clear. In this study, we found that spider mites cannot locate suitable host plants by volatile odours from a long distance, but they can use olfactory sensation in combination with gustatory sensation to make a precise selection for suitable host plants at a short distance. Highly polyphagous species showed strong sensitivity in sensing suitable host plants rather than the expected lowered sensitivity. We also found that the similarity among the five spider mite species in their performance in perceiving suitable host plants was highly correlated with their relative phylogenetic relationship.Spider mites belonging to the genus Tetranychus infest many important agricultural crops in both fields and greenhouses worldwide and are diversified in their host plant range. How spider mites perceive their suitable host plants remains not completely clear. Here, through two-host-choice designs (bean vs. tomato, and bean vs. eggplant), we tested the efficacies of the olfactory and gustatory systems of five spider mite species (T. urticae, T. truncatus, T. pueraricola, T. piercei, and T. evansi), which differ in host plant range in sensing their suitable host plant, by Y-tube olfactometer and two-choice disc experiments. We found that spider mites cannot locate their suitable host plants by volatile odours from a long distance, but they can use olfactory sensation in combination with gustatory sensation to select suitable host plants at a short distance. Highly polyphagous species displayed strong sensitivity in sensing suitable host plants rather than the lowered sensitivity we expected. Intriguingly, our principal component analyses (PCAs) showed that the similarity among five spider mite species in the performance of perceiving suitable host plants was highly correlated with their relative phylogenetic relationships, suggesting a close relationship between the chemosensing system and the speciation of spider mites. Our results highlight the necessity of further work on the chemosensing system in relation to host plant range and speciation of spider mites.

ИНСТРУМЕНТАЛЬНЫЙ ЭКОНОМИЧЕСКИЙ УРОВЕНЬ ПОВРЕЖДЕННОСТИ И ЭКОНОМИЧЕСКИЙ ПОРОГ ВРЕДОНОСНОСТИ ПОПУЛЯЦИЙ ПАУТИННОГО КЛЕЩА НА ЗЕМЛЯНИКЕ

Spider mites of the genus Tetranychus are universally one of the significant pests that damage garden strawberries and many other crops. One of the important problems of the pest population management is to be able to identify the thresholds of this pest, which, when feeding, causes a change in the color of plant leaves. Since it is very difficult to determine visually the level of leaf damage by spider mites, the authors of the study turned to the previously substantiated instrumental method for assessing damage using the relative electron transport rate (rETR) based on chlorophyll fluorescence detection in the leaf. Instrumental thresholds of pest damage were calculated: the economic injury level (EIL) and the economic threshold (ET). Studies were carried out in the laboratory on the leaves of strawberry grown in conteiners at temperature of 22 ± 2°C, relative humidity of 75 ± 10%, photoperiod (L : D) 16:8 h, as well as on the experimental plot of the strawberry plantation of JSC “Lenin Sovkhoz” (Moscow region); registration of the population dynamics of spider mites on the leaves being made. At the same time, using the JUNIOR-PAM fluorimeter (Heinz Walz, Germany), the dynamics of chlorophyll fluorescence in the leaves of the control (without mites) and experimental (damaged by mites) variants were measured. As a result, two varieties of industrial strawberries obtained a range of variation of the numerical physiological index, expressed in terms of the ratio of rETRmax between the experimental and control variants, equal to 1.4–2.0 conventional units, which corresponded to the economic injury level (EIL) of strawberry leaves. The latter trait was comparable to the same parameter obtained in the laboratory – 1.6. The economic threshold (ET), which signals the beginning of pesticide treatments, if it is reasonably expected that the number of pests will reach or exceed the value of EIL, also expressed in terms of the ratio of rETRmax between the experimental and control variants, turned out to be equal to 1.1–1.2 conventional units. The authors recommend using the proposed instrumental criteria for the harmfulness of the Atlantic spider mite on strawberries. We believe that this approach can be applied to other species of spider mites, as well as sucking insects.

Natural Enemies Associated with Brevipalpus sp. (Acari: Tenuipalpidae), Vector of Citrus Leprosis

Natural Enemies Associated with <i>Brevipalpus</i> sp. (Acari: Tenuipalpidae), Vector of Citrus Leprosis

The stimulatory effect of Chamaedorea radicalis ethanolic extract on Tetranychus merganser Boudreaux (Acari: Tetranychidae)

ABSTRACT The species of the genus Tetranychus Dufour are highly specialized pests that produce significant economic losses in crops. The red spider mite, Tetranychus merganser Boudreaux (Acari: Tetranychidae), is found in the United States, China, Mexico, and Thailand, and feeds on several plant species of economic importance. This study aimed to evaluate the effect of Chamaedorea radicalis Mart ethanol extract at different concentrations (5, 10, 50, 100, 250, 500, and 1000 µg/mL) on T. merganser adult females under laboratory conditions. The different concentrations did not cause mortality in T. merganser; but did have significant effects on female spider mites’ egg-laying, food intake, and demographic parameters. These effects require further study, since they can have considerable implications for natural enemies.

The microbiota in spider mite feces potentially reflects intestinal bacterial communities in the host.

Microorganisms provide many physiological functions to herbivorous hosts. Spider mites (genus Tetranychus) are important agricultural pests throughout the world; however, the composition of the spider mite microbial community, especially gut microbiome, remains unclear. Here, we investigated the bacterial community in five spider mite species and their associated feces by deep sequencing of the 16S rRNA gene. The composition of the bacterial community was significantly different among the five prevalent spider mite species, and some bacterial symbionts showed host-species specificity. Moreover, the abundance of the bacterial community in spider mite feces was significantly higher than that in the corresponding spider mite samples. However, Flavobacterium was detected in all samples, and represent a "core microbiome". Remarkably, the maternally inherited endosymbiont Wolbachia was detected in both spider mite and feces. Overall, these results offer insight into the complex community of symbionts in spider mites, and give a new direction for future studies.

Loop-mediated isothermal amplification combined with PCR for specific identification of injurious mite, Tetranychus urticae (Trombidiformes: Tetranychidae)

Identification of spider mites of the genus Tetranychus is strenuous due to their minute size and the restricted number of diagnostic characters. Most species of the Iranian Tetranychus spider mites are morphologically alike, distinguishable only based on male aedeagus; however, most of the intercepted Tetranychus specimens are females, leaving their identification at the genus level. Tetranychus urticae is a highly polyphytophagous pest species commonly found in greenhouses of Iran. As the unambiguous identification of a pest is the first crucial step toward implementing any effective pest management procedure, various DNA-based methods have formerly been used as complement to the traditional morphological methods. In the current study, a technique integrating loop-mediated isothermal amplification (LAMP) with PCR (polymerase chain reaction) was utilized for quick detection of T. urticae and discriminating it from other Tetranychus species attacking greenhouse crops. The assay was validated against various developmental stages of T. urticae specimens. Not only did the PCR-LAMP assay decrease the time needed for identification, but also was species-specific and sensitive enough to be applied even by non-specialists.

Spider mites (Acari: Tetranychidae) of Saudi Arabia: two new species, new records and a key to all known species

ABSTRACTA total of 18 spider mite species belonging to 10 genera of the family Tetranychidae (Acari: Prostigmata) are reported from different provinces of Saudi Arabia (SA). Among these, two new species, Sonotetranychus madinahensis sp. nov. and Tetranychus salicornicus sp. nov., belonging to the subfamily Tetranychinae are described and illustrated. Also, five genera and 11 species are new to the mite fauna of SA. The distribution and host data of all recorded species in the current study are provided. A key to all spider mite species of SA is provided as well as a key to the species of the armenychus species group of the genus Tetranychus Dufour, based on males.www.zoobank.org/urn:lsid:zoobank.org:pub:C41BB3ED-99D5-4DCF-B557-09526FA7D56B

Development of microsatellite markers for six Tetranychus species by transfer from Tetranychus urticae genome

Microsatellite markers are frequently used to explore the population genetic structure of organisms. Spider mites (genus Tetranychus) are important agricultural pests. Several markers have been developed for T. urticae, but for other spider mites, few such markers are available, hampering studies of their population genetics. In this study, we developed and characterized microsatellite markers for six non-model spider mite species (T. truncatus, T. kanzawai, T. ludeni, T. piercei, T. phaselus and T. pueraricola) by cross-species amplification of markers in the T. urticae genome, in order to better understand the population structure of Tetranychus species. Among 228 screened loci, many were polymorphic, including 13 loci in T. urticae, 11 loci in T. truncatus, 15 loci in T. pueraricola, 23 loci in T. kanzawai, 19 loci in T. piercei, 11 loci in T. phaselus and 9 loci in T. ludeni. Sequence analysis determined that the fragment length variations of the transferred microsatellites were mainly due to the variations of the numbers of repeats. These new microsatellite markers should be useful for studying the population genetics of the seven Tetranychus species.

Development of species‐specific primers for rapid diagnosis of Tetranychus urticae, T. kanzawai, T. phaselus and T. truncatus (Acari: Tetranychidae)

AbstractSpecies diagnosis is of the utmost importance to both pest management and plant quarantine services. Because of difficulties in the morphological diagnosis of spider mites, molecular techniques are of great value to rapidly and accurately diagnose closely related species. We examined four species of genus Tetranychus (the green and red forms of T. urticae, and T. kanzawai, T. phaselus and T. truncatus), which are found in Korea and are of significance to plant quarantine services. DNA samples isolated from a single egg, larva or adult weighed 64–188 ng. We designed species‐specific primers by performing sequence alignment for 107 sequences of the ribosomal internal transcribed spacer 2 (ITS2) region, which we obtained from GenBank, and sequences generated in this study. Specific nucleotides of each species were selected for designing primers specific for each species. Each species‐specific primer pair, when used to perform PCR analyses, detected only the species from which it originated. However, a T. urticae‐specific primer pair did not discriminate between the green and red forms of this species. These species‐specific primers can be applied in practice for the rapid and accurate diagnosis of spider mite species in plant quarantine and in agricultural fields.

Development and Validation of a Real-Time PCR Assay for Rapid Detection of Two-Spotted Spider Mite, Tetranychus urticae (Acari: Tetranychidae).

Spider mites of the genus Tetranychus are difficult to identify due to their limited diagnostic characters. Many of them are morphologically similar and males are needed for species-level identification. Tetranychus urticae is a common interception and non-regulated pest at New Zealand’s borders, however, most of the intercepted specimens are females and the identification was left at Tetranychus sp. Consequently, the shipments need to be fumigated. DNA sequencing and PCR-restriction fragment length polymorphism (PCR-RFLP) protocols could be used to facilitate the accurate identification. However, in the context of border security practiced in New Zealand, insect identifications are required to be provided within four hours of receiving the samples; thus, those molecular methods are not sufficient to meet this requirement. Therefore, a real-time PCR TaqMan assay was developed for identification of T. urticae by amplification of a 142 bp Internal Transcribed Spacer (ITS) 1 sequence. The developed assay is rapid, detects all life stages of T. urticae within three hours, and does not react with closely related species. Plasmid DNA containing ITS1 sequence of T. uritcae was serially diluted and used as standards in the real-time PCR assay. The quantification cycle (Cq) value of the assay depicted a strong linear relationship with T. urticae DNA content, with a regression coefficient of 0.99 and efficiency of 98%. The detection limit was estimated to be ten copies of the T. urticae target region. The assay was validated against a range of T. urticae specimens from various countries and hosts in a blind panel test. Therefore the application of the assay at New Zealand will reduce the unnecessary fumigation and be beneficial to both the importers and exporters. It is expected that the implementation of this real-time PCR assay would have wide applications in diagnostic and research agencies worldwide.

Altered volatile profile associated with precopulatory mate guarding attracts spider mite males.

Proximate factors affecting animal behavior include stimuli generated by conspecifics. In spider mites of the genus Tetranychus (Acari: Tetranychidae), males guard pre-reproductive quiescent females, because only the first mating results in fertilization. In a dual-choice experiment, more adult males of T. urticae were attracted to females guarded by a male than to solitary females. Because spider mites are known to perceive volatiles, we hypothesized that guarded and solitary females differ in the volatile blends emitted. To test this hypothesis, headspace volatiles of guarded females, solitary females, and solitary males were collected, respectively. GC/MS analysis detected octanal, methyl salicylate, ethyl 4-ethoxybenzoate, and methyl cis-dihydrojasmonate in all of the groups. Orthogonal Projection to Latent Structures Discriminant Analysis (OPLS-DA) of the blends clearly discriminated guarded females from solitary females, supporting our hypothesis. Individual compounds did not show significant difference in emission rates for guarded females vs. solitary females, suggesting that differences lay in the total blend composition. OPLS-DA did not discriminate between the blends emitted by guarded females and solitary males. In conclusion, the differences in the volatile blends are likely to mediate male discrimination between guarded and solitary females.

A new Tetranychus Dufour (Acari: Tetranychidae) associated withSolanaceae from Turkey

A new plant-feeding mite species, Tetranychus solanacearum Cobanoglu and Ueckermann sp. Nov. (Acari: Tetranychidae), is described and illustrated. The samples were collected from various solanaceous plants (Solanaceae) [black nightshade (Solanum nigrum L.), bittersweet nightshade (Solanum dulcamara L.), eggplant (Solanum melongena L.), spiny nightshade (Solanum rostratum Dunal), jimsonweed or datura (Datura stramonium L.), and tomato (Lycopersicon esculentum L.)] in Ankara Province, Turkey. A key to all species of the genus Tetranychus Dufour known to occur in Turkey is presented in the paper.

The complete mitochondrial genomes of six species of Tetranychus provide insights into the phylogeny and evolution of spider mites.

Many spider mites belonging to the genus Tetranychus are of agronomical importance. With limited morphological characters, Tetranychus mites are usually identified by a combination of morphological characteristics and molecular diagnostics. To clarify their molecular evolution and phylogeny, the mitochondrial genomes of the green and red forms of Tetranychus urticae as well as T. kanzawai, T. ludeni, T. malaysiensis, T. phaselus, T. pueraricola were sequenced and compared. The seven mitochondrial genomes are typical circular molecules of about 13,000 bp encoding and they are composed of the complete set of 37 genes that are usually found in metazoans. The order of the mitochondrial (mt) genes is the same as that in the mt genomes of Panonychus citri and P. ulmi, but very different from that in other Acari. The J-strands of the mitochondrial genomes have high (∼84%) A+T contents, negative GC-skews and positive AT-skews. The nucleotide sequence of the cox1 gene, which is commonly used as a taxon barcode and molecular marker, is more highly conserved than the nucleotide sequences of other mitochondrial genes in these seven species. Most tRNA genes in the seven genomes lose the D-arm and/or the T-arm. The functions of these tRNAs need to be evaluated. The mitochondrial genome of T. malaysiensis differs from the other six genomes in having a slightly smaller genome size, a slight difference in codon usage, and a variable loop in place of the T-arm of some tRNAs by a variable loop. A phylogenic analysis shows that T. malaysiensis first split from other Tetranychus species and that the clade of the family Tetranychoidea occupies a basal position in the Trombidiformes. The mt genomes of the green and red forms of T. urticae have limited divergence and short evolutionary distance.

New species and new records of Tetranychidae (Acarina, Prostigmata) from Thailand.

Sampling efforts conducted in several provinces from Thailand disclosed three new species of tetranychid mites. Two of them belong to the genus Tetranychus, namely Tetranychus occultaspina sp. nov. and Tetranychus truncatissimus sp. nov. and the third species belongs to the genus Schizotetranychus, Schizotetranychus krungthepensis sp. nov. They were collected on Ipomoea aquatica, Bambusa multiplex and Saccharum officinarum, respectively. New records and new hosts are also mentioned.

PM 7/116 (1)Tetranychus evansi

PM 7/116 (1)<i>Tetranychus evansi</i>

DNA-Based Identification of Spider Mites: Molecular Evidence for Cryptic Species of the Genus &lt;I&gt;Tetranychus&lt;/I&gt; (Acari: Tetranychidae)

Spider mites are difficult to identify because they are very small and have a limited number of diagnostic characters. Most species of the spider mite genus Tetranychus in Japan are morphologically similar, differing only in the diameter of the aedeagal knob in males. Because this genus contains many important pests, the unambiguous identification of species is crucial for effective pest management and quarantine procedures. DNA-based methods could complement the morphological methods. We examined whether Tetranychus species in Japan could be identified by DNA sequences using the internal transcribed spacer region of nuclear ribosomal DNA and the cytochrome c oxidase subunit I gene of mitochondrial DNA. We determined sequences of the 13 known Tetranychus species in Japan. We could identify 10 of the 13 species in the internal transcribed spacer tree. In the cytochrome c oxidase subunit I tree, we could identify all 13 known Tetranychus species in Japan. Although Tetranychus kanzawai Kishida and T. parakanzawai Ehara were identified by DNA sequences, they were clearly separated into two monophyletic clades each, indicating that a cryptic species existed in each species.

Identification and molecular phylogeny of agriculturally important spider mites (Acari: Tetranychidae) based on mitochondrial and nuclear ribosomal DNA sequences, with an emphasis on Tetranychus

Tetranychid mites are serious agricultural pests. Identification of species in the Tetranychidae is hampered by their close morphological similarities, especially for species within the genus Tetranychus. In this study, we examined the relationships of nine agriculturally important species in the Tetranychidae from China based on mitochondrial (cytochrome c oxidase subunit 1) and nuclear (internal transcribed spacer 1 and 2 of ribosomal RNA gene) sequences. The results confirm the monophyly of the morphologically defined Tetranychus, Panonychus, Amphitetranychus and Petrobia. However the position of Amphitetranychus viennensis within the Tetranychidae needs to be confirmed. The genetic distances between Tetranychus truncatus, T. turkestani and T. urticae that their taxonomy needs revision. In particular, both cytochrome oxidase 1 and the internal transcribed spacers 1 and 2 of rDNA sequences showed large geographical differences within T. cinnabarinus, suggesting the existence of cryptic species within this species.

Reproductive performance of seven strains of the tomato red spider mite Tetranychus evansi (Acari: Tetranychidae) at five temperatures

The tomato red spider mite Tetranychus evansi Baker et Pritchard occurs on solanaceous plants, and causes serious damage to a variety of crops in Africa and Europe. In 2001 this species was also found in Japan, on nightshade (Solanum nigrum L.), and its invasion to solanaceous of agricultural importance is feasible. To evaluate its potential severity as a pest, the present study assessed the life-history parameters, such as the rate of development and the intrinsic rate of natural increase (r(m)), on S. nigrum for T. evansi collected on seven sites worldwide. Increasing temperatures between 15 and 32.5°C significantly increased the developmental rate of the seven strains while immature developmental duration was about the same at 32.5-40°C. The rate of egg-to-adult development [(% hatch) × (% survival)] exceeded 88% at temperatures between 15 and 37.5°C. The lower thermal thresholds (LT) were 11.9-12.5°C for both egg-to-adult and egg-to-egg development. The optimum developmental temperatures ranged from 36.7 to 43.8°C and the upper developmental threshold (UT) ranged from 45.2 to 59.4°C. The r (m)-values became higher with temperature increasing from 15 to 35°C. The r (m)-values at 25°C ranged from 0.265 to 0.277 which are relatively high for species of the genus Tetranychus. These results indicate that T. evansi after invasion into Japan has the potential to become a serious pest on solanaceous crops, just the same as in Africa and Europe.

Description of a new Tetranychus (Acarina, Prostigmata: Tetranychidae) pest of Musa from French Guiana

A new species of tetranychid mite, genus Tetranychus Dufour, 1832, is described and illustrated herein from neotropical area. Tetranychus musae sp. nov. (Acari, Prostigmata: Tetranychidae) differs from other species in the genus by the combination between the arrangement of leg setae on females tarsus I and the shape of the aedeagus. Tarsus I bears one tactile setae proximal to proximal duplex setae and three tactiles in line or almost in line with proximal duplex setae. The aedeagus knob consists of an acute posterior projection bent ventrally and a larger anterior rounded projection directed anterodorsally. T. musae specimens were collected in French Guiana where they appeared to be a pest of Musa sp. A key to adults of neotropical species of the genus Tetranychus feeding on banana is provided.