Replication of euchromatin and heterochromatin in a mealybug

Asynchronous DNA replication of euchromatic (E) and heterochromatic (H) chromosomes and heterochromatic B chromosomes (B) were studied in the mealybug, Pseudococcus obscurus Essig (Homoptera: Coccoidea). The study was carried out on mycetocytes of adult females and on spermatocytes of mid-second instar males by employing tritiated thymidine labeling and autoradiography. In the mycetocytes the incorporation of the labeled thymidine began and ended later in the B's than in the E chromosomes. The S period was found to be about 21 hours. The DNA replication of the E chromosomes occupied about 86% of the S period and that of the B's 33%; during 18% of the mid-S period the replication of the two types of chromosomes overlapped. In the meiotic S period of the spermatocytes, the DNA of the E chromosomes started to replicate earlier than that of the H chromosomes and the B's, but the replication of the E chromosomes, the H chromosomes, and the B's overlapped. The H chromosomes completed their replication much later than the E chromosomes and slightly later than the B's.Supported by grants GB 1585 and GB 6745 to Dr. Uzi Nur from the National Science Foundation, Washington, D. C.Part of a thesis submitted to the University of Rochester in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

Germline cyst development and imprinting in male mealybug <Emphasis Type="Italic">Planococcus citri</Emphasis>

In the epigenetic modifications involved in the phenomenon of imprinting, which is thought to take place during gametogenesis, one of the primary roles is exerted by histone tail modifications acting on chromatin structure. What is more, in insects like mealybugs, with a lecanoid chromosome system, imprinting is strictly related to sex determination. In many diverse species gametes originate in specific, highly evolutionarily conserved structures called germline cysts. The use of staining techniques specific for fusomal components like F-actin has allowed us to describe for the first time the morphogenesis of male germline cysts in the mealybug Planococcus citri. Antibodies to anti-methylated lysine 9 of histone H3 (MeLy9-H3) and anti-heterochromatin protein 1 (HP1) were used during cyst formation to investigate the involvement of these epigenetic modifications in the phenomenon of imprinting and their possible concerted action in sex determination in P. citri. These observations indicate: (i) a specific role for F-actin in the segregation, typical of the lecanoid chromosome system, of genomes of paternal origin; (ii) that the two vital gametes originating from a given meiosis, although carrying the same genome, differ in the levels of both MeLy9-H3 and HP1, one of them being more heavily labelled by both antibodies.     

警惕一种危险性绵粉蚧入侵中国

绵粉蚧Phenacoccus solenopsis Tinsley是一种危害园林、水果、大田作物的害虫。该虫已经传入巴基斯坦、印度,2005年以来在巴基斯坦大部分棉区暴发成灾,已经对我国构成威胁。本文概括介绍了该虫寄主范围及经济重要性、生物学、传播方式等,并对该虫对中国的潜在威胁作了简要分析。     

RNA synthesis and heterochromatization in early development of a mealybug

Microinjection of specific radioisotope tracers showed that DNA and protein synthesis are triggered by fertilization but nuclear RNA synthesis does not occur until the cleavage nuclei migrate to the periphery. In the male, heterochromatization of the paternal chromosome set also occurs when the cleavage nuclei reach the periphery. These results help to explain those of several types of genetic test, especially the failure of typical dominant lethal induction in the heterochromatized set.     

Inventory and abundance of mealybug species in immature and mature cocoa farms in Côte d'Ivoire

From 2013 to 2018, surveys were conducted in counties not previously surveyed in order to determine species of mealybugs present in the cocoa orchard in Côte d'Ivoire as well as their abundance according to the age of cocoa trees. Immature and mature cocoa trees were inspected to hand‐height in 5 and 29 counties infected with Cacao swollen shoot virus (CSSV). In each cocoa farm, mealybugs were searched for on fruits, leaves, flowers, twigs and trunks. Mealybug species were identified, and colonies were counted. Five mealybug species were identified on immature cocoa trees: Ferrisia virgata, Formicococcus njalensis, Planococcus citri, Planococcus kenyae and Pseudococcus longispinus. In addition to these species, four species, Dysmicoccus brevipes, Maconellicoccus hirsutus, Phenacoccus hargreavesi and Pseudococcus jackbeardsleyi were identified on mature cocoa trees. On immature cocoa trees, Fo. Njalensis, Pl. citri and Ps. longispinus comprised were, respectively, 35%, 33% and 19% of colonies, respectively. On mature cocoa trees, Fo. Njalensis and Pl. citri comprised 63.2% and 21.0%, and others species 15.8%. Nevertheless, the abundance of mealybug species varied according to the age of cocoa trees. The preferred organs of mealybugs were pods (74.1%) followed by twigs (13.4%) and flowers (7.4%). Previously, the mealybug Paracoccus burnerae (Brain) was found on Theobroma cacao, which is the first record for this species in Côte d'Ivoire and on this host‐plant.     

Endocrocin and its derivatives from the Japanese mealybug Planococcus kraunhiae

The Japanese mealybug, Planococcus kraunhiae, is suitable as a model insect for biosynthetic studies on mealybug pigments. Four yellow pigments, including two novel ones, were isolated from the mealybug bodies and characterized as endocrocin, a dicarboxylic acid named fujikonaic acid (1), emodin 1-O-β-D-glucopyranoside and 7-hydroxyemodin 1-O-β-D-glucopyranoside (2). The enzymatic activity of emodin 1-O-glucosyltransferase was observed in the extracts of insect bodies.     

扶桑绵粉蚧的过冷却点和体液结冰点测定

本文测定了扶桑绵粉蚧Phenacoccus solenopsis Tinsley除卵期以外其它各虫态的过冷却点和结冰点.结果表明,该虫过冷却点以1龄若虫最低,为-24.02℃;雄虫预蛹次之,为-22.13℃;雄虫蛹、雄虫2龄若虫、雌虫3龄若虫、雄成虫、雌虫2龄若虫、雌成虫过冷却点逐渐升高,分别为-21.08℃、-20.25℃、-19.05℃、-18.42℃、-17.91℃、-16.89℃.体液结冰点也以1龄若虫最低,为-23.2℃;雄虫预蛹次之,为-19.09℃;雄虫蛹、雄虫2龄若虫、雌虫3龄若虫、雌虫2龄若虫、雌成虫、雄成虫体液结冰点逐渐升高,分别为-16.64%、-15.81℃、-13.92℃、-13.20℃、-12.85℃、-12.79℃.试验结果表明扶桑绵粉蚧过冷却点低,耐寒性较强,可能适宜在中国北部更广泛的区域生存.     

Comparison of mealybug (Planococcus lilacinus) and fruit fly genomes: isolation and analysis of conserved sequences and their utility in studying synteny in the mealybug

By using ligation-mediated PCR products from mealybug DNA as tester and biotinylated fly DNA as driver, we recovered a fraction of the tester that remains hybridized to driver following high-stringency washing conditions. This fraction is expected to contain mealybug sequences conserved in the fly (MCF). Reciprocal experiments enabled the isolation of fly sequences conserved in the mealybug (FCM). Coding sequences among MCF show amino acid identities >40% with fly proteins, allowing a reliable identification of orthologs. Three sequences from the fly cytogenetic positions 98-99 were hybridized onto mealybug chromosomes and the results identified differences in synteny between the two species. Taken together, our results present a method for direct isolation of sequences conserved between an 'orphan' (mealybug) genome and a 'reference' (fly) genome and showed that these sequences can be used to study chromosome synteny in the mealybug.     

棉花粉蚧雄成虫对雌虫的性选择及日交配节律

研究棉花粉蚧雄成虫对不同虫态、不同日龄雌虫的性选择以及雌雄成虫日交配节律,为该虫性信息素的研究提供科学依据。采用四臂嗅觉仪测定了雄虫对不同虫态以及不同日龄雌虫(3龄若虫、1日龄至8日龄处女雌成虫、已交配雌成虫)的选择性,观察了雄虫与雌成虫日交配节律。结果表明,雄成虫对4日龄处女雌成虫的选择率显著高于其他虫态和日龄,一天内扶桑绵粉蚧交配高峰期出现在7∶00-9∶00。因此,推测4日龄处女雌成虫和上午7∶00-9∶00可能是释放性外激素的旺盛虫期和时间。     

Vine mealybug sex pheromone increases citrus mealybug parasitism by Anagyrus sp. near pseudococci (Girault)

The present study was aimed at elucidating the role of lavandulyl senecioate (LS), the sex pheromone of Planococcus ficus, in host selection of the parasitoid Anagyrus sp. near pseudococci. Field trials were carried out in Portugal, Italy and Israel. The effect of LS on the parasitism rate of the wasp was determined by exposing sentinel mealybugs combined with pheromone dispensers impregnated with LS, in comparison with other baits: lavandulyl isovalerate (LI); planococcyl acetate (PAc); and unbaited control traps. In addition, in order to study the host location behavior of A. sp. near pseudococci, pheromone dispensers were placed at three different distances: inside the trap, 30 or 60 cm away from the trap. The number of parasitoid females inside the traps, the number of parasitized mealybugs, and the number of days required for the first parasitoid emergence were recorded. The response of A. sp. near pseudococci females to different doses of LS (25–1350 μg) was also evaluated using sticky plate traps. The rate of mealybug parasitism by A. sp. near pseudococci was significantly increased by LS in the three parasitoid populations. PAc and LI had no significant effect on the wasp parasitism rate in most of the trials. However, the Italian population of the parasitoid responded to PAc, showing apparently a different behavioral pattern. The number of parasitoid females trapped did not significantly differ between tested doses of LS. The use of LS as an arrestant in host location by the A. sp. near pseudococci female is discussed.     

Host–plant relationships and natural enemies of the invasive mealybug,Rastrococcus iceryoides Green in Kenya and Tanzania

The invasive mango mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae), believed to be native to southern Asia has rapidly invaded Kenya and Tanzania. A survey was carried out from February 2008 to July 2009 to study its geographical distribution, host–plant relationships and associated parasitoids in both countries. Our results infer that R. iceryoides is widely distributed across the coastal belts of both countries. Rastrococcus iceryoides was recorded from 29 cultivated and wild host plants from 16 families. Twenty‐one of these host plants are new records. Among the cultivated host plants, M. indica (407.68 ± 9.26/twig and 75.68 ± 7.13/leaf in Kibaha, and 595.86 ± 17.2/fruit in Kinondoni) and Cajanus cajan (L.) Millspaugh (18.15 ± 4.22/leaf and 233.62 ± 18.9/twig in Morogoro) recorded the highest levels of infestation. Parkinsonia aculeata (394.62 ± 11.7/twig, 0.15 ± 0.03/leaf and 8.44 ± 0.94/fruit in Kinango), Caesalpinia sepiaria Roxb. (3.33 ± 0.76/leaf and 155.81 ± 9.16/twig in Kinondoni) and Deinbollia borbonica Scheff. (2.70 ± 0.66/leaf and 112.65 ± 5.3/twig in Kibaha) were found to be the most heavily infested wild host plants. Six parasitoid species were recovered and are reported here for the first time to parasitize R. iceryoides. Anagyrus pseudococci Girault was the most dominant species accounting for 21% parasitism on M. indica and 20% parasitism on P. aculeata in Tanzania and Kenya, respectively. Despite this, the ability of the parasitoid to regulate the population of R. iceryoides was inadequate. Therefore, there is a need for foreign exploration and introduction of efficient coevolved natural enemies from its aboriginal home of southern Asia to minimize its impact on horticulture in Africa.     

Degradation of chlorpyriphos and polyethylene by endosymbiotic bacteria from citrus mealybug

Chlorpyriphos is one of the major organophosphorus pesticides used widely to control a range of insect pests across several crops. This insecticide is hazardous to the environment and toxic to mammals, thus, it is essential to remove the same from the environment. Similarly, use of polythene is also increasing day by day. Therefore, it is highly important to identify ways to degrade chlorpyriphos and other pesticides from the environment. We studied the degradation of chlorpyriphos and polyethylene by Citrus mealybug (Planococcus citri) bacterial endosymbionts such as Bacillus licheniformis, Pseudomonas cereus, Pseudomonas putida and Bacillus subtilis. This investigation revealed that bacterial endosymbionts use the polythene as a source of carbon and solubilize them by their enzymatic machinery. The degradation of polyethylene by endosymbionts showed a significant reduction in weight of polyethylene sheet after 15, 30 and 45 days of treatment. The SEM images showed localized degradation of the polyethylene around the bacterial cells in the biofilm. Further, the tensile strength (percentage elongation) was significantly reduced after 45 days of incubation. The weight of paraffin wax showed significant reduction in B. cereus. A significant reduction in total amount of chlorpyriphos in soil was observed at an interval of 7, 14 and 21 days after treatment by the bacterial isolates. Among the bacteria, B. cereus and P. putida were found to be most effective. The results from this study show that endosymbionts can be significantly implicated in degrading chlorpyriphos and polyethylene from the environment.     

Acceptability and suitability of seven plant species for the mealybug Phenacoccus parvus

Survival, development and fecundity of cohorts of the mealybug Phenacoccus parvus Morrison were measured over one generation on seven plant species representing four plant families. Survival, development and fecundity were not significantly higher on the mealybug's principal field host, the weed Lantana camara L. (Verbenaceae), than on other plant species including Lycopersicon esculentum Miller (tomato) and Solanum melongena L. (eggplant). The acceptability of the leaves of the seven plant species to P. parvus first instar crawlers was measured on hatching, after active walking and after food deprivation. Lantana camara was the highest ranked plant species for all treatments. The number of crawlers settling on lower ranked plant species increased with the level of food deprivation.     

EPG waveform characteristics of solenopsis mealybug stylet penetration on cotton

The solenopsis mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), is a polyphagous insect known to cause severe damage to cotton (especially transgenic varieties) in South Asia, and currently poses a serious threat in Asia and potentially elsewhere. Stylet penetration behavior of P. solenopsis on cotton was monitored using the electrical penetration graph (EPG) technique (DC system) and the EPG characteristics were compared with those previously published from Phenacoccus manihoti Matile‐Ferrero and Planococcus citri (Risso). We identified and further characterized typical waveforms of A, B, C, and pd (together pathway), E1 and E2 (phloem), F (derailed stylet mechanics), and G (xylem). Five novel EPG aspects were distinguished in the EPG waveforms from P. solenopsis: (1) obvious B waveforms occurred following waveform A, (2) during waveform C, some aphid‐like E1e waveforms were observed, (3) prolonged potential drops (pd) up to >1 h occurred with two continuously alternating sub‐phases pd1 and pd2, (4) the pd1 waveform always occurred as the first waveform related to phloem sieve elements, preceding the other phloem waveforms (E), the labeling of which we changed to achieve a better comparison to the aphid E waveforms, and (5) waveform F, related to derailed stylet mechanics occurred but was not reported from other mealybugs so far. This is mainly a waveform morphology study to extend existing knowledge on mealybug EPGs to investigate mealybug‐host plant interactions. Further experimental verification of waveform correlations with plant tissue positions of stylet tips and insect activities is still needed.