Variety Of Host Plants Research Articles

Characterization and potential mechanisms of resistance of cucumber genotypes to Bemisia tabaci (Hemiptera: Aleyrodidae)

Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) is a major pest of several agricultural crops, being vector of an extreme number of viruses. The broad variety of host plants, high adaptability and evolution of resistance to insecticides evidence the difficult in the management of B. tabaci in the agriculture system. Host plant resistance is a valuable and sustainable method of insect management. To date, few studies have characterized the resistance of cucumber (Cucumis sativus L.) genotypes to B. tabaci, although this plant is one of the most preferred host of this hemipteran. The objective of this study was to assess the resistance of 60 cucumber genotypes against B. tabaci in greenhouse and laboratory conditions and to characterize the mechanisms of resistance involved based on morphological and physical plant parameters. Initially, 12 genotypes were selected in a screening bioassay. In general, ‘IAC-1214’ expressed high levels of antixenosis to the insect, causing low attractiveness to adults and non-preference for oviposition and colonization. 'Wellington' prolonged the development of the insect and provoked low levels of adult emergence, expressing levels of antibiosis. Antibiosis and/or antixenosis were detected in ‘IAC-1201’, ‘Campeiro’, ‘Japones’, and ‘IAC-1311’, while antixenosis was detected in ‘Kyria’ and ‘IAC-1175’. The density of the trichomes and the color of the leaves are described and discussed here. The selected genotypes present potential application in integrated programs that focus on reducing populations of B. tabaci in the agricultural system and in breeding programs aiming to explore resistant genotypes against the insect.

Interactions between Magnaporthiopsis maydis and Macrophomina phaseolina, the Causes of Wilt Diseases in Maize and Cotton.

Fungal pathogens are a significant threat to crops worldwide. The soil fungus, Magnaporthiopsis maydis, severely affects sensitive maize hybrids by causing the rapid wilting of plants at the maturity stage. Similarly, the soil fungus, Macrophomina phaseolina, develops in a variety of host plants, which leads to rot and plant mortality. The presence of both pathogens together in diseased cotton plants in Israel suggests possible interactions between them. Here, these relationships were tested in a series of experiments accompanied by real-time PCR tracking in maize and cotton. Despite the fact that neither of the pathogens was superior in a growth plate confrontation assay, their co-inoculum had a significant influence under field conditions. In maize sprouts and fully matured plants, infection by both pathogens (compared to inoculation with each of them alone) led to lesser amounts of M. maydis DNA but to increased amounts of M. phaseolina DNA levels. These results were obtained under a restricted water regime, while optimal water irrigation led to less pronounced differences. In water-stressed cotton sprouts, infection with both pathogens led to an increase in DNA amounts of each of the pathogens. Whereas the M. maydis DNA levels in the double infection remain high at the end of the season, a reduction in the amount of M. phaseolina DNA was observed. The double infection caused an increase in growth parameters in maize and cotton and decreased levels of dehydration in maize plants accompanied by an increase in yield production. Dehydration symptoms were minor in cotton under an optimal water supply. However, under a restricted water regime, the double infection abolished the harmful effect of M. phaseolina on the plants’ development and yield. These findings are the first report of interactions between these two pathogens in maize and cotton, and they encourage expanding the study to additional plant hosts and examining the potential involvement of other pathogens.

Conserve the eco-evolutionary dynamic, not the subspecies: phenological divergence and gene flow between temporal cohorts of Euphilotes ancilla endemic to southern Nevada

Euphilotes ancilla purpura and cryptica (Lycaenidae), butterflies endemic to the Spring Mountains (Clark Co., Nevada), have been described as two univoltine, temporally isolated, sympatric taxa that utilize different early- and late-flowering larval host plant varieties (Eriogonum umbellatum). However, our results from field and laboratory indicate that this is not the case. The subspecies overlap in timing of adult reproductive flight (compilation of field records 1977 to 2018) and laboratory emergence of adults from early-season, non-diapause pupae indicate butterflies are not univoltine. Genetic samples collected from putative E. a. purpura (Early cohort) and cryptica (Late cohort) subpopulations show no evidence of genetic structure indicative of allochronic isolation in phylogenies of 26 mitochondrial DNA COI haplotypes and 18 nuclear ITS1 alleles. Analysis of molecular variance revealed 89% of mitochondrial DNA variation structured within and among subpopulations, with only 11% between the purportedly isolated subspecies. Analysis of isolation and migration indicated gene flow from the Early to Late cohort was 3 × greater than in the opposite direction. We conclude that, rather than two separate subspecies, Euphilotes ancilla exists in a network of partially interconnected subpopulations extending from 1750 to 3000 m across much of the Spring Mountains. Gene flow is related to the timing of adult flight and host plant flowering, contributing to the genetic variation in phenology necessary for evolutionary tracking of shifting flowering periods of larval host plants. Maintenance of connectivity and gene flow across the Spring Mountains is therefore essential for population persistence of both cohorts in the face of environmental change.

Phylogenetic Characterization of Botryosphaeria Strains Associated with Asphondylia Galls on Species of Lamiaceae

In the last decade, Botryosphaeria dothidea has been steadily reported as an associate of gall midges (Diptera, Cecidomyiidae) in a variety of host plants and ecological settings. This cosmopolitan fungus is well-known for its ability to colonize many plant species, as both a pathogen and an endophyte. Thus, the shift from this general habit to a lifestyle involving a strict symbiotic relationship with an insect introduces expectancy for possible strain specialization which could reflect separated phylogenetic lineages. Considering the recent taxonomic revision concerning species of Botryosphaeria, we evaluated the phylogenetic relationships among strains recovered from Asphondylia galls collected on several species of Lamiaceae in Poland and in Italy, and all the currently accepted species in this genus. A number of strains previously characterized from gall samples from Australia and South Africa, whose genetic marker sequences are deposited in GenBank, were also included in the analysis. As a result, full identity as B. dothidea is confirmed for our isolates, while strains from the southern hemisphere grouped separately, indicating the existence of genetic variation related to the geographic origin in the association with gall midges.

A new stunt nematode, Geocenamus chengi n. sp. (Nematoda: Merliniinae) in the rhizosphere of tea (Camellia sinensis) from Zhejiang Province, China.

The tea plant is native to China; the country has the greatest tea production areas in the world. In an attempt to investigate the nematode biodiversity associated with the tea plantations of Hangzhou, Zhejiang Province, a population of stunt nematode was detected. This group of nematodes is comprised of migratory ecto-parasites of roots and can subsist on a variety of host plants. Therefore, the detected population was studied carefully using the integrative taxonomy approach and identified as a new species of genus Geocenamus. Geocenamus chengi n. sp. can be characterized by females having six incisures in the lateral field; labial region is dome shaped and slightly offset from the rest of the body having four to five annuli; head framework is weakly developed; deirids are absent; excretory pore is located at the anterior region of basal pharyngeal bulb. Under SEM, the vulva is a transverse slit, vulval lips are elongated and ellipsoidal with epiptygma. The tail is annulated, elongated, and conical having bluntly pointed tip and a terminal hyaline region that forms 21 to 33% of the tail length. Spicule is 22 to 25 μm long, gubernaculum is saucer shaped; bursa is crenated covering the tail until the hyaline tail region. Morphologically, the species is close to G. circellus, G. joctus, G. loofi, G. ordinarius, G. processus, G. tetyllus, and G. tortilis. Phylogenetic relationships of the new species based on D2-D3 expansion domains of 28 S, ITS, and 18 S rRNA genes indicated that G. chengi n. sp. clustered in a separate clade with G. vietnamensis.

Impact of season on leaf beetles diversity in garbhanga reserve forest (coleoptera, chrysomelidae) and its feeding pattern

The paper aims to study the impact of season on the diversity of leaf beetle population in Garbhanga Reserve Forest and how it inflicts damage to the vegetation through its different feeding habits in a wide variety of host plants. A total of 1673 individuals belonging to 24 species under 14 genera and 5 subfamilies were recorded from the five chosen plots. The diversity of Chrysomelids beetle in the five chosen plot were compared by using different parameters- species composition, total abundance, species richness and diversity.

Genome-wide markers reveal temporal instability of local population genetic structure in the cotton fleahopper, Pseudatomoscelis seriatus (Hemiptera: Miridae).

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae), is a pest of upland cotton, Gossypium hirsutum L. (Malvales: Malvaceae), that attacks pre-floral buds (squares), leading to abscission and yield losses. In the Brazos Valley cotton production area of Texas (USA), P. seriatus exhibits a seasonal pattern of host use. In spring, eggs hatch from stems of the overwintering host, woolly croton, Croton capitatus Michx. (Malpighiales: Euphorbiaceae). During the growing season, individuals feed on a variety of host plants, including cotton. Adults return to woolly croton at season end to oviposit. We investigated if genetic differentiation exists between populations infesting cotton and those infesting alternative hosts, and whether woolly croton serves as a year-end site of admixture that could be suitable as a natural refuge for the purposes of insect resistance management. We combined high-throughput DNA sequencing with fine-scale spatio-temporal sampling to test (i) whether a population genomic approach would recover patterns of genetic variation consistent with earlier studies and (ii) if local genetic population structure was robust to seasonal changes in local habitat over time. We found high gene flow among populations of P. seriatus collected from different host plants in the Brazos Valley. We also identified temporal instability of the local population genetic structure, including the near complete loss of a genotypic group that had been previously abundant. We support the status of woolly croton as a natural refuge that promotes year-end gene flow between genotypes infesting cotton and those infesting alternative hosts. © 2019 Society of Chemical Industry.

Physical and chemical traits affecting the oviposition preference of honeysuckle geometrid, Heterolocha jinyinhuaphaga Chu among honeysuckle varieties

Oviposition preference is an important aspect of insect reproduction, females are able to evaluate the nutritional and structural properties of a plant and normally oviposit on the plant with suitable characteristics, thereby allowing their offspring to feed on a high-quality food source to enhance the offspring’s survival rate. Understanding of the host plant oviposition preferences of phytophagous insects may help to develop insect-resistant cultivars for use in integrated pest management. In this study, we investigated the physical and chemical traits that affect the oviposition preference of Heterolocha jinyinhuaphaga Chu among different honeysuckle varieties (wild variety, Jiufeng 1, Xiangshui 1, and Xiangshui 2) under laboratory conditions. The oviposition preference of H. jinyinhuaphaga differed among the four host plant varieties, with both oviposition quantity and oviposition percentage orders being wild variety > Jiufeng 1 > Xiangshui 2 > Xiangshui 1. Taxis response test using the Y-tube olfactometer obtained similar results, showing the response percentages of 91.67%, 87.47%, 81.78%, and 78.36% for the wild variety, Jiufeng 1, Xiangshui 2, and Xiangshui 1, respectively, compared with the air control. Correlation analysis indicated that both oviposition quantity and oviposition percentage by H. jinyinhuaphaga on the four host varieties were positively correlated with the soluble sugar content, protein content, total flavonoid content, and chlorogenic acid content of leaves, but negatively correlated with the hair density, hair length, water content, and fat content of leaves. Further path analysis indicated that protein content had the main effect on the oviposition quantity by H. jinyinhuaphaga. These results provide an important basis for breeding and developing insect-resistant honeysuckle varieties.

Bioecology of Anastrepha alveata Stone (Diptera: Tephritidae) associated with wild plum fruits Ximenia americana L. (Olacaceae)

Fruit flies (Diptera: Tephritidae) are considered important pests of fruticulture due to considerable losses to production and limitation to free transit of fresh fruits. A generalist species is cresature that can live or feed on a wide variety of environemnts or host plants. Although, Anastrepha is a generalist species but infests a small range of plants. The specificity of this species with host plants is a peculiar characteristic of genus Anastrepha. Therefore, it is important to understand the host species and its feeding behaviour on host plants. This way, we will better know its ecology, biology and evolution for rational control ways and measures. Therefore, this study aimed at understanding the biology of Anastrepha alveata Stone (Diptera: Tephritidae). A study was carried out under controlled laboratory conditions (27 ± 2°C temperature, 70 ± 5% RH, photoperiod 12 hours) during the period from November/2015 to October/2017. Anastrepha alveata adults were obtained from wild plum fruits Ximenia americana L. (Olacaceae), collected from Savanna area in two fructification periods. One-hundred and fifty Anastrepha alveata adults were collected (60 females and 90 males) to determine sexual maturity, mating behavior, fecundity and longevity. The sexual maturity for Anastrepha alveata was 8-13 days after emergence for females. At this age they emitted signal of acceptance for mating and copulation. For males, 5-7 days after emergence this mating signals was given, which was characterized by the protrusion of the lateral abdominal pleural glands. The mating rhythm of Anastrepha alveata was crepuscular/nocturnal, beginning around 6 p.m. and extending to/after 9 p.m. Anastrepha alveata females did not mate with more than one male but mated more than once. The number of males did not affect significantly the mating time, the number of eggs and the longevity of Anastrepha alveata. The mean pupal period for Anastrepha alveata was 17.5 days. Two preferential peaks for adult emergence were observed at 10:00 am and 03:00 pm. The longevity of the adult insects was greater than 300 days, surviving until the fructification of its host (wild plum) in the following year. Therefore, A. alveata has a strictly monophagous food habit associated with the Ximenia americana host.

Keanekaragaman kumbang sungut panjang (Coleoptera: Cerambycidae) di Hutan Lindung Wehea, Kalimantan Timur

Kumbang sungut panjang (longhorn beetle) (Coleoptera: Cerambycidae) adalah kelompok serangga yang terdiri atas banyak spesies dan bernilai penting secara ekonomi, berasosiasi dengan beragam spesies tumbuhan inang dan merupakan famili kumbang yang paling terkenal. Kehadiran famili ini di Hutan Lindung Wehea (HLW), Kecamatan Muara Wahau, Kabupaten Kutai Timur, Provinsi Kalimantan Timur belum pernah dilaporkan sehingga tulisan ini adalah informasi pertama mengenai keanekaragaman spesies kumbang sungut panjang di HLW. Tujuan dari penelitian ini adalah untuk mengetahui keanekaragaman spesies, spesies yang dominan, subdominan dan kemerataan penyebaran individu kumbang sungut panjang Famili Cerambycidae di HLW. Kumbang ditangkap dengan menggunakan perangkap malaise dan perangkap dari daun nangka (Artocarpus heterophyllus) di dalam plot penelitian berukuran 20 m x 100 m (0,2 ha). Hasil penelitian ini menunjukkan bahwa indeks keanekaragaman Simpson adalah sebesar 0,93 (keanekaragaman tinggi). Di antara 42 spesies yang ditemukan, 6 spesies termasuk dominan, 8 spesies subdominan, dan 28 spesies tidak dominan. Spesies yang dominan adalah Epepeotes spinosus (Thomson), E. luscus (Fabricius), Acalolepta rusticatrix (Fabricius), Ropica quadricristata (Breuning), Pterolophia melanura Pascoe, dan Egesina (Callienispia) minuta (Fisher). Indeks kemerataan Simpson (E) adalah sebesar 0,36 (penyebaran individu masing-masing spesies tidak merata).

Identification of a cytochrome P450 CYP6AB60 gene associated with tolerance to multi-plant allelochemicals from a polyphagous caterpillar tobacco cutworm (Spodoptera litura)

Generalist phytophagous insects adapt to adventurous chemical environment in a wide variety of host plants by extraordinary detoxifying metabolic abilities. However, how polyphagous insect cope with the diversity of plant defenses remains largely unknown and only a few counter-defense genes detoxifying a wide range of toxic secondary metabolites have been well characterized. Here, we identify a cytochrome P450 gene (CYP6AB60) from tobacco cutworm (Spodoptera litura) in response to three different plant's defense metabolites. After being exposed to artificial diet supplemented with coumarin (COU), xanthotoxin (XAN) or tomatine (TOM), activities of P450 and CYP6AB60 transcript levels in both midgut and fat body tissues were significantly increased. Developmental expression analysis revealed that CYP6AB60 was expressed highly during the larval stages, and tissue distribution analysis showed that CYP6AB60 was expressed extremely high in the midgut, which correspond to the physiological role of CYP6AB60 from S. litura larvae in response to plant allelochemicals. Furthermore, when larvae are injected with double-stranded RNA (dsRNA) specific to CYP6AB60, levels of this transcript in the midgut and fatbody decrease and the negative effect of plant's defense metabolites on larval growth is magnified. These data demonstrate that the generalist insect S. litura might take advantage of an individual detoxificative gene CYP6AB60 to toxic secondary metabolites from different host plants. The CYP6AB60 can be a potential gene to carry out RNAi-mediated crop protection against the major polyphagous pest S. litura in the future.

Differences in infectivity and pathogenicity of two Plantago asiatica mosaic virus isolates in lilies

Plantago asiatica mosaic virus (PlAMV) is a member of the genus Potexvirus in the family Alphaflexiviridae and has been isolated from a variety of host plants. In particular, PlAMV isolates from ornamental lilies (Lilium spp.) cause necrotic symptoms in these plants, which significantly reduces their commercial value. However, it has not been clear whether PlAMV isolates from other host plants differ in their infectivity and/or pathogenicity to ornamental lilies, and whether growth conditions affect infectivity and pathogenicity. In this study, we inoculated an edible lily species (Lilium leichtlinii) and seven varieties of ornamental lilies with two PlAMV isolates, an isolate from ornamental lily (PlAMV-OL) and an isolate from edible lily (PlAMV-Li1). We found that PlAMV-OL showed higher infection rates and exhibited necrotic symptoms more frequently in lilies than PlAMV-Li1. Moreover, we observed higher infection rates of PlAMV-OL in open field than in greenhouse, and higher rates of necrotic symptoms in autumn test than in spring test, suggesting that growth conditions and season affect infectivity and pathogenicity of PlAMV in lilies. Our study would provide important information for estimating the risk of necrotic disease caused by PlAMV, as well as for cultivation management preventing the occurrence of the disease.

Asymptomatic Host Plant Infection by the Widespread Pathogen Botrytis cinerea Alters the Life Histories, Behaviors, and Interactions of an Aphid and Its Natural Enemies.

Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and structure of insect communities. Changes in host plants may have direct effects on the life-histories of their insect herbivores, which can then influence their value as prey to their natural enemies. While there have been many studies that have explored the effects of infection when plants show symptoms of disease, little is understood about how unexpressed infection may affect interactions at higher trophic levels. We examined how systemic, asymptomatic, and seed-borne infection by the ubiquitous plant pathogen Botrytis cinerea, infecting two varieties of the lettuce Lactuca sativa, affected aphids (the green peach aphid, Myzus persicae) and two widely used biocontrol agents (the parasitoid Aphidius colemani and the ladybird predator Adalia bipunctata). Lettuce varieties differed in host plant quality. Asymptomatic infection reduced chlorophyll content and dry weight of host plants, irrespective of plant variety. Aphids reared on asymptomatic plants were smaller, had reduced off-plant survival time and were less fecund than aphids reared on uninfected plants. Parasitoids showed reduced attack rates on asymptomatically infected plants, and wasps emerging from hosts reared on such plants were smaller and showed reduced starvation resistance. When given a choice in an olfactometer, aphids preferentially chose uninfected plants of one variety (Tom Thumb) but showed no preference with the second (Little Gem) variety. Parasitoids preferentially chose aphids on uninfected plants, irrespective of host plant variety, but ladybirds did not show any such preference. These results suggest that the reduced quality of plants asymptomatically infected by Botrytis cinerea negatively affects the life history of aphids and their parasitoids, and alters the behaviors of aphids and parasitoids, but not of ladybirds. Fungal pathogens are ubiquitous in nature, and this work shows that even when host plants are yet to show symptoms, pathogens can affect interactions between insect herbivores and their natural enemies. This is likely to have important implications for the success of biological control programs.

Effect of Temperature and Aphid-Host Plant Variety on Performance and Thermal Requirments of Coccinella undecimpunctata L. and Cheilomenes propinqua isis (mulsant)

In this study, the single and common effects of temperature (20, 25 and 30 ± 1˚C) and eggplant varieties (Classic, 0111, and Anan) on the developmental performance and heat requirements of Coccinella undecimpunctata L. and Cheilomenes propinqua isis (Mulsant) were examined. The predators were fed upon Aphis gossypii Glover that reared on the three eggplant Solanum melongena (L.) varieties. The two-way ANOVA showed that there was significant effects of temperature and host plant varieties on the total developmental times of both predators. However, the interaction between temperature and host plant variety interaction had only significant effect on the total developmental times of C. undecimpunctata. The results also revealed that the developmental times (DT) of both predators were decreased with increasing the temperature, whereas the developmental rates increased. Based on lower developmental threshold (T0) values, the more tolerant stage for coldness was the pupal stage of both C. undecimpunctata and C. propinqua isis on the three eggplant varieties. On the contrary, the more sensitive stage for low temperature degrees differed for both species: the eggs stage for C. undecimpunctata and the larval stage for C. propinqua isis. The minimum (T0) values for the entire development of both predators were recorded on Classic variety. The heat units (degree-days, DD’s) estimated for each stage showed that aphids produced on Classic variety lowered the amount of heat required by both predator species to complete their development. Further, the larval stage of both predatory species required more heat units to develop at each aphid-host plant variety combination than other stages. These results suggest that eggplant var. Classic has to be considered, in mass rearing programs, to produce a high nutritional prey for both predator species. This might maximize the population of these predators. As well, 30 °C would multiply the population of both predators under the same rearing conditions, and thus has to be generalized.

Management of <i>Helicoverpa armigera</i> (Lepidoptera: Noctuidae) by Nutritional Indices and Botanical Extracts of <i>Millettia ferruginea</i> and <i>Azadirachta indica</i>

The development of hosts that are resistant and evaluation of botanical extracts to H. armigera Hubner (Lepidoptera: Noctuidae) is crucial for sustainable management, yet very limited in Ethiopia. Therefore, this study was done to identify alternative methods to insecticide control through host consumption study and botanical extracts. The performance of third-fifth larval stages of H. armigera on three host plant varieties including chickpea, tomato and faba bean and botanical extracts against the third larval instars and oviposition deterrence was studied under laboratory condition (22°C ± 2°C, 55% ± 5% RH, 12:12 L: D photoperiod). Significant differences were found in the efficiency of conversion of ingested food (ECI%) (F = 80.06; df = 6, 2; p < 0.05) and efficiency of conversion of digested food (ECD%) (F = 175.91; df = 6, 2; p < 0.05) values of H. armigera reared on the three host plant varieties of the whole larval instars. The minimum relative consumption rate (RCR) (11.271 ± 0.328) and maximum approximate digestibility (AD) (177.9 ± 1.928) values of the whole larval instars were on Dagaga and Koshari, respectively. The values of relative growth rate (RGR), ECI% and ECD% of the whole larval instars were highest on chickpea varieties and lowest on tomato Koshari. Among chickpea varieties, Habru was relatively resistant to larval instars of H. armigera. Botanical extracts at 50% neem oil (NO), 5% birbira seed extract (BSE) and 5% neem seed extract (NSE) (18.4%) resulted superior in larval mortality however, statistically not different. At both 5% and 2.5% concentration level of botanical extracts the minimum larval mortality was recorded from neem leaf extract (NLE). Maximum numbers of eggs were laid on control treatments and the minimum eggs were on 5% BSE. The deterrent effect of 50% neem oil was stronger (ODI = 17.66%) than that of 5% BSE (ODI = 14%) which is statistically similar value with 5% NSE (ODI = 13%). In conclusion, the result indicated that use of Habru chickpea variety with 50% NO was very effective in controlling both the larvae and deterring the adults of H. armigera from egg lying. These measures could be important in the wider managements of H. armigera by integrating host resistance and botanical extracts.

Secondary Metabolite Profiling of Four Host Plants Leaves of Wild Silk Moth Attacus atlas L.

Secondary metabolites may affect insect herbivores’ host plant preferences. Attacus atlas L. larvae are known have a wider variety of host plants compared with other members of the Attacus genus. This research compared the metabolic profiles of four A. atlas host plants: keben (Barringtonia asiatica (L.) Kurz), dadap (Erythrina lithosperma Miq.), gempol (Nauclea orientalis L.), and soursop (Annona muricata L.). Leaves were collected from Sawit Sari Research Station, Yogyakarta. Terpenoid was extracted by macerating the leaves in ethyl acetate and subjecting them to GC-MS analysis, while alkaloid, tannin, and flavonoid were extracted through percolation. Total alkaloids, tannins, and flavonoids were measured using spectrophotometric analysis. Multivariate data analysis using PAST ver. 3.0 was performed on the GC-MS data. Based on the PCA scatter plot of the GC-MS data, keben leaves were clustered separately from the other three leaves by PC1. Dadap and gempol leaves were clustered together due to the phytol content while caryophyllene was detected only in soursop leaves. Neophytadiene was detected in all of the leaves, suggesting that this terpenoid may serve as a signal to locate the host plants. Keben leaves contained the lowest alkaloids and highest tannins and flavonoids compared with the other leaves. These secondary metabolites may determine the host plant suitability for culturing the A. atlas.

Two genomes of highly polyphagous lepidopteran pests (Spodoptera frugiperda, Noctuidae) with different host-plant ranges

Emergence of polyphagous herbivorous insects entails significant adaptation to recognize, detoxify and digest a variety of host-plants. Despite of its biological and practical importance - since insects eat 20% of crops - no exhaustive analysis of gene repertoires required for adaptations in generalist insect herbivores has previously been performed. The noctuid moth Spodoptera frugiperda ranks as one of the world’s worst agricultural pests. This insect is polyphagous while the majority of other lepidopteran herbivores are specialist. It consists of two morphologically indistinguishable strains (“C” and “R”) that have different host plant ranges. To describe the evolutionary mechanisms that both enable the emergence of polyphagous herbivory and lead to the shift in the host preference, we analyzed whole genome sequences from laboratory and natural populations of both strains. We observed huge expansions of genes associated with chemosensation and detoxification compared with specialist Lepidoptera. These expansions are largely due to tandem duplication, a possible adaptation mechanism enabling polyphagy. Individuals from natural C and R populations show significant genomic differentiation. We found signatures of positive selection in genes involved in chemoreception, detoxification and digestion, and copy number variation in the two latter gene families, suggesting an adaptive role for structural variation.

Diversity of the Most Commonly Reported Facultative Symbionts in Two Closely-Related Aphids with Different Host Ranges.

Richness and abundance of facultative symbionts vary strongly with aphid species and genotype, symbiont strain, host plant, biogeography, and a number of abiotic factors. Despite indications that aphids in the same ecological niche show similar levels of facultative symbiont richness, existing reports do not consider the potential role of host plants on aphid microbial community. Little is known about how oligophagy and polyphagy may be influenced by secondary symbiont distribution, mainly because studies on secondary symbiont diversity are biased towards polyphagous aphids from the Northern Hemisphere. Here, we demonstrate the richness and abundance of the most common aphid-associated facultative symbionts in two tropical aphid species, the oligophagous Aphis (Toxoptera) citricidus (Kirkaldy) (Hemiptera: Aphididae) and the polyphagous Aphis aurantii (Boyer de Fonscolombe) (Hemiptera: Aphididae). Aphis citricidus is restricted to Citrus sp. host plants and closely related genera, whereas A. aurantii successfully exploits a wide variety of host plants from different families. Both were collected in the same ecological niche and our data basically indicated the same richness of secondary symbionts, but the abundance at which secondary symbionts occurred was very distinct between the two species. Spiroplasma was the most abundant facultative symbiont associated with A. citricidus and A. aurantii in the ecological niche studied. Single and multiple secondary symbiont infections were observed, but diversity of multiple infections was particularly high in A. citricidus. We discuss our findings and suggest hypotheses to explain causes and consequences of the differences in secondary symbiont diversity observed between these two aphid species.

Life-table study of mango leaf cutting weevil, Deporaus marginatus Pascoe (Coleoptera: Curculionidae) feeding on four mango cultivars

Mango leaf cutting weevil, Deporaus marginatus Pascoe (Coleoptera: Curculionidae) is a devastating pest of freshly emerged mango foliage. The immature development, survivorship and adult reproduction of the weevil were investigated on four popular mango cultivars (Langra, Amrapali, Fazli and Ashwina) under the laboratory conditions and life-table parameters were estimated. The immature developmental periods ranged from 17.3 to 19.8days with female ratio of 5.5–6.2. Ault longevity ranged 43.6days for female and 66.2days for males. Effects of the host plant varieties were not significant on the immature development or sex ratio, but significantly influenced the adult performances; longevity, reproduction and also life table parameters. Among the mango varieties tested, Ashwina variety could be the most preferable with higher population growth rate while the Langra and Fazli were the lesser suitable with longer doubling time or lower reproduction. Further study could pursue the nutritional and antibiotic mechanisms which could be responsible for the different performance of the herbivore insect on the mango plants.

Host-plant variety and not climate determines the establishment and performance of Aceria lantanae (Eriophyidae), a biological control agent of Lantana camara in South Africa.

The flower-galling mite Aceria lantanae (Cook) (Trombidiformes: Eriophyidae) was released for the biological control of Lantana camara L. (Verbenaceae) in South Africa in 2007, but has displayed variable and patchy establishment throughout the weed's range. Surveys were undertaken in 2013-2014, both seasonally and during the mite's peak infestation periods, to determine the influence of climatic factors on its performance. Although there were seasonal differences in the percentages of mite-infested inflorescences, these did not differ significantly between altitudinal zones. There were also no significant relationships between the percentages of mite-infested inflorescences and either of annual rainfall, temperature or relative humidity. A field inoculation trial revealed significant differences between 10 common South African L. camara varieties in their susceptibility to A. lantanae. Only three varieties displayed appreciable susceptibility (50-61% of inflorescences infested), whereas six displayed only slight to moderate susceptibility (8-21%) and one displayed a lack of susceptibility (no infestation). These data support the contention that differential varietal susceptibility and not climate is responsible for the variable performance of A. lantanae on L. camara in South Africa. Complementing the current biotype of A. lantanae, originally sourced from Florida (USA), with other biotypes from different L. camara genotypes in Central and South America could increase the mite's impact on the weed.