Bitter Cherry Research Articles

Fruit Quality and Production Parameters of Some Bitter Cherry Cultivars

Bitter cherries (Prunus avium var. sylvestris Ser.) represent a valuable raw material in the traditional Eastern European food industry with high potential within the horticultural chain and circular economy in the context of global food security due to exceptional nutritional properties. The present study was carried out in the period 2022–2024 and had as its main purpose the evaluation of the fruit quality and production indices of some bitter cherry cultivars suitable for the technological norms specific to industrial processing. Five bitter cherry cultivars (C1-Amaris, C2-Amar Maxut, C3-Amar Galata, C4-Silva, C5-Amara) were studied and analyzed in terms of fruit quality—morpho-physiological and organoleptic traits, and physical and chemical parameters—and general productivity—tree vigor, fruiting, and yield indices. The results highlighted a wide variability in the physical characteristics of bitter cherries, with an average weight between 3.3 and 4.9 g and the color of the skin varying from yellow with redness to dark red and blackish. Regarding the chemical attributes, antioxidant activity was relatively higher in fruits with a more intense bitter taste (89.3 μg Trolox·g−1 f.w for C2 and 89.1 μg Trolox·g−1 f.w. for C4 and C5), a fact also found in the content total of polyphenols (with a maximum value of 743.2 mg GAE·100 g−1 f.w at C2). Total soluble solids content had an average value of 20.51°Brix and titratable acidity of 0.85 g malic acid·100 g−1 f.w. The influence of local environmental factors on the productivity of bitter cherry cultivars was highlighted by significant statistical differences (p < 0.05) between cultivars. Thus, the resistance to frost in the full flowering phenophase had an average value of 86.69%, and regarding the resistance to fruit cracking, the highest percentage was found in C1, with 99.79% unaffected fruits. The productivity index per tree had an average value of 0.24 kg per cm2 trunk cross-section area. The physico-chemical properties of the fruits and the productivity of bitter cherry cultivars support the possibility of their efficient use in processing and the food industry, yielding high-quality products with nutraceutical value.

Composition characteristics of alcoholic extracts from black currant (Ribes nigrum), sour cherry (Prunus cerasus) and bitter cherry (Prunus avium)

The paper elucidates the potential of biologically active substances of sour cherry, blackcurrant, and bitter cherry fruits through the prism of fundamental research and quantifications achieved through analytical methods of study. The hydro-alcoholic extracts from blackcurrant and sour cherry presented values of over 90% DPPH• radical inhibition, being also the most stable by composition during storage of 30 and 90 days. Based on the HPLC representatives, it was established that the main anthocyanin components in sour cherry extracts are: cyanidin-3-O-glucosyl-rutinoside, (2.4 mg/100 g), cyanidin-3-O-rutinoside, (162 mg/100 g) and cyanidin-3-O-monoglucosil-rutinoside (3.86 mg/100 g). These anthocyanin compounds represent over 62.8% of the 7 anthocyanins identified in blackcurrant extract. A major positive correlation, R2 = 0.98 and p < 0.01, between antioxidant capacity, anthocyanin content, and color parameters, was established confirming that these phenolic compounds are the most important color constituents in the analyzed fruits. Thus, fresh or frozen cherry and blackcurrant fruits are an excellent source of phenolic substances, rich in vitamins and resistant to oxidation.

Diapause of the Western cherry fruit fly, Rhagoletis indifferens (Diptera: Tephritidae): metabolic rate and overwintering adaptations.

The Western cherry fruit fly, Rhagoletis indifferens (Curran), is a Tephritid fly in the Pacific Northwest and is known to infest native bitter cherry, Prunus emarginata (Douglas ex Hooker), which is distributed throughout the Cascade Mountain range. This species occupies temperate to alpine climates and exhibits overwintering adaptations of diapause and supercooling. Isothermal and differential scanning calorimetry were used to determine the effects of diapause chilling duration and post-chilling warm rearing on the metabolic rate and supercooling point of R. indifferens. Previous studies have included the effects of chilling duration on post-diapause development and emergence as well as on the levels of metabolic reserves. Metabolic rate of R. indifferens, was used to calculate the ability of this species to remain in diapause for more than 1 yr as well as predicting the potential effects of climate change on the future abundance and distribution. It was determined that R. indifferens could diapause for more than 1 yr based on the levels of metabolic reserves and metabolic rate.

Host plant and immature stages of Setabara histrionica (MacGillivray) (Hymenoptera, Tenthredinidae)

The North American sawfly Setabara histrionica (Tenthredinidae: Heterarthrinae) is previously known only from adult collections but has been hypothesized to feed upon trees in the genus Prunus. We discovered a population of leaf-mining sawflies in Washington on Prunus emarginata and identified it as S. histrionica using combined morphological and molecular analysis. We observed preference in oviposition site selection on the host plant, with most eggs deposited on the margin of the basal third of the leaf, and on leaves growing within 1 meter of the ground. We include a description of the egg, larval stages, mine and phenology of S. histrionica, and an update to Smith’s (1971) key to Heterarthrinae larvae.

RESULTS OBTAINED FROM SWEET CHERRY BREEDING IN IAŞI, ROMANIA

From 1994 - 2016, the Research Station for Fruit Growing (RSFG) Iași approved 28 cherry cultivars, of which three were early cultivars (Cetăţuia, Cătălina and Amaris), 20 were middle maturation cultivars (Maria, Golia, Ştefan, Bucium, Iaşirom, Tereza, Lucia, Radu, Oana, Alexus, Andreiaş, Ludovan, Cociuvaş, Iosifan, Paulică, Mihailis, Muşatini, Elaiaşi, Amar Maxut, and Amar Galata), and five had late maturation (Andante, Marina, Croma, Margonia, and George). Van, as the most widespread cultivar in Romanian orchards, was used as a control. The sweet cherry cultivars were created through direct hybridisation or free pollination. Maria Cultivar is the first Romanian self-fertile cultivar. The locally approved bitter cherry biotypes are Amar Maxut with black fruit, Amar Galata with double-coloured fruit, and Amaris with dark red fruit. Regarding the tree’s vigour, cultivars Amaris, Tereza, Ştefan, and Golia recorded weak vigour, in comparison with the other cultivars, which had medium vigour. Bitter-tasting cherry cultivars have semi-firm pulp with semi-adherence to the stone, and the fruit weight was under 7 g. All 28 cultivars presented high precocity, productivity, fruit quality, and resistance to frost, drought, and diseases.

Contrast in Post-Chill Eclosion Time Strategies Between Two Specialist Braconid Wasps (Hymenoptera: Braconidae) Attacking Rhagoletis Flies (Diptera: Tephritidae) in Western North America.

Parasitoids comprise a speciose insect group, displaying a wide array of life history strategies. In the Pacific Northwest of the United States, the tephritid fruit flies Rhagoletis tabellaria (Fitch) and Rhagoletis indifferens Curran infest red osier dogwood, Cornus sericea L. (Cornaceae), and bitter cherry, Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae), respectively. The flies are parasitized by different braconid wasps at different life stages; Utetes tabellariae (Fischer) oviposits into R. tabellaria eggs, whereas Diachasma muliebre (Muesebeck) oviposits into R. indifferens larvae feeding in cherries. Because Rhagoletis only have one major generation a year and the wasps attack temporally distinct fly life stages, we predicted that eclosion times of U. tabellariae should more closely follow that of its host than the larval-attacking D. muliebre. As predicted, U. tabellariae eclosed on average 6.0-12.5 d later than R. tabellaria, whereas D. muliebre eclosed on average 32.1 d after R. indifferens. Unexpectedly, however, longer chill duration differentially affected the systems; longer overwinters minimally influenced eclosion times of R. tabellaria and U. tabellariae but caused earlier eclosion of both R. indifferens and D. muliebre. Results imply that in temperate regions, diapause timing in braconid wasps evolves in response to both host life stage attacked and fly eclosion characteristics, possibly reflecting differential effects of winter on host plant fruiting phenology. Differences in phenological sensitivity of the lower host plant trophic level to variation in environmental conditions may have cascading effects, sequentially and differentially affecting eclosion times in higher frugivore (fly) and parasitoid (wasp) trophic levels.

Temporal Dynamics of Host Use by Drosophila suzukii in California's San Joaquin Valley: Implications for Area-Wide Pest Management.

A major challenge to the area-wide management of Drosophila suzukii is understanding the fly’s host use and temporal dynamics, which may dictate local movement patterns. We determined D. suzukii’s seasonal host use in California’s San Joaquin Valley by sampling common crop and non-crop fruits in a temporal sequence of fruit ripening. We then evaluated the suitability of selected fruits as hosts. Drosophila suzukii emerged from both intact and damaged cherries during the cooler, early season period. Fly density remained low through the hot spring–summer period and re-surged as temperatures lowered in fall when the fly did not cause damage to intact peach, nectarine, plum, pear, grape, pomegranate, apple, persimmon and citrus (in order of ripening) but did emerge from the damaged fruits of these crops. The fly also emerged from two ornamental fruits (loquats and cactus) but was not found on wild plum and two endemic wild fruits (buckthorn and bitter berry). Drosophila suzukii completed development (egg to adult) on cactus, mandarin carpel, pomegranate seed, wild plum and buckthorn at survival rates similar to cherry (51.2–68.8%), whereas it had a lower survival rate on bitter cherry (33.2%), table grape (31.5%), raisin grape (26.5%), and wine grape (4.5%). The high acidity levels of grapes negatively affected the fly’s fitness. Among 10 cherry cultivars, survival rate was not affected by sugar content, but it decreased with increasing egg density per gram of fruit. Results suggest that in California’s San Joaquin Valley, the early season crops are most vulnerable, summer fruits ripen during a period of low pest pressure, and late season fruits, when damaged, serve to sustain D. suzukii’s populations in this region.

Complete chloroplast genome of Prunus emarginata and its implications for the phylogenetic position within Prunus sensu lato (Rosaceae)

Prunus emarginata is a species of Prunus native to western North America.We determined the first complete chloroplast genome of P. emarginata using genome skimming approach. The cp genome was 157,458 bp long, with a large single-copy region (LSC) of 85,567 bp and a small single-copy region (SSC) of 19,121 bp separated by a pair of inverted repeats (IRs) of 26,385 bp. It encodes 129 genes, including 84 protein-coding genes, 37 tRNA genes, and 8 ribosomal RNA genes. We also reconstructed the phylogeny of Prunus sensu lato using maximum likelihood (ML) method, including our data and previously reported cp genomes of related taxa. The phylogenetic analysis indicated that P. emarginata is closely related with Prunus subhirtella var. subhirtella and Prunus yedoensis.

Limited genetic evidence for host plant‐related differentiation in the Western cherry fruit fly, Rhagoletis indifferens

AbstractThe shift of the fruit fly Rhagoletis pomonella (Walsh) in the mid‐1800s from downy hawthorn, Crataegus mollis (Torrey & Asa Gray) Scheele, to introduced domesticated apple, Malus domestica (Borkhausen), in the eastern USA is a model for ecological divergence with gene flow. A similar system may exist in the northwestern USA and British Columbia, Canada, where Rhagoletis indifferens Curran (Diptera: Tephritidae) attacks the native bitter cherry Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae). Populations of R. indifferens have shifted and became economic pests on domesticated sweet cherry, Prunus avium (L.) L., shortly after sweet cherries were introduced to the region in the mid‐1800s. The fruiting phenologies of the two cherries differ in a similar manner as apples and hawthorns, with domesticated sweet cherries typically ripening in June and July, and bitter cherries in July and August. Here we report, however, little evidence for genetic differentiation between bitter vs. sweet cherry populations of R. indifferens or for pronounced genetic associations between allele frequencies and adult eclosion time, as has been documented for apple and downy hawthorn flies. The current findings support a previous more geographically limited survey of R. indifferens in the province of British Columbia, Canada, and an analysis of its sister species, R. cingulata, in the state of Michigan, USA, implying a lack of host‐related differentiation for flies infesting different cherry host plants. Possible causes for why host races are readily genetically detected for R. pomonella but not for R. indifferens are discussed.

Results Obtained in Breeding of Bitter Cherry Assortment at Fruit Growing Research Station Iaşi - Romania

Abstract The paper proposes the improvement of the current bitter cherry assortment with new creations made at Iaşi, adapted to the specific conditions from the NE area of Romania. For the improvement of the bitter cherry assortment with new, productive, disease resistant cultivars with fruits of good quality, resistant to cracking with different maturation stages, in 1981 at Fruit Growing Research Station (F.G.R.S.) Iaşi - Romania has begun an action of selection and promoting of some valuable genotypes of bitter cherry (existent in the spontaneous flora or in plantations from the Iaşi county), which were being planted with cultivars and other genotypes from all around the country. Following the positive and gradual selection there were selected three biotypes of bitter cherry from which two of them have been approved as new cultivars in 1994, with the names „Amar Maxut”, respectively, „Amar Galata” and the biotype „Amar R5.P10” has been registered in 2013 at the State Institute for Variety Testing and Registration Bucharest to be approved as a new cultivar. All three bitter cherry genotypes correspond to the objectives of the main assortment breeding. They have a high productivity because the natural fertility index registered values between 36.5-63.7%, the trees have a reduced vigour, they present a good resistance to frost (1-9% affected buds) and to diseases (values of I% anthracnose, 1.1-2.8%). The fruits are high quality and the maturation stages are at the extremities of the cherries maturation season.

Chilling and Host Plant/Site-Associated Eclosion Times of Western Cherry Fruit Fly (Diptera: Tephritidae) and a Host-Specific Parasitoid.

The western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is an endemic herbivore of bitter cherry, Prunus emarginata (Douglas ex Hooker) Eaton, but ∼100 years ago established on earlier-fruiting domesticated sweet cherry, Prunus avium (L.) L. Here, we determined if eclosion times of adult R. indifferens from sweet and bitter cherry differ according to the phenology of their respective host plants and if eclosion times of the host-specific parasitoid Diachasma muliebre (Muesebeck) (Hymenoptera: Braconidae) attacking bitter and sweet cherry flies differ according to the eclosion phenology of their fly hosts. Fly pupae from sweet and bitter cherry fruit were collected from sympatric and allopatric sites in Washington state, and chilled at 5°C. Because timing of eclosion in R. indifferens depends on chill duration, eclosion time in wasps could also vary with chill duration. To account for this, fly pupae were chilled for 1, 2, 2.5, 3, 4, 6, or 8 mo. Both flies and wasps eclosed earlier with longer chill durations. Eclosion times of sweet and bitter cherry flies from a sympatric site in central Washington did not differ. However, at allopatric sites in northwestern and central Washington, bitter cherry flies eclosed later than sweet and bitter cherry flies at the sympatric site. Correspondingly, D. muliebre parasitizing a more isolated bitter cherry fly population eclosed later than D. muliebre parasitizing earlier-emerging sweet and bitter cherry fly populations. These results provide evidence for D. muliebre rapidly responding to changes in host plant shifts by R. indifferens.

Antioxidant Activity of some Nutraceuticals Based on Romanian Black and Red Fruits Mixed Extracts

With content rich in polyphenols, carotenoids vitamins, minerals and many other bioactive compounds, fruits extracts from Morus nigra L. – black mulberry (blackberry) from Moraceae family, Cerasus avium (syn. Prunus avium) Moench. - bitter cherry from Rosaceae family, Cornus mas L. – cornelian cherry from Cornaceae family, may be useful as a supplementary treatment and especially in preventing many diseases which arise from action of oxidative stress. The aim of this paper is to obtain selected syrups with an increased antioxidant activity based on a mixture of fluids extracts from Morus nigra L. , Cerasus avium (syn. Prunus avium) Moench. and Cornus mas L. indigenous Romanian fruits. Fluid extracts were obtained using different extraction methods (maceration, reflux) and solvents (ethylic alcohol 40% and 70%). The obtained fluid extracts were mixed in different molar ratio and analysed for their physical-chemical properties, total polyphenols assay (Folin–Ciocalteu assay) and total antioxidative capacity by photochemiluminescence method (ACL, Analytik Jena AG procedure). The selected mixed fluid extracts with greatest content of polyphenols and antioxidant activity were used for syrups obtaining. The new obtained syrups were analysed for their physical-chemical properties (appearance, pH and relative density), polyphenols content and total antioxidative capacity. Preliminary results emphasize that syrups with highest antioxidant activity correlated with the polyphenols content would represent a possible new stimulating nutraceuticals that could be used in oxidative stress associated to different diseases. DOI: 10.5901/ajis.2015.v4n1s2p199

New records ofRhagoletisLoew, 1862 (Diptera: Tephritidae) and their host plants in western Montana, U.S.A.

Little information exists concerning the distribution of fruit flies in the genus Rhagoletis Loew, 1862 (Diptera: Tephritidae) in Montana, western U.S.A. Here, the presence of and host plant use by Rhagoletis spp. are documented in northwestern Montana. The western cherry fruit fly, Rhagoletis indifferens Curran, 1932, was abundant in the state and infested sweet cherry, Prunus avium (L.) L.; mahaleb cherry, P. mahaleb L.; tart cherry, P. cerasus L.; and bitter cherry, P. emarginata (Douglas ex Hook.) D. Dietr. (Rosaceae). Black cherry fruit fly, R. fausta (Osten-Sacken, 1877), was rare and detected only in bitter cherry. Rhagoletis berberis Curran, 1932, R. basiola (Osten-Sacken, 1873), R. tabellaria (Fitch, 1855), and apple maggot, R. pomonella (Walsh, 1867), were all recorded for the first time in Montana. Flies in Montana were mainly reared from previously reported species of host plants, but new host records also documented include, R. indifferens from black hawthorn, Crataegus douglasii Lindl. (Rosaceae), a new Montana record; R. berberis from sweet cherry; R. basiola from baldhip rose, Rosa gymnocarpa Nutt. (Rosaceae); and R. tabellaria from Hooker's fairy bells, Prosartes hookeri Torr. (Liliaceae). Rhagoletis pomonella, likely introduced into the western U.S., was reared from C. douglasii but not from the relatively few domesticated apple trees, Malus domestica Borkh., (Rosaceae) sampled. The findings extend the known geographic ranges of four Rhagoletis species and indicate that some flies in northwestern Montana have the ability to survive and develop in alternative and novel hosts, consistent with findings for populations in other areas of the western U.S.

First Report of Cherry mottle leaf virus Infecting Cherry in China

Cherry mottle leaf virus (CMLV) is a member of the genus Trichovirus (family Betaflexiviridae). CMLV infects several species of the genus Prunus including cherry (Prunus avium) and peach (P. persica) (2,3). It is spread via budding and grafting with infected wood and can be transmitted from infected bitter cherry (P. emarginata), or infected but symptomless peach trees to healthy sweet cherry trees by the bud mite (Eriophyes inaequalis) (1). On susceptible sweet cherry cultivars, CMLV causes symptoms such as chlorotic mottle-leaf pattern, distortion, puckering of younger leaves, and small fruits that ripen late (1), which may lead to severe economic losses in some cultivars. Cherry is one of the most important fruit tree species in North China, and Shandong Province is one of the major cherry production areas. In June 2013, a survey of possible CMLV presence was conducted in a cherry orchard planted in 1996 in Zoucheng city, Shandong. The sweet cherry cultivars in this orchard included Black Tartarian, Bing, Hongdeng (a hybrid between cvs. Napoleon and Huangyu), and others; the rootstock cultivar utilized to graft these cultivars was mountain cherry (P. tomentosa). During the survey, characteristic symptoms on leaves such as leaf mottling, distortion, and puckering similar to those caused by CMLV were observed on some trees of the cv. Hongdeng, and the symptomatic trees accounted for ~10% of the total trees of this cultivar. Five symptomatic cherry leaf samples and three healthy-looking cherry leaf samples of cv. Hongdeng were collected. Total RNA extracted from the leaf samples using RNeasy plant mini kit (Qiagen Inc., Valencia, CA) was subjected to first strand cDNA synthesis with the reverse primer CMLV-3R (5'-CTCGAGAACACAGAGATTTGTCGAGAC-3', sequence in italics indicates restriction site XhoI) and M-MLV reverse transcriptase (Promega, Madison, WI) according to the manufacturer's instruction. The cDNA was then used as template in the PCR assay using primers CMLV-5F (5'-GGATCCATGTCGGCGCGATTGAATC-3', sequence in italics indicates restriction site BamHI) and CMLV-3R, which amplify the genome fragment including the capsid protein gene of CMLV. The expected PCR product ~590 bp was amplified from all five symptomatic samples, while no such PCR product was amplified from the symptomless samples. The PCR products were cloned into pMD18-T vector (TaKaRa, Dalian, China). Three positive clones for each of the five amplicons were sequenced in both directions. Sequence alignment and nucleotide BLAST analysis of the sequences revealed that they were 99% to 100% identical to the corresponding capsid protein gene sequence of a cherry isolate of CMLV (GenBank Accession No. AF170028) and 85% identical with that of the peach wart strain of CMLV (KC207480). Our results confirm the infection of cherry trees by CMLV in Shandong. To our knowledge, this is the first report of CMLV on cherry in China. As the spread of CMLV by mite vector in the field is rare (1), and no bud mite outbreak had occurred in this orchard in the past years, so it is possible that virus-infected propagation materials are largely responsible for the spread of this virus. Considering the importance of cherry cultivation in China, this report prompts the need to survey the occurrence of this virus in Shandong and other provinces, and the need to develop more effective management strategies such as the use of certified virus-free nursery stocks to reduce the impact of CMLV.

Evaluating correlative and mechanistic niche models for assessing the risk of pest establishment

Insect pests pose a great threat to global food security. Improved methods for assessment of the risk of pest establishment are needed to enhance informed decision‐making, to develop cost‐effective pest management strategies, and to design quarantine policies for preventing the spread of pests. We evaluated the capabilities of a correlative and a process‐based mechanistic niche model, and their combination, to assess the risk of pest establishment. The correlative model MaxEnt and the process‐based mechanistic model CLIMEX were used to assess the risk of establishment of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae) in California. We integrated R. indifferens occurrence records and spatial environmental variables using MaxEnt to assess the potential risk of establishment of this pest. The CLIMEX model was developed using eco‐physiological tolerances of R. indifferens. The predictive performance of the MaxEnt model improved by including the host species' distribution and Ecoclimatic Index generated using the CLIMEX model. The best model predicted no risk for R. indifferens establishment in the Central Valley around the areas where sweet cherries are produced in California. Most of the high to very high risk areas for R. indifferens were predicted in northern parts of California and the Sierra Nevada Mountains, where the fly exists on its native host, bitter cherry [Prunus emarginata (Douglas) Eaton]. Precipitation of driest quarter, degree days with average temperatures ≥8.3°C, degree days with average temperatures ≤5°C, and mean diurnal range in temperature were the strongest predictors of R. indifferens distribution in western North America. We showed that the predictive power of correlative niche models can be improved by including outputs from the process‐based mechanistic niche models. Overall results suggest that R. indifferens is unlikely to establish in the commercial cherry‐growing areas in the Central Valley of California, largely because heat stress is too high and chilling requirement in those areas is not met.

Seasonal Distributions of the Western Cherry Fruit Fly (Diptera: Tephritidae) Among Host and Nonhost Fruit Trees

Seasonal distributions of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in sweet cherry ( Prunus avium (L.) L.) (major host), black hawthorn (occasional developmental host) ( Crataegus douglasii Lindley), and other trees were determined in a ponderosa pine ecosystem in Washington state, USA. The hypothesis that most fly dispersal from cherry trees occurs after fruit senesce or drop was tested, with emphasis on movement to black hawthorn trees. Sweet cherry fruit developed earlier than black hawthorn, bitter cherry (common host), choke cherry, and apple fruit. Flies were usually captured first in sweet cherry trees but were caught in bitter cherry and other trees throughout the season. Peak fly capture periods in sweet cherry began around the same time or slightly earlier than in other trees. However, peak fly capture periods in black hawthorn and other nonsweet cherry trees continued after peak periods in sweet cherry ended, or relative fly numbers within sweet cherry declined more quickly than those within other trees. Larvae were reared from sweet and bitter cherry but not black hawthorn fruit. Results provide partial support for the hypothesis in that although R. indifferens commonly disperses from sweet cherry trees with fruit, it could disperse more, or more flies are retained in nonsweet cherry trees after than before sweet cherries drop. This could allow opportunities for the flies to use other fruit for larval development. Although R . indifferens infestation in black hawthorn was not detected, early season fly dispersal to this and other trees and fly presence in bitter cherry could make fly management in sweet cherry difficult.

Niche differentiation and colonization of a novel environment by an asexual parasitic wasp

How do asexual taxa become adapted to a diversity of environments, and how do they persist despite changing environmental conditions? These questions are linked by their mutual focus on the relationship between genetic variation, which is often limited in asexuals, and the ability to respond to environmental variation. Asexual taxa originating from a single ancestor present a unique opportunity to assess rates of phenotypic and genetic change when access to new genetic variation is limited to mutation. Diachasma muliebre is an asexual Hymenopteran wasp that is geographically and genetically isolated from all sexual relatives. D. muliebre attack larvae of the western cherry fruit fly (Rhagoletis indifferens), which in turn feed inside bitter cherry fruit (Prunus emarginata) in August and September. R. indifferens has recently colonized a new host plant with an earlier fruiting phenology (June/July), domesticated sweet cherries (P. avium), and D. muliebre has followed its host into this temporally earlier niche. We tested three hypotheses: 1) that all D. muliebre lineages originate from a single asexual ancestor; 2) that different D. muliebre lineages (as defined by unique mtDNA haplotypes) have differentiated on their ancestral host in an important life-history trait, eclosion timing; and 3) that early-eclosing lineages have preferentially colonized the new sweet cherry niche. We find that mitochondrial COI and microsatellite data provide strong support for a single ancestral origin for all lineages. Furthermore, COI sequencing revealed five mitochondrial haplotypes among D. muliebre, and individual wasps possessing one distinctive mitochondrial haplotype (haplotype II) eclosed as reproductive adults significantly earlier than wasps with all other haplotypes. In addition, this early-eclosing lineage of D. muliebre is one of two lineages that have colonized the P. avium habitat, consistent with the preferential colonization hypothesis. These data suggest that D. muliebre has evolved adaptive phenotypic variation despite limited genetic variation, and that this variation has subsequently allowed an expansion of some wasps into a novel habitat. The D. muliebre system may allow for in-depth study of adaptation and long-term persistence of asexual taxa.

Seedbanks, germination and early survival of bitter cherry (Prunus emarginata) in coastal British Columbia

Early successional species that rely on a seedbank differ in life history from most other species of forested landscapes. Prunus emarginata (bitter cherry) is a shade-intolerant tree that can develop in abundance (>20,000 stems ha−1) from a seedbank after disturbance in forests along the northwest coast of North America. It can inhibit growth of commercially valuable conifers, but also provide habitat diversity and appearance-grade wood. We determined (1) seed populations in soil of 15 stands 1 to 140-plus years old (2) emergence and survival from planted seed, along with environmental conditions, for three years in open clearcut, forest edge, and under closed canopy on mineral soil or organic seedbeds and with and without cages to exclude animals, and (3) effects of light and temperature on germination in controlled environments. There, seeds were cold-stratified (0 or 70days), then exposed to temperature (10, 17, or 25°C) and photoperiod (0, 14h) treatments, which were interrupted with a second (90day) cold period. Population densities of filled seed were greatest in 51–75year-old stands (>106ha−1). Of emergence in the field, 0% was in year 1, 79% in year 2 and 21% in year 3; 81% of emergence occurred in the open, 19% at the edge, and 0% under the canopy. Emergence in the open was greatest in caged, mineral soil plots. Survival of emerged seedlings was 18% in the open, but 0% at the forest edge. Seedling emergence occurred mainly in April. In controlled environments, germination began during the second cold stratification, suggesting alternating warm and cold periods were needed to overcome seed dormancy. Germination was greatest at 17°C, but only in combination with the first cold stratification and light. Midday seedbed temperatures partly explain the timing and location of emergence, but diurnal temperature amplitude may be a more important cue of canopy removal. Large accumulations of seed in soil, combined with low emergence and survival rates, can account for the high population densities of seedlings sometimes observed following disturbance. Canopy removal is necessary to maintaining P. emarginata in the conifer-dominated landscape, and the long-lived seedbank allows it to persist between disturbances.

Differences in Body Size and Egg Loads of Rhagoletis indifferens (Diptera: Tephritidae) From Introduced and Native Cherries

The western cherry fruit fly, Rhagoletis indifferens Curran, infests introduced, domesticated sweet [Prunus avium (L.) L.], and tart cherries (Prunus cerasus L.) as well as native bitter cherry, Prunus emarginata (Douglas) Eaton. Bitter cherries are smaller than sweet and tart cherries and this could affect various life history traits of flies. The objectives of the current study were to determine 1) if body size and egg loads of flies infesting sweet, tart, and bitter cherries differ from one another; and 2) if any observed body size differences are genetically based or caused by the host fruit environment. Pupae and adults of both sexes reared from larval-infested sweet and tart cherries collected in Washington and Montana were larger than those reared from bitter cherries. In addition, flies of both sexes caught on traps in sweet and tart cherry trees were larger than those caught in bitter cherry trees and females trapped from sweet and tart cherry trees had 54.0-98.8% more eggs. The progeny of flies from naturally-infested sweet and bitter cherries reared for one generation in the laboratory on sweet cherry did not differ in size. The same also was true for progeny of sweet and bitter cherry flies reared in the field on bitter cherry. The results suggest that the larger body sizes of flies from sweet and tart cherries than bitter cherries in the field are caused by host fruit and not genetic factors.

Host plant use by apple maggot, western cherry fruit fly, and other Rhagoletis species (Diptera: Tephritidae) in central Washington state

Host plant use by apple maggot fly, Rhagoletis pomonella (Walsh), 1867, western cherry fruit fly, Rhagoletis indifferens Curran, 1932, and other Rhagoletis species (Diptera: Tephritidae) in five cities or towns and several habitats of different commercial importance within south central Washington state was determined in 2004 to 2006. Rhagoletis pomonella larvae infested 0 to 1.6% of non-commercial apple trees, Malus domestica (Borkh.) Borkh., and 0 to 22.5% of wild black hawthorn, Crataegus douglasii Lindl. (Rosaceae), the first data showing R. pomonella has established within this part of the state. Rhagoletis indifferens infested 81.8 to 100% of non-commercial sweet and sour cherry trees (Prunus avium (L.) L. and Prunus cerasus L.) (0% in one area) and 21.7 to 94.7% of wild bitter cherry trees, Prunus emarginata (Dougl. ex Hook.) D. Dietr. (Rosaceae). Rhagoletis zephyria Snow, 1894, Rhagoletis basiola (Osten Sacken), 1877, Rhagoletis tabellaria (Fitch), 1855, Rhagoletis berberis Curran, 1932, and Rhagoletis completa Cresson, 1929 infested 0 or 15.4 to 100% of their normal host plants. In south central Washington, the host breadth of R. pomonella is narrow perhaps because of the hot and dry conditions, low fly densities, and low host abundance outside of orchards. Here, R. pomonella likely can be managed to meet the strict quarantine requirements of apple export. Rhagoletis indifferens management can be confined to sweet and sour cherry trees. Responses of various Rhagoletis species to plant cues and survival of flies in dry climates need to be determined to understand patterns of host use and population densities in Washington.