油菜田害虫调查及蚜虫防治药剂筛选

田间调查试验表明,合肥市油菜田害虫的发生种类有15种,主要害虫为蚜虫类、油菜潜叶蝇Phytomyza horticola、小菜蛾Plutella maculipennis和菜青虫Pieris rapae。其中,以蚜虫类危害最重,全生育期在冬、春季各有一个峰值。油菜苗期以萝卜蚜、小菜蛾危害较重,后期以桃蚜Myzus persicae、油菜潜叶蝇危害较重。蚜虫防治药剂筛选试验表明,70%吡虫啉水分散粒剂防治蚜虫药效高,持效期长,且对油菜安全,10%烯啶虫胺可溶液剂和25%吡蚜酮可湿性粉剂防效也较好,可作为70%吡虫啉水分散粒剂的轮换药剂。     

Probing behavior of bird cherry-oat aphid Rhopalosiphum padi (L.) on native bird cherry Prunus padus L. and alien invasive black cherry Prunus serotina Erhr. in Europe and the role of cyanogenic glycosides

The probing behavior of bird cherry-oat aphid Rhopalosiphum padi was studied on its natural winter host in Europe, the bird cherry Prunus padus, and on the invasive black cherry Prunus serotina, on which spring generations of R. padi do not survive. The EPG-recorded behavior of R. padi on bird cherry and black cherry showed differences in crucial aspects of probing and feeding. The period of the pre-phloem penetration was twice as long and rarely interrupted in aphids on bird cherry as opposed to aphids on black cherry. On black cherry, there was a considerable delay between finding and accepting the phloem. Aphids that had sampled phloem sap either refused to ingest it or the ingestion periods were very short. Amygdalin and prunasin (cyanogenic glycosides present in leaves of Prunus) seriously impeded ingestion activities when applied in pure sucrose diet. The role of amygdalin and prunasin in winter host plant selection and host alternation in R. padi is discussed.     

Genetic structure of cherry fruit fly (Rhagoletis cingulata) populations across managed,unmanaged, and natural habitats

The cherry fruit fly (CFF), Rhagoletis cingulata Loew (Diptera: Tephritidae: Trypetini), is endemic to eastern North America and Mexico, where its primary native host is black cherry [Prunus serotina Ehrh. (Rosaceae)]. Cherry fruit fly is also a major economic pest of the fruit of cultivated sweet (Prunus avium L.) and tart (Prunus cerasus L.) cherries. Adult CFF that attack wild black cherry and introduced, domesticated cherries in commercial and abandoned orchards are active at different times of the summer, potentially generating allochronic isolation that could genetically differentiate native from sweet and tart CFF populations. Here, we test for host‐related genetic differences among CFF populations in Michigan attacking cherries in managed, unmanaged, and native habitats by scoring flies for 10 microsatellite loci. Little evidence for genetic differentiation was found across the three habitats or between the northern and southern Michigan CFF populations surveyed in the study. Local gene flow between native black cherry, commercial, and abandoned orchards may therefore be sufficient to overcome seasonal differences in adult CFF activity and prevent differentiation for microsatellites not directly associated with (tightly linked to) genes affecting eclosion time. The results do not support the existence of host‐associated races in CFF and imply that flies attacking native, managed, and unmanaged cherries should be considered to represent a single population for pest management purposes.     

Male oriental fruit moth response to a combined pheromone-based attracticide formulation targeting both oriental fruit moth and codling moth (Lepidoptera: Tortricidae)

Combined attracticide formulations targeting Oriental fruit moth, Grapholita molesta (Busck), and codling moth, Cydia pomonella (L.), were tested in a field trapping experiment. Capture of male codling moths in traps baited with the combined formulation was reduced compared with traps baited with the codling moth formulation alone, whereas capture of male Oriental fruit moth was increased compared with traps baited with the Oriental fruit moth formulation alone. Subsequent wind tunnel experiments showed that a single locus of the mixed attracticide formulation or close parallel presentation of the two formulations enhanced source contact by male Oriental fruit moths but did not influence earlier behaviors. However, the two formulations presented in a serial arrangement to Oriental fruit moth males in the wind tunnel resulted in enhanced lock-on, upwind flight, and source contact behaviors. In addition, male Oriental fruit moths remained on mixed pheromone droplets of the paste matrix longer than on droplets of the Oriental fruit moth formulation alone. The increased time spent on the mixed droplet was correlated with a more rapid poisoning and a greater proportion of poisoned males compared with males exposed to the Oriental fruit moth attracticide alone. These results demonstrate that a combined attracticide formulation will have different effects on each of the targeted species. It is anticipated that, due to decreased attractiveness, a combined formulation would be less effective against the codling moth. However, a mixed formulation, due to increased attractiveness and toxicity, could be more effective against the Oriental fruit moth under field conditions.     

Improved production of erythromycin by Saccharopolyspora erythraea by various plant oils

Various plant oils (50 g l^–1) increased the production of erythromycin by Saccharopolyspora erythraea. Maximum titer of erythromycin in media containing black cherry kernel, walnut, rapeseed, olive and cottonseed oils and control medium were 3.5, 2.8, 2.6, 2.1, 1.9, 0.7 g l^–1, respectively. Erythromycin production media containing rapeseed or cottonseed oil was growth-dependent but not in other media used.     

Habitat isolation affects plant–herbivore–enemy interactions on cherry trees

Understanding the interactions between herbivores and natural enemies in fragmented landscapes is essential for conservation biological control. Studies including multiple enemies affecting multiple herbivores, plant damage and growth are needed. Here, we separated independent effects of (1) isolation of cherry trees from woody habitat and (2) the amount of woody habitat in the surrounding landscape (500 m buffers) on interactions between different groups of herbivores with their natural enemies and resulting changes in the growth of young cherry trees. Most predatory arthropods declined with habitat isolation, except some aphid predators (ladybeetles and hoverflies). Herbivores either increased with isolation (herbivorous beetles) or showed no significant response (aphids). In contrast, the amount of woody habitat in the landscape was not relevant for herbivore–enemy interactions at the investigated scale. Plant growth was affected by bottom-up (nutrient availability) and top-down (aphid density) forces but did not change significantly with habitat amount or isolation. We conclude that herbivores can be released from natural enemies at isolated sites, in accordance with the hypothesis that habitat connectivity improves pest control. However, each herbivore group responded differently to the landscape context and had contrasting effects on the same host plant, demonstrating the difficulty to predict landscape effects on plant growth.     

Studies on water transport through the sweet cherry fruit surface: IX. Comparing permeability in water uptake and transpiration

Water uptake and transpiration were studied through the surface of intact sweet cherry (Prunus avium L.) fruit, exocarp segments (ES) and cuticular membranes (CM) excised from the cheek of sweet cherry fruit and astomatous CM isolated from Schefflera arboricola (Hayata) Hayata, Citrus aurantium L., and Stephanotis floribunda Brongn. leaves or from Lycopersicon esculentum Mill. and Capsicum annuum L. var. annuum Fasciculatum Group fruit. ES and CM were mounted in diffusion cells. Water (deionized) uptake into intact sweet cherry fruit, through ES or CM interfacing water as a donor and a polyethyleneglycol (PEG 6000, osmotic pressure 2.83 MPa)-containing receiver was determined gravimetrically. Transpiration was quantified by monitoring weight loss of a PEG 6000-containing donor (2.83 MPa) against dry silica as a receiver. The permeability coefficients for osmotic water uptake and transpiration were calculated from the amount of water taken up or transpired per unit surface area and time, and the driving force for transport. Permeability during osmotic water uptake was markedly higher than during transpiration in intact sweet cherry fruit (40.2-fold), excised ES of sweet cherry fruit (12.5- to 53.7-fold) and isolated astomatous fruit and leaf CM of a range of species (on average 23.0-fold). Partitioning water transport into stomatal and cuticular components revealed that permeability of the sweet cherry fruit cuticle for water uptake was 11.9-fold higher and that of stomata 56.8-fold higher than the respective permeability during transpiration. Increasing water vapor activity in the receiver from 0 to 1 increased permeability during transpiration across isolated sweet cherry fruit CM about 2.1-fold. Permeability for vapor uptake from saturated water vapor into a PEG 6000 receiver solution was markedly lower than from liquid water, but of similar magnitude to the permeability during self-diffusion of ³H₂O in the absence of osmotica. The energy of activation for self-diffusion of water across ES or CM was higher than for osmotic water uptake and decreased with increasing stomatal density. The data indicate that viscous flow along an aqueous continuum across the sweet cherry fruit exocarp and across the astomatous CM of selected species accounted for the higher permeability during water uptake as compared to self-diffusion or transpiration.     

Potential for high hydrostatic pressure processing to control quarantine insects in fruit

Tests were conducted to determine the potential for high hydrostatic pressure (HPP) to control codling moth, Cydia pomonella (L.), and western cherry fruit fly, Rhagoletis indifferens Curran. Apples (Malus spp.) with codling moth larvae or eggs were treated at 24 and 72 h, respectively, after infestation at a series of pressures between 14,000 and 26,000 pounds per inch2 (psi). Survivorship was determined the next day for larvae and after 10 d for eggs. Codling moth eggs were more tolerant of HPP treatment than larvae. Mortality of larvae was 97% at 22,000 psi, whereas mortality of eggs at this dose was 29% and not significantly different from the untreated controls. In a second study, no codling moth eggs hatched at any high pressure treatment between 30,000 and 80,000 psi, indicating these pressures were lethal. Various stages of western cherry fruit fly were treated at pressures from 10,000 to 45,000 psi, and survivorship was determined after 24 h. Eggs and third instars were more tolerant of HPP than the first and second instars. Mortality was 100% in western cherry fruit fly eggs and larvae at pressures > or =25,000 psi. Apple and sweet cherry quality after high pressure treatment was poor, but high pressure may have applications to control quarantine pests in other fruits.     

Comparison between woody indexing and a rapid hybridisation assay for the diagnosis of little cherry disease in cherry trees*

Sweet cherry (Prunus avium) and sour cherry (Prunus cerasus) trees from orchards in the Kootenay and Okanagan Valleys of British Columbia, Canada were assayed for the presence of little cherry disease by three different methods: Northern blot analysis of double-stranded RNA, woody indexing for fruit symptoms on sweet cherry cv. Lambert, and woody indexing for foliar symptoms on cv. Canindex 1. Results of the three methods were in agreement for 85% of the samples. Of the 78 orchard trees tested, double-stranded RNA isolated from 48 trees hybridised with a radiolabeled cloned probe specific for little cherry disease. When the 48 trees were tested by woody indexing, buds from 41 trees induced fruit symptoms on cv. Lambert, but only 32 yielded foliar symptoms on cv. Canindex 1 under the conditions of the experiment. Of the 30 orchard trees that did not yield a positive response to the Northern blot analysis, 26 samples were negative on cv. Lambert and 26 were negative on cv. Canindex 1. Northern blot analysis of the 78 cv. Lambert indicator trees revealed that there was an absolute correlation between the presence of little cherry disease-associated double-stranded RNA and the development of typical little cherry disease symptoms on the indicator trees. Reliability of woody indexing of orchard samples was impaired by poor transmission of the disease from the inoculating bud to the indicator tree. Woody indexing with cv. Canindex 1 was particularly prone to a large number of apparently erroneous negative results. Of the three protocols used, diagnosis of little cherry disease by Northern blot analysis was found to be the most reliable and offered a greatly accelerated means of diagnosis.     

The regulation of sweet cherry fruit abscission by polar auxin transport

Inconsistency of cropping is an important problem for UK sweet cherry production. Premature fruit abscission in Prunus can reduce yields severely, however, the environmental cues and hormonal signals that trigger abscission have not been identified. Auxin (IAA) is known to delay abscission by reducing the sensitivity of cells in the abscission zone to ethylene, a promoter of abscission. Therefore, the capacity for polar auxin transport (PAT) through sweet cherry pedicels was examined in relation to fruit abscission. Cherry ‘spurs’ (short shoots) with similar leaf areas and different fruit numbers were phloem-girdled to restrict assimilate movement. Abscission from spurs with many fruit (eight or more) occurred within 14 days of girdling, whereas abscission from spurs with few (two) fruit was minimal. The pedicels’ capacity for PAT in spurs with different fruit numbers was determined 1, 3 and 9 days after girdling (DAG). Fruit were analysed for endogenous IAA concentration 3, 5, 7 and 9 DAG. PAT inhibitors 2,3,5-triiodobenzoic acid or 1-N-naphthylphtalamic acid were applied to pedicels of fruit not expected to abscise, i.e. on spurs with few fruit. The effect of these inhibitors on fruit abscission was determined 14 DAG. The proportion of the transported [³H]-IAA was lower from the outset in pedicels from spurs with many fruit. By 9 DAG, symptoms of fruit abscission were apparent and 40% less [³H] -IAA was transported through pedicels on spurs with many fruit. Fruit endogenous IAA concentrations were similar in the two groups of spurs. Application of PAT inhibitors shortly after girdling increased fruit abscission by 30%. The results suggest that although a decline in PAT is not the only cause of fruit abscission, the maintenance of PAT contributes to fruit retention.     

蚜虫对设施辣椒产量和品质的影响

【目的】探讨不同蚜害等级危害对设施辣椒产量和品质的影响,为设施蔬菜的科学防控、按质定价及制定蚜虫经济阈值提供参考。【方法】通过田间蚜虫量调查,进行蚜害分级,并测定不同蚜害等级下辣椒叶片和果实的SPAD值,采收后记录单株果数,称重,计算座果率及单株果重等产量指标;同时测定不同蚜害等级下辣椒果实可溶性蛋白、可溶性糖、维生素C含量等品质指标。【结果】当蚜害等级达Ⅲ级及以上时,即可导致设施辣椒产量和品质相关指标明显下降,且随着蚜害等级增加,下降越显著。当蚜害等级达Ⅴ时,辣椒叶片和果实的SPAD值比对照分别下降了38.29%和29.49%,辣椒座果率比对照下降了21.28%,单株果重比对照下降了40.09%,且1、2级果数量明显减少;辣椒可溶性糖、维生素C含量比对照分别下降了35.66%、39.29%,可溶性蛋白含量略有下降,但与对照无显著差异。【结论】当蚜害等级为Ⅲ级以上,即株虫量为50头以上时,辣椒产量、品质出现明显下降,因此,当辣椒整株虫量达50头以上时要及时进行蚜虫防治。     

Enhancing of erythromycin production by <Emphasis Type="Italic">Saccharopolyspora erythraea</Emphasis> with common and uncommon oils

The enhancing effect of various concentrations of 18 oils and a silicon antifoam agent on erythromycin production by Saccharopolyspora erythraea was evaluated in a complex medium containing soybean flour and dextrin as the main substrates. The oils used consisted of sunflower, pistachio, cottonseed, melon seed, water melon seed, lard, corn, olive, soybean, hazelnut, rapeseed, sesame, shark, safflower, coconut, walnut, black cherry kernel and grape seed oils. The biomass, erythromycin, dextrin and oil concentrations and the pH value were measured. Also, the kinds and frequencies of fatty acids in the oils were determined. The productivity of erythromycin in the oil-containing media was higher than that of the control medium. However, oil was not suitable as a main carbon source for erythromycin production by S. erythraea. The highest titer of erythromycin was produced in medium containing 55 g/l black cherry kernel oil (4.5 g/l). The titers of erythromycin in the other media were also recorded, with this result: black cherry kernel > water melon seed > melon seed > walnut > rapeseed > soybean > (corn = sesame) > (olive = pistachio = lard = sunflower) > (hazelnut = cotton seed) > grape seed > (shark = safflower = coconut). In media containing various oils, the hyphae of S. erythraea were longer and remained in a vegetative form after 8 days, while in the control medium, spores were formed and hyphae were lysed.     

Variability in host-plant quality for the larvae of a polyphagous insect folivore in midseason: the impact of light on three deciduous sapling species

We examined the effects of light availability on the suitability of foliage from red maple (Acer rubrum L.) (Aceraceae), black cherry (Prunus serotina Ehrhart) (Rosaceae), and sassafras [Sassafras albidum (Nuttall) Nees (Lauraceae)] for the larvae of the promethea moth, Callosamia promethea Drury (Lepidoptera: Saturniidae), in midseason. We identified replicate sun- and shade-grown saplings of red maple, black cherry, and sassafras from naturally growing populations in the field. Foliage collected from the experimental saplings was bioassayed using early instars of the promethea moth and assayed for nitrogen and carbon content. Promethea moth-larval performance and survivorship was highest on sassafras, intermediate on black cherry, and lowest on red maple. Larvae feeding on foliage from plants grown in the sun performed better than from those grown in the shade; the effect of light did not depend on sapling species. Foliar nitrogen content varied among the sapling species and was higher, overall, in foliage from plants grown in the sun. Nitrogen concentration related strongly and positively with larval performance and accounted for a great deal of the variation in performance both among the sapling species and between the sun and shade treatments. During midseason, foliar nitrogen content is determined by light availability, it varies among sapling species, and it is likely the primary constituent determining host quality for folivores on these sapling species.     

Cloning,expression, and characterization of sorbitol transporters from developing sour cherry fruit and leaf sink tissues

The acyclic polyol sorbitol is a primary photosynthetic product and the principal photosynthetic transport substance in many economically important members of the family Rosaceace (e.g. almond [Prunus dulcis (P. Mill.) D.A. Webber], apple [Malus pumila P. Mill.], cherry [Prunus spp.], peach [Prunus persica L. Batsch], and pear [Pyrus communis]). To understand key steps in long-distance transport and particularly partitioning and accumulation of sorbitol in sink tissues, we have cloned two sorbitol transporter genes (PcSOT1 and PcSOT2) from sour cherry (Prunus cerasus) fruit tissues that accumulate large quantities of sorbitol. Sorbitol uptake activities and other characteristics were measured by heterologous expression of PcSOT1 and PcSOT2 in yeast (Saccharomyces cerevisiae). Both genes encode proton-dependent, sorbitol-specific transporters with similar affinities (K(m) sorbitol of 0.81 mM for PcSOT1 and 0.64 mM for PcSOT2). Analyses of gene expression of these transporters, however, suggest different roles during leaf and fruit development. PcSOT1 is expressed throughout fruit development, but especially when growth and sorbitol accumulation rates are highest. In leaves, PcSOT1 expression is highest in young, expanding tissues, but substantially less in mature leaves. In contrast, PcSOT2 is mainly expressed only early in fruit development and not in leaves. Compositional analyses suggest that transport mediated by PcSOT1 and PcSOT2 plays a major role in sorbitol and dry matter accumulation in sour cherry fruits. Presence of these transporters and the high fruit sorbitol concentrations suggest that there is an apoplastic step during phloem unloading and accumulation in these sink tissues. Expression of PcSOT1 in young leaves before completion of the transition from sink to source is further evidence for a role in determining sink activity.     

Assessment of cultivated cherry germplasm in Iran by multivariate analysis

Key message

This work is an important step in the conservation of genetic cherry resources, which showed distinctive and interesting agronomical characters. Also it introduces suitable genotypes for cultivation and breeding studies.

Abstract

The purpose of this study was to characterize cherry germplasm that is cultivated in Iran. Thirty-three morphopomological parameters were studied in this germplasm, consisting of 70 cherry genotypes (41 sweet cherry, 24 sour cherry and 5 duke cherry genotypes). A wide variation was found in blooming time, ripening time, fruit weight, fruit color, anthocyanin, total soluble solids (TSS), titratable acidity (TA), fruit dimensions and flesh firmness and stone size. There were close positive correlations between fruit weight and fruit dimensions, and between fruit weight and fruit stalk weight, fruit flesh firmness and cracking and also a negative correlation between pH and TA. Dendrogram gave a clear separation between the sour, duke and sweet cherry species and also showed existing intraspecific morphological variation. Based on fruit size and organoleptic properties, the sweet cherry genotypes ‘Siah-Mashhad’, ‘Takdaneh-Mashhad’, ‘Shabestar’, ‘Siah-Daneshkade’, ‘Ghazvin’ and ‘Droongezna’ are recommended for fresh consumption. Good fruit chemical composition and late-ripening time stands out genotypes ‘Dirres-Italia’, ‘Dirres-Pardis’, ‘Maremoot’, ‘Abardeh’ and ‘Rorshon’ and make them suitable for processing. Also, ‘Gilas46’ and ‘Gilas49’ were substantially late-ripening, a characteristic that makes these genotypes highly suitable for breeding studies in case of ripening time. Furthermore, sour cherries ‘Hashtgerd2’ and ‘Hashtgerd3’ and duke cherries ‘Pardis1’ and ‘Pardis3’ were the best genotypes. This work is an important step in the conservation of genetic cherry resources in Iran, which showed distinctive and interesting agronomical characters such as low susceptibility to fruit cracking, high levels of total soluble solids, early fruit maturity and high fruit quality.     

Habitat-specific flight period in the cherry fruit fly Rhagoletis cingulata (Loew) (Diptera: Tephritidae)

Flight periods of the cherry fruit fly, Rhagoletis cingulata (Loew), were compared in the major sweet and tart cherry-growing regions of Michigan, among neglected orchards, managed orchards, and natural areas containing the ancestral host, black cherry. Traps were deployed from early June to late September 2005 and 2006. Captures indicated that cherry fruit fly has an early flight (June-July) in neglected orchards, a mid-season flight peaking immediately after harvest (June-August) in managed orchards, and an extended flight covering most of the season (June-September) in natural areas. We found that the period of fruit infestation mirrored the flight period in neglected and managed orchards. In natural areas, we found infestation late in the season only. The relative emergence periods for adults reared from pupae collected from the three habitats and maintained under the same conditions coincided with adult flight periods for each habitat. We also studied factors related to fruit availability that may have a role in shaping the flight periods. Fruit abundance decreased rapidly early in the season in neglected orchards, whereas in managed orchards, fruit left after harvest remained on the trees until late August. Measurements of fruit size and skin firmness revealed that fly activity in neglected and managed orchards began immediately after fruit increased in size and skin firmness decreased, whereas in natural areas, the flight began before fruit matured. In managed orchards, fruit harvest and insecticide sprays likely maintain the late flight period of resident fly populations by preventing the use of fruit earlier in the season. However, a significant proportion of these resident flies may still emerge before harvest and increase the risk of costly fruit infestation.     

Feeding substrates and behaviors of Western cherry fruit fly (Diptera: Tephritidae)

A study was conducted to determine the abundance of potential foods and the feeding substrates and behaviors of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in 2005, 2006, and 2007 in central Washington state. Aphid colonies with honeydew, a presumed food source for flies, were not seen on randomly selected branches of sweet cherry trees, Prunus avium L., but leaves with cherry juice, fruit that were damaged, and leaves with bird feces were commonly seen, especially later in the season. Grazing, a behavior in which the mouthparts rapidly move up and down and touch plant surfaces without discrete substances visible to the human eye, was seen more frequently in flies on leaves than on fruit. Grazing occurred more frequently than feeding on extrafloral nectaries (EFNs) on leaf petioles, cherry juice on leaves, and bird feces on leaves. The percentages of females and males that grazed on leaves were not different in 2 of 3 yr, but the percentage of females that grazed was higher in a third year. Percentages of female and male flies that fed on EFNs, cherry juice, and bird feces did not differ. More flies grazed the tops than bottoms of leaves. Flies also grazed on leaves of apple, pear, and grape. The results support the hypotheses that R. indifferens feeds mostly on leaves rather than fruit and that leaf surfaces may be the main feeding substrates for R. indifferens throughout the season.     

Environmental conditions affect pectin solubilization in cherry tomato fruits grown in two experimental Mediterranean greenhouses

Considering the economic importance of the tomato and its nutritional benefits for human health, we studied how different environmental factors [temperature, solar radiation and vapour–pressure deficit (VPD)] influenced the pectin solubilization and the calcium concentration in cherry tomato fruits (Solanum lycopersicum cv. Naomi) grown in two experimental greenhouses: improved parral type (low-technology) and multispan type (high-technology). For three years (2004, 2005 and 2006), three fruit samples were taken over the entire production period: at the beginning of harvest [16 weeks after transplanting (WAT)], at mid-harvest (26 WAT), and at the end of harvest (35 WAT). Values for temperature, solar radiation, and VPD peaked in the third sampling in both greenhouses during the three years, being higher in the parral greenhouse during the production cycle. No-market production and peroxidation indicators [measured as H₂O₂ and malondialdehyde (MDA) concentrations] significantly increased at the end of the productive period in both greenhouses, indicating the presence of oxidative stress caused by the rise in temperature, solar radiation, and VPD, which was more pronounced in the parral greenhouse. Water-soluble pectins, pectate, and protopectin contents were measured, revealing an increase in the former two and a reduction in the latter under environmental stress. This indicates a clear pectin solubilization in cherry tomato fruit. The enzymes pectolytic polyglacturonase (PG), pectin methylesterase (PME), and pectate lyase (PEL), altered their activities during the third sampling, while the calcium concentration fell drastically. Therefore, both the increase in pectin solubilization as well as the reduction in the Ca concentration during harshest environmental stress in the third sampling, especially in the parral greenhouse, could degenerate the textural properties of the cherry tomato, reducing its quality and consumer acceptance.     

Effects of a biocontrol agent of apple powdery mildew (Podosphaera leucotricha) on the host plant and on non-target organisms: an insect pest (Cydia pomonella) and a pathogen (Venturia inaequalis)

A number of studies have focused on the selection and use of new biocontrol agents, but the effects of the introduction of these microorganisms on non-target organisms, including the crop plants themselves, are not well known. Non-target effects of sprayed applications of a potential biocontrol agent of apple powdery mildew (Podosphaera leucotricha Ell. Et Ev.), on scab infections (Venturia inaequalis Cooke Winter), on codling moth [Cydia pomonella L. (Lepidoptera: Tortricidae)] oviposition and damage and apple (Malus x domestica) fruit quality are examined. This biocontrol agent, an epiphytic yeast isolate called Y16, affected neither conidia germination of V. inaequalis nor their penetration of the leaf tissue but suppressed the disease caused by this pathogen. The quantity of eggs laid by the codling moth during its second flight period on yeast treated trees was significantly different to the quantity of eggs laid on the untreated trees. In the first season of the experiments, more eggs were laid on the treated trees, especially on those tree parts closest to the fruit. These results, however, were not confirmed the following season: fewer eggs were laid on the treated trees than on the untreated trees. These conflicting observations are attributed to year-to-year variation in environmental conditions, which may affect yeast survival and activity. A 2-month-long assay was conducted in the orchard during the codling moth's second flight period from mid-July until mid-September. The yeast treatment did not affect the damage caused by the codling moth to the fruits. Finally, the yeast treatment did not affect any of the examined fruit quality parameters.     

Immediate alteration of Macrosiphum euphorbiae host plant-selection behaviour after biotic and abiotic damage inflicted to potato plants

The effects of potato [Solanum tuberosum L. (Solanaceae)] plant damage on the host plant-selection behaviour of the potato aphid, Macrosiphum euphorbiae Thomas (Homoptera: Aphididae), were studied. The damage inflicted to the plant was only of short duration and observations on aphid behaviour were made immediately following plant damage. The underlying questions of the study were to know how much time it takes for plant defence mechanisms to be activated and if this activation had noticeable repercussions on aphid behaviour. We considered stresses of various natures: biotic (pre-infestation by conspecifics or by Colorado potato beetles) and abiotic (scissor cuts). Aphid responses to host plant semiochemicals were investigated using a darkened arena bioassay and the probing behaviour was assessed using the electrical penetration graph technique. Aphids were attracted to their host plant (undamaged or damaged). In a preference test (undamaged plant vs. damaged plant), plants previously infested by conspecifics were preferred to undamaged plants, but this preference was not observed for heterospecific and abiotic damage. However, aphid probing behaviour was not modified on plants previously infested by conspecifics, whereas some changes were observed subsequently to heterospecific and abiotic damages. Our data present evidence that plants can respond to biotic and abiotic stresses soon after the damage is inflicted and when the damage is of short duration. The diverse consequences of these various local plant responses on M. euphorbiae behaviour are discussed in the context of plant defence strategies against aphid colonization.