Susceptibility of selected apple cultivars to the Mediterranean fruit fly

Ceratitis capitata (Wiedemann), the Mediterranean fruit fly, is one of the key pest species affecting deciduous fruit orchards along the Mediterranean coasts. Because of global warming, C. capitata is gradually spreading north and is becoming a major pest of apples. Determining the susceptibility of the main apple varieties grown in the region will serve as a cornerstone to the management of this pest. In this study, we show the results of a field and laboratory no‐choice test conducted to determine the Medfly preferences on different apple cultivars. The seven main varieties of apples (Gala, Red Delicious, Golden Delicious, Granny Smith, Kanzi, Morgen Dallago and Fuji) were tested. The results demonstrate that C. capitata lays eggs on all apple cultivars in both field and laboratory conditions. The Granny Smith, Red Delicious and Morgen Dallago varieties showed the lowest susceptibility in laboratory conditions, (0.75, 1.55, 2 oviposition punctures/fruit, respectively), with significant differences in oviposition compared to the Golden Delicious, Kanzi and Fuji (3.27, 3.31, 3.1 oviposition punctures/fruit, respectively) varieties, which were shown to be the most susceptible to Medfly attack in laboratory conditions. On the other hand, only slight and not statistically significant differences emerged from the field trials. In relation to the physico‐chemical characteristics, the apple cultivars showing the lowest susceptibility (Granny Smith, Red Delicious and Morgen Dallago) had harder peels and pulps and lower sugar contents than the most susceptible cultivars (Golden Delicious, Fuji and Kanzi). These results were also confirmed through evaluation of larval development on different varieties. In fact, Granny Smith, Red Delicious and Morgen Dallago were the three varieties that did not allow adequate larval and adult development and reduced the possibility of the emergence of a new generation.     

Relationship of Endopolygalacturonase Inhibitor Activity to the Rate of Fungal Rot Development in Apple Fruits

An inhibitor extracted form the cell walls of apple fruits suppressed the activity of endopopygalacruronases (endo-PGs) produced in vivo and in vitro by Nectria galligena, Phomopsis mali, Fusarium Lateritium and Glomerella cingulata but not the endo-PGs produced by Penicillium expansum or Phytophtobora syringae. Of four apple cultivars tested Granny Smith tissue contained the highest levels of inhibitor and Cox's Orange Pippin contained the least. Linear rot expansion in the four apple cultivars inoculated with N. galligena was inversely related to inhibitor activity in the fruit tissue, rot development being slowest in Granny Smith fruits and most rapid in Cox's Orange Pippin fruits. Rot expansion in fruits inoculated with P. expansum bore no such relationship to inhibitor activity in the tissue Apple tissue maceration by the endo-PGs from N. galligena, P. mali. F. lateritium and G. cingulata was similarly related to inhibitory activity in the fruit. The properties of the partially purified inhibitor were consistent with it being proteinaceous but the relative slowness with which it was hear inactivated and the presence of a small percentage of carbohydrate might indicate that it was a glycoprotein.     

Laboratory tests carried out onMicrothrix inconspicuella [Lep.: Pyralidae], a biological control agent forEmex australis in Australia

Host specificity tests of the moth,Microthrix inconspicuella Ragonot in Australia, indicated that larvae could feed and develop on young apple leaves. Additional tests in South Africa on leaves and fruit of the 4 apple varieties, Jonathan, Starking (Red Delicious), Granny Smith and Golden Delicious, showed that apples were not a preferred food. Little feeding occurred and pupation happened infrequently. No 2^nd generation resulted whenM. inconspicuella colonies were confined on apple fruit or leaves.      

A test of fruit varieties on entry rate and development by neonate larvae of the codling moth,Cydia pomonella

The rate of entry by neonate larvae of the frugivorous codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), into fruit material was investigated. We used no‐choice bioassays in climate‐controlled rooms to assay larval entry across four host plant species (apple, pear, quince, walnut) and three varieties within a single fruit species (apple). Larvae successfully entering apples were reared to adulthood, and we collected tissue samples from apples which were successfully colonized in order to determine sucrose concentrations. This information was used to evaluate differences in adult moth size, development time, and pulp sucrose concentration due to apple variety. Four important findings emerged: (1) neonate larvae had the highest frequency of entry (86% of larvae) into apple fruits, compared with pear (78%), quince (56%), and walnut (32%); (2) the frequency of larval entry into immature apples differed across apple varieties, and larval entry rate was highest in variety Golden Delicious (72%), compared with Granny Smith (46%) and Red Delicious (64%); (3) on average, adult moths were larger and development times were shorter on the variety with the highest entry frequency (Golden Delicious); and (4) apple pulp sucrose concentrations were higher for Golden Delicious (17.5 μg mg^?1) than for either Granny Smith (15.9 μg mg^?1) or Red Delicious (15.1 μg mg^?1) varieties, which correlates positively with entry and development data. We conclude that host fruit species and varietals within a species affect the entry rate of neonate codling moth larvae in no‐choice assays. We hypothesize that larval development is influenced by mean sucrose concentrations or other phytochemical differences associated with host fruit varieties.     

Initiation of Rapid Ethylene Synthesis by Apple and Pear Fruits in Relation to Storage Temperature

The influence of storage temperature on the onset of rapid ethyleneproduction was investigated for fruits of Conference pear (Pyruscommunis L.) and five cultivars of apple (Malus domestica Borkh.).The time taken from harvest to rapid ethylene production wasshorter and more uniform at 3 ?C than at 18–20 ?C forConference pears and Golden Delicious apples. Increases in internalethylene concentration, 1-amino cyclopropane-1-carboxylic acidconcentration and ethylene production were simultaneous in GoldenDelicious apples at 3 ?C. When Golden Delicious apples wereheld at 3 ?C for 48 h and then kept at 20 ?C the mean time ofonset of ethylene production was similar to that for applesheld continuously at 20 ?C. However, two periods of 48 h at3 ?C caused earlier ethylene production. Conversely, ethyleneproduction at 3 ?C was delayed by transfer to 20 ?C for twoperiods of 48 h. Cox's Orange Pippin and other apple cultivarstended to show more synchronous ethylene production at 3 ?Cthan at higher temperatures but the mean time of onset was eitherunaffected by temperature or slighdy delayed at lower temperature.Acceleration of the onset of ethylene production by low temperaturewas never observed in Cox's Orange Pippin apples harvested atweekly intervals from 10 August to 17 September. Key words: Ethylene, Storage temperature, Pyrus communis, Malus domestica     

Factors affecting the presence of Typhlodromusspp. (Acarina: Phytoseiidae) in the calyx cavities of apple fruits and implications for integrated pest management

Predatory mites of the family Phytoseiidae include several species of importance as biological control agents of phytophagous mites in various crops including apples. We report on the post-harvest presence of the motiles of two species, Typhlodromus occidentalis and Typhlodromus pyri, in the calyx cavities of apple fruits of three cultivars. The mean numbers of motiles per fruit were as high as 6.10. The phytoseiid densities were lowest in cv. Bonza and tended to be greater in samples taken in late autumn, particularly in cv. Red Delicious. No significant effect (p > 0.05) was observed for different insecticide treatments. Phytoseiids remained present within fruits of cv. Granny Smith left on the orchard floor in winter. Together with an observed reduction in the numbers of T. occidentalis in the early spring, this suggests that fruits constitute an overwintering refuge. The findings are discussed in relation to the implications for biological control, in particular the minimization of the removal of natural enemies from orchards. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fungitoxic and phytotoxic effect of some surface-active agents applied for the control of apple powdery mildew

Mixtures of methyl esters of fatty acids (‘Off-Shoot O’) and mixtures of fatty alcohols (‘Off-Shoot T’), applied during the late autumn (November), eradicated apple powdery mildew (caused by Podosphaera leucotricha) from infected buds. Applications in the spring at bud-burst were less effective. The autumn sprays caused little damage to the cultivars Bramley's Seedling, Cox's Orange Pippin and Golden Delicious but on Worcester Pearmain 50% of the buds were killed by a 5% Off-Shoot O spray. The bud-burst sprays were damaging and reduced yield on the Cox and Bramley trees. A 5% a.i. mixture of nonanol/lissapol applied to a range of commercial cultivars was effective in eradicating powdery mildew but was more phytotoxic than the Off-Shoot compounds. Spraying Cox trees later in the winter failed to reduce the damage. Eradication of the overwintering stage of the disease resulted in low spore concentrations during the following spring and early summer, enabling some economies to be made in the summer mildew fungicide programme.     

Differential gene expression analysis of ‘Granny Smith’ apple (Malus domestica Borkh.) during fruit skin coloration

‘Granny Smith’ apples growing under normal sunlight develop green skin, whereas the peel turns red due to anthocyanin accumulation after the removal of a bagging treatment. Two anthocyanins, Cyanidin 3-O-galactoside (cy3-gal) and Cyanidin 3-O-arabinoside (cy3-ara), were detected in the red ‘Granny Smith’ apple peels, and cy3-gal was determined to be chiefly responsible for the red color. The content of cy3-gal was more than 98% of the total anthocyanin in the red ‘Granny Smith’ peels. To better understand the molecular basis of anthocyanin biosynthesis in ‘Granny Smith’ apples, we performed a quantitative real-time PCR (qRT-PCR) analysis of anthocyanin biosynthetic genes (MdCHS, MdF3H, MdDFR, MdANS, MdUFGT, and MdMYB1). Our results indicate that the expression of these genes (except MdCHS) was associated with increased anthocyanin accumulation in the skin of ‘Granny Smith’ apples. Four selected genes obtained from the ‘Granny Smith’ skin cDNA library, phytoene synthase (PSY), WD40 repeat protein, polygalacturonase (PG), and galactosidase (GAL), were also confirmed by qRT-PCR. We found that these genes were differently expressed during ‘Granny Smith’ apple skin coloration, suggesting that they are directly or indirectly involved in pigment accumulation. In conclusion, anthocyanin biosynthesis in ‘Granny Smith’ apples is the result of interactions between multiple enzymes in the anthocyanin biosynthesis pathway, and the coloring mechanism of ‘Granny Smith’ apples may be similar to that of red-skinned cultivars.     

The response of apples cv. Cox's Orange Pippin to different concentrations of oxygen in the storage atmosphere

The response of apples cv. Cox's Orange Pippin to storage in flowing streams of air and nitrogen mixed to generate atmospheres ranging from 0.5% to 2% oxygen was examined in two seasons. The benefits of reducing store oxygen concentrations below 1.25% were small but storage in 0.75% may be advantageous for Cox's Orange Pippin apples in seasons when flesh firmness is low at harvest. Ethanol-induced flesh breakdown was recorded in samples stored in 0.5% O₂ in one season and the risk of low temperature breakdown was increased in oxygen levels below 1.25%. Ethylene production was reduced by lowering the oxygen concentration.     

Hatching of the winter eggs of the fruit-tree red spider mite (Panonychus ulmi (Koch))

Observations on the hatching of winter eggs of Panonychus ulmi (Koch) from apple orchards in England over the 5 years 1962-6 are described. Differences of 2–3 weeks between orchards in the date at which 50% hatch was reached were quite common and this was out of step with petal fall in the majority of orchards. There was a continuous range between early and late hatching populations and a tendency for the populations to hatch in the same order every year. In 1966 populations on Cox's Orange Pippin hatched earlier than those on Worcester Pearmain but the difference was unlikely to be of practical importance. Neither recording accumulated day degrees for populations hatched out-of-doors nor hatching in an incubator after chilling was considered to give a sufficiently reliable forecast of 50% hatch but observations in 1966 suggested that this might be predicted from the total eggs hatched in an incubator expressed as a percentage of total healthy eggs.     

The Effect of Temperature on Growth and Mineral Nutrition of Fruits of Apple, with Special Reference to Calcium

Growth and mineral composition of fruits in potted trees were studied at two temperatures (19 and 24°C) in two experiments with Golden Delicious and one with Cox's Orange Pippin under a controlled environment. In Golden Delicious the high temperature promoted fruit growth markedly, but in Cox's Orange Pippin the stimulation was much less pronounced. The levels of K, N, Mg, and P (expressed as amounts per fruit) were increased at the higher temperature. This increase was almost completely the result of differences in fruit growth. With respect to Ca the high temperature reduced Ca influx in one Golden Delicious experiment and had hardly any effect in the other, but favoured influx in Cox's Orange Pippin. In one Golden Delicious experiment the temperature was raised 7 weeks after blossoming, which resulted in a temporary drop of Ca. When the same temperature change was applied 4 weeks earlier, Ca continued to increase. It is assumed that mineral influx occurs via the xylem during the first few weeks after fruit set and via the phloem throughout. The results are discussed in terms of differences in mobility in the phloem for the various minerals and of a shift in the ratio between xylem and phloem movement induced by differences in the growth rate of the fruits.     

The use of heat to control the rotting of Cox's Orange Pippin apples by Gloeosporium spp

Dipping in warm water successfully reduced the incidence of infection of Cox's Orange Pippin apples by Gloeosporium spp. Treatment of fruit loaded after harvest with spores of G. perennans was most successful if carried out 3–9 days after inoculation; later treatment was less effective. Infection taking place late in the growing season was relatively more susceptible to treatment than infections established on less mature fruit. Steam/air mixtures provided a successful, alternative source of heat; accelerated cooling after treatment with such mixtures did not reduce their effect. Browning of the skin and increased incidence of rotting by Penicillium spp. may follow heat treatment. With liquid cultures heat has a greater effect on germinated than on ungerminated spores and over the range of temperatures used for treating apples results in delayed fungal development rather than eradication.     

Post-harvest chemical treatments for the control of storage disorders of apples

Immersion of apples of the varieties Cox's Orange Pippin and James Grieve for 1 min in solutions of calcium chloride or nitrate reduced the incidence of bitter pit and senescent breakdown that developed during air storage at 3 °C. Calcium nitrate treatments decreased the severity of superficial scald in both Bramley's Seedling and Cox apples probably by slightly delaying the rate of senescence. Calcium chloride caused unacceptable levels of damage when applied to Cox and Grieve at concentrations above 0.125 M; this injury was enhanced in Cox when benomyl was added to this strength of solution. Bramley's Seedling apples were more sensitive to calcium injury than Cox, especially in the presence of benomyl and the scald inhibitor, ethoxyquin; diphenylamine did not increase calcium injury. Calcium nitrate caused more damage to Cox than equimolar concentrations of the chloride without improving the control of bitter pit. Virtually no damage occurred when Cox and Grieve apples were immersed for 10 min in 0.125 M calcium nitrate at 45 °C. The incorporation of calcium in warm water treatments to control rotting and scald may delay sensecent breakdown in heat-treated apples.     

An investigation of persistent infection of stored apples by Gloeosporium spp.

Orchards of Cox's Orange Pippin apples with a history of persistent Gloeosporium infection were examined for wood infections and fruit susceptibility. The amount of wood infection on the trees was not excessively high and the conidia from wood and fruit infections were not resistant to captan. Extensive rotting developed following the application of conidia of G. perennans to the surface of the fruit after harvest. Mineral analysis indicated low calcium and high nitrogen content and it is suggested that fruit susceptibility associated with mineral imbalance is responsible for much of the rotting encountered in the past.     

Epistatic fire blight resistance QTL alleles in the apple cultivar ‘Enterprise’ and selection X-6398 discovered and characterized through pedigree-informed analysis

Most cultivated apple cultivars are highly susceptible to fire blight, caused by Erwinia amylovora. However, differences in resistance levels are observed among cultivars and could be used in breeding. In this paper, we investigated the genetic basis of fire blight resistance of the cultivar ‘Enterprise’ and the advanced breeding selection X-6398. Genotyped pedigrees were used for validating and curating historic pedigree records. Various quantitative trait locus (QTL) discovery approaches were applied on the full-sib families ‘Gala’ × ‘Enterprise’ (GaEn) and X-6398 × X-6683 (IW) with the software FlexQTL? and MapQTL®. The paternal lineage of ‘Enterprise’ was reconstructed and showed to include ‘Cox’s Orange Pippin’. The QTLs found varied with the software used. Using FlexQTL?, two were found on linkage groups (LGs) 7 and 13, favourable alleles inherited by Enterprise from ‘Cox’s Orange Pippin’ and ‘Golden Delicious’, respectively. The former was identical to the previously named FB_F7 allele from ‘Fiesta’, while the latter is new and has been named FB_13GD. X-6398 had a QTL at the same position as FB_F7. Its favourable allele was new, originating from the unknown grandfather of X-4598, and was named FB_7X-6398. Using MapQTL® on GaEn, FB_F7 was also identified. Performing the same analysis on the subset of offspring that carried the favourable allele of FB_F7, two putative QTLs on LG8 and on top of LG13 were identified, which showed interactions with FB_F7. Implication of the findings for breeding for fire blight-resistant apples is discussed. Single nucleotide polymorphism data on Enterprise and its ancestors are provided.     

Demography and mass-rearing of Carposina sasakii Matsumura (Lepidoptera: Carposinidae) reared on Golden Delicious and Red Fuji apples in the laboratory

Carposina sasakii Matsumura (Lepidoptera: Carposinidae), is one of the most serious fruit-boring pests in over ten species of fruit trees, and is especially damaging apples in the northern of China. The application of new planting systems, i.e., high-density and dwarfing rootstock orchard systems with mixed apple varieties, makes it important to study the fitness of C. sasakii on these apple varieties to gain fundamental knowledge for use in pest management involving this insect. In this study, life table data of C. sasakii were collected using Golden Delicious and Red Fuji apples as hosts. The egg-larva duration of male C. sasakii reared on Golden Delicious apples (22.81 d) was significantly shorter than that reared on Red Fuji apples (24.27 d). The egg-larva mortality in Golden Delicious apples (59.00%) was lower than that in Red Fuji apples (72.49%). The mortality of the pupal stage, however, was higher in Golden Delicious (10.51%) than in Red Fuji (0%). The total oviposition period (TPOP) on Golden Delicious apples (32.94 d) was significantly shorter than in individuals reared on Red Fuji apples (34.19 d). The intrinsic rate of increase (r = 0.0581 d⁻¹), net reproductive rate (R₀ = 7.57 offspring), and finite rate of increase (λ = 1.0598 d⁻¹) were all higher on Golden Delicious than those on Red Fuji. When the net reproductive rate (R₀) was used, the harvest rate of pupae was higher (0.8678) when reared on Golden Delicious apples than when reared on Red Fuji apples (0.8398). When a large cohort size (n = 200) was used for effective bootstrap sample, the P_E values for C. sasakii reared on Golden Delicious apples and Red Fuji apples were both almost equal to 1. For C. sasakii culturing purposes, Golden Delicious apples would be more productive than Red Fuji.     

The ultrastructure of the outer tissues of cold-stored apple fruits of high and low calcium content in relation to cell breakdown

The outer tissues of Cox's Orange Pippin apples from samples with initially high and low calcium content were examined in the electron microscope following 53, 81 or 99 days in air storage at 3 ^oC. Cell ultrastructure within tissues of both high and low calcium apples was comparatively normal in fruit stored for the shorter period but low calcium fruit showed symptoms of membrane breakdown after 81 days. The greatest structural differences were observed after storage for 99 days when low calcium fruits contained more cells exhibiting breakdown of membranes and organelles than high calcium apples and also showed more severe symptoms of cell wall breakdown.     

Integrated control of apple pests in New Zealand

In a study at Appleby Research Orchard, Nelson, examination of the fruit from mature ‘Delicious’ apple trees sprayed with ryania over 5 years showed that less than 10% of 5th‐instar larvae of the codling moth (Laspeyresia pomonella) seeking cocooning sites originated from fruit on the ground. In 1972 and 1973 the survival of such larvae was studied by tagging with cobalt‐58 and releasing them beneath mature trees. In both years about 25 % of the tagged larvae returned to the tree to spin cocoons. Larvae released on bare ground 0–1 m from the tree trunks were more successful than those released in the sward 1–2 m away. Once on the trees, most larvae spun cocoons beneath exfoliating bark on the lower parts of the leaders and the trunk. Fifty‐two percent of the cocoons located were formed on the ground, and overwintering mortality of these was estimated to be near 100%. The pre‐cocooning mortality of larvae released on the ground was similar to that of larvae released on the trees in the same year. It was concluded that larvae from windfalls could be ignored in estimating 5th‐instar larval mortality of codling moth on ‘Delicious’ trees. On the cultivars ‘Dunn's Favourite’ and ‘Cox's Orange Pippin’, however, the higher percentage of larvae in windfalls made their inclusion in mortality estimates essential.     

Integrated control of apple pests in New Zealand 6. Incidence of European red mite,Panonychus ulmi (Koch), and its predators

Mite relationships were investigated in an orchard near Nelson from 1962 to 1974 in conjunction with a long‐term experiment into integrated control of apple pests. From 42% to 57% of the total winter eggs of Panonychus ulmi hatched over a period of 48–53 days from the last week of September until mid November. The main hatch—from 10% to 90%—took 19–20 days. Five generations occurred in each season, from October to March, although some females laid winter eggs from mid January if leaf condition became poor. Insect predators found were Stethorus bifidus, Sejanus albisignata, Arthrocnodax sp., and Xylapothrips sp. The mite Typhlodromus pyri (Phytoseiidae), the most important predator, had up to 5 generations from October to March; some females ceased to feed or oviposit from mid February onwards, and took on the characteristics of the overwintering diapause phase. With the integrated programme based on ryania, a favourable balance of P. ulmi and T. pyri was established after an initial outbreak of P. ulmi in the 1st or 2nd season, and was maintained until 1970–71, when P. ulmi outbreaks occurred on several cultivars in a season marked by hot, dry conditions in November and December. Natural control was restored the next year except on cy. Delicious, where P. ulmi remained in greater numbers for several years. With a complete commercial spray programme from 1962 to 1967 P. ulmi became resistant to all acaricides used; with the regular azinphos‐methyl programme and no acaricides in 1967–68 a population of T. pyri resistant to this insecticide emerged. The approximately × 10 resistance level did not increase appreciably, so the azinphos‐methyl dosage was reduced from 0.05% to 0.025% to allow greater survival. Several hot, dry summers followed, and commercial control of P. ulmi by T. pyri did not occur until 1973–74. A programme of low‐dosage carbaryl allowed T. pyri and S. albisignata to establish in fair numbers, but control of P. ulmi was not achieved. Experiments with mineral oils and cyhexatin have shown them to have some potential for inclusion against P. ulmi in future integrated programmes.     

Electron-energy-loss spectroscopic imaging of calcium and nitrogen in the cell walls of apple fruits

Changes in texture are an integral part of ripening in most fleshy fruits and these changes are thought to be determined, primarily, by alterations in cell wall structure. Electron energy loss spectroscopy (EELS) imaging was used to obtain quantitative information on the levels of calcium and nitrogen in the cell walls of apple (Malus domestica Borkh. cv. Cox's Orange Pippin) fruits. Samples of fruit cortex were prepared for EELS by high-pressure freezing and molecular distillation drying to minimize loss and redistribution of soluble cell wall components such as calcium. The EELS imaging successfully resolved calcium and nitrogen levels in the middle lamella and primary cell wall. When the elemental compositions of the cell walls of Cox's apples from two sites in the UK were compared at harvest or after 6 months storage, the orchard which always produced consistently firmer fruit had significantly lower levels of cell wall calcium and higher levels of cell wall nitrogen. This result was unexpected since firm texture in apples and other fruits has been commonly associated with elevated levels of fruit calcium. The nitrogen-rich material in the sections used for EELS was insoluble in acidified methanol, indicating that it represented a high-molecular-weight component in the cell wall. Furthermore, total tissue hydroxyproline levels were greatest in material with elevated cell wall nitrogen, suggesting enhanced levels of wall structural proteins in the tissue. These data indicate a correlation between increased amounts of cell wall nitrogen and firm fruit texture. The possible role of cell wall proteins in determining the textural properties of fruit tissue is discussed. Received: 19 November 1998 / Accepted: 28 January 1999