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A morphological and quantitative characterization of early floral development in apple (Malus x domestica Borkh.).

Apple is an important crop and a focus of research worldwide. However, some aspects of floral commitment and morphogenesis remain unclear. A detailed characterization of bourse shoot apex development was undertaken to provide a framework for future genetic, molecular and physiological studies. Eight morphologically distinct stages of shoot apex development, prior to winter dormancy, were defined. Based on measurements of meristem diameter, two stages of vegetative development were recognized. Vegetative meristems were flat, and either narrow (stage 0) or broad (stage 1). Pronounced doming of the apex marked stage 2. During stage 3, the domed meristem initiated four to six lateral floral meristems and subtending bracts before converting to a terminal floral meristem (stage 4). The terminal floral meristem proceeded directly with bractlet and sepal initiation, while lateral floral meristems initiated bractlets (stage 5). Sepal initiation began on the basal lateral flower (stage 6) and continued in an acropetal direction until all floral meristems had completed sepal initiation (stage 7). In this study, only stage 0 and stage 7 apices were observed in dormant buds, indicating that stages 1-6 are transient. The results suggest that broadening of the apex (stage 1) is the first morphological sign of commitment to flowering.

Flowers↗

Winter bud content according to position in 3-year-old branching systems of 'Granny Smith' apple.

An investigation was made of the number of preformed organs in winter buds of 3-year-old reiterated complexes of the 'Granny Smith' cultivar. Winter bud content was studied with respect to bud position: terminal buds were compared on both long shoots and spurs according to branching order and shoot age, while axillary buds were compared between three zones (distal, median and proximal) along 1-year-old annual shoots in order 1. The percentage of winter buds that differentiated into inflorescences was determined and the flowers in each bud were counted for each bud category. The other organ categories considered were scales and leaf primordia. The results confirmed that a certain number of organs must be initiated before floral differentiation occurred. The minimum limit was estimated at about 15 organs on average, including scales. Total number of lateral organs formed was shown to vary with both bud position and meristem age, increasing from newly formed meristems to 1- and 2-year-old meristems on different shoot types. These differences in bud organogenesis depending on bud position, were consistent with the morphogenetic gradients observed in apple tree architecture. Axillary buds did not contain more than 15 organs on average and this low organogenetic activity of the meristems was related to a low number of flowers per bud. In contrast, the other bud categories contained more than 15 differentiated organs on average and a trade-off was observed between leaf and flower primordia. The ratio between the number of leaf and flower primordia per bud varied with shoot type. When the terminal buds on long shoots and spurs were compared, those on long shoots showed more flowers and a higher ratio of leaf to flower primordia.

Cell Differentiation↗

PEGASE: a machine language program for DNA sequence analysis on Apple II microcomputer using a binary coding of nucleotides.

The core of a 6502 machine language program for DNA sequence analysis on Apple II microcomputer is described. Use of a binary coding of nucleotides allows interactive data manipulation on a low-cost configuration with execution times similar to those of larger computers. The PEGASE system should prove useful and easy to use in routine sequence handling and experiment design.

Algorithms↗

Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data.

CAIC is an application for the Apple Macintosh which allows the valid analysis of comparative (multi-species) data sets that include continuous variables. Comparison among species is the most common technique for testing hypotheses of how organisms are adapted to their environments, but standard statistical tests like regression should not be used with species data. Such tests assume independence of data points, but related species often share traits by common descent rather than through independent adaptation. CAIC uses a phylogeny of the species in the data set to partition the variance among species into independent comparisons (technically, linear contrasts), each comparison being made at a different node in the phylogeny. There are two partitioning procedures--one used when all variables are continuous, the other when one variable is discrete. The resulting comparisons can be analysed validly in standard statistical packages to test hypotheses about correlated evolution among traits, to estimate parameters such as allometric exponents, and to compare rates of evolution. Previous versions of the package have already been used widely; this version is simpler to use and works on a wider range of machines. The package and manual are freely available by anonymous ftp or from the authors.

Data Interpretation, Statistical↗

PROTEUS: a suite of programs for prediction of structural features of proteins using an Apple IIe.

We have implemented several algorithms, developed by various authors for predicting structural features of proteins from their primary structure, on an Apple IIe and collected them in a suite, named PROTEUS. This suite incorporates: (i) methods for predicting secondary structure; (ii) the algorithm for computing the hydropathy profile using one out of five available sets of parameters; (iii) the algorithms for calculating the hydrophobic moment plot; and (iv) for performing the amphipathic analysis using one out of four available sets of parameters. The suite has a utility program for storing on a disk the sequence to be analysed. As an example, we applied some of the methods included in PROTEUS to predict the structure of a mitochondrial leader peptide. The results suggest the occurrence of structural features possibly related to the import of proteins into mitochondria.

Algorithms↗

An improved sequence handling package that runs on the Apple Macintosh.

We report improvements to our sequence analysis package and adaptation to run on the Apple Macintosh range of machines. The 'standard' version of the programs, which run on a VAX, has been given a new user interface that makes the programs very much easier to work with and has facilitated the move to the Macintosh. The reorganization of the code should simplify moves to other systems that offer WIMP user interfaces. In addition to a large number of small but useful extra features, some important new analytical functions have been devised. These include sequence and contig editors; optimal alignment and comparison methods; and a new method for comparing the observed and expected frequencies of selected oligonucleotides.

Base Sequence↗

MacT: Apple Macintosh programs for constructing phylogenetic trees.

MacT is a set of programs for the Apple Macintosh to construct and evaluate unrooted trees derived from amino acid sequences using a distance matrix method. Programs are designed on a 'one program--one task' basis for (i) determining the branching order in trees consisting of four or five species and calculating various statistical measures, (ii) calculating statistical measures for all possible topologies of unrooted trees and (iii) generating and evaluating trees derived from bootstrapped samples. With four auxiliary programs unrooted trees can be built for maximal 26 species, and the robustness of topologies be tested by bootstrapping.

Algorithms↗

MacP12: a protein property multi-profile plot program for the Apple Macintosh.

MacP12, a program for the Apple Macintosh, allows simultaneous plotting of two protein property profiles selectable from 12 built-in amino acid property scales. Various parameters such as the region to be analyzed, the size of the sliding window, the weighting function and the size of the graphical output can be easily adjusted by the user, which makes this program appropriate for diverse research questions. Since built-in scales can be simply exchanged, MacP12 is adaptable to the specific needs of the individual user.

Computer Graphics↗

A cluster of four receptor-like genes resides in the Vf locus that confers resistance to apple scab disease.

The Vf locus, derived from the crabapple species Malus floribunda 821, confers resistance to five races of the fungal pathogen Venturia inaequalis, the causal agent of apple scab disease. In our previous research, the Vf locus was restricted to a BAC contig of approximately 290 kb covered by five overlapping BAC clones. Here, we report on cloning of the resistance gene(s) present in the Vf BAC contig using a highly reliable and straightforward approach. This approach relies on hybridization of labeled cDNAs to amplified inserts of subclones derived from BAC inserts, followed by recovery of full-size transcripts by rapid amplification of cDNA ends (RACE). A cluster of four resistance paralogs (Vfa1, Vfa2, Vfa3, and Vfa4) was identified in the Vf locus. Vfa1, Vfa2 and Vfa4 had no introns and are predicted to encode proteins characterized with extracellular leucine-rich repeats (LRRs) and transmembrane (TM) domains. However, Vfa3 contains an insertion of 780 bp at the end of the LRR motif, resulting in multiple truncated transcripts. Comparison of Vfa1, Vfa2, and Vfa4 paralogs revealed a high degree of overall homology in their deduced amino acid sequences, while divergences were mainly restricted within LRR domains, including variable LRR units, numerous amino acid substitutions, and several residue deletions/duplications. Differential expression profiles among the four paralogs were observed during leaf development. Vfa1, Vfa2, and Vfa3 were active in immature leaves, but slightly expressed in mature leaves, while Vfa4 was active in immature leaves and was highly expressed in mature leaves.

Amino Acid Sequence↗

3 using odor-baited trap trees as sentinels to monitor plum curculio (Coleoptera: Curculionidae) in apple orchards.

In commercial orchards in Massachusetts in 2003, we conducted experiments aimed at developing guidelines for use of perimeter-row trap trees baited with grandisoic acid plus benzaldehyde as sentinels in a practical approach to determining need and timing of insecticide applications against overwintered plum curculios, Conotrachelus nenuphar (Herbst). Evaluations were based on percentages of sampled fruit injured by plum curculio. Trap trees baited with grandisoic acid released at approximately 1 mg/d plus benzaldehyde released at approximately 40 mg/d performed as well as or better than trap trees baited with greater or lesser amounts of these attractants in combination. The distance over which a trap tree baited with such odor was effective in aggregating damage to fruit extended to at least 31-33 m (maximum evaluated) along a perimeter row. Trap trees at corners of orchard blocks were as effective as perimeter-row trap trees midway between corner trees. Within the canopy of a trap tree, damage did not tend significantly to be localized in the vicinity of the odor source but tended to be rather evenly distributed among various sectors of the canopy. Finally, among three candidate thresholds evaluated as a trigger for insecticide application, a threshold of one freshly injured fruit proved better than thresholds of two or four freshly injured fruit out of 50 fruit sampled on a trap tree in assuring that orchard-wide damage would remain below a preset economic injury level of 1%. Our findings lead us to suggest that after a whole-orchard application of insecticide to apple trees in Massachusetts orchards shortly after petal fall, subsequent applications of insecticide against plum curculio can be confined to peripheral-row trees and be driven by a provisional threshold of one freshly injured fruit out of 50 fruit sampled on a perimeter-row trap tree baited with the above-mentioned odor.

Animals↗

Comparison of efficacy of programs using insecticide and insecticide plus mating disruption for controlling the obliquebanded leafroller in apple (Lepidoptera: Tortricidae).

The relative efficacy of an insecticide program and an insecticide plus mating disruption program using a sprayable pheromone formulation or a hand-applied pheromone dispenser was compared for control of the obliquebanded leafroller, Choristoneura rosaceana (Harris) at three commercial apple farms in a production area along the north shore of Lake Ontario, Canada, during 2000, 2001, and 2002. The average rate of disruption ranged from 50 to 80% in blocks of orchard treated with sprayable pheromone and from 84 to 98% in blocks treated with the hand-applied dispenser. The average proportion of shoots with larval feeding injury ranged from 0.002 to 0.09, 0.001 to 0.09, and 0.005 to 0.13 in the insecticide, insecticide plus sprayable pheromone, and insecticide plus hand-applied dispenser treatments, respectively, during the 3-yr study. The percentage of fruit with damage caused by spring, summer and overwintering larvae ranged from 0.03 to 0.06, 0.01 to 0.02, and 0.01 to 0.03 in the insecticide, insecticide plus sprayable pheromone, and insecticide plus hand-applied dispenser treatments, respectively. The addition of sex pheromone-mediated mating disruption to a conventional, insecticide-based program did not provide additional control of C. rosaceana feeding injury to shoots or fruit. The possible reasons for the failure of mating disruption to provide additional control are discussed.

Animals↗

Effects of ground cover treatments and insecticide use on population density and damage caused by Lygus lineolaris (Heteroptera: Miridae) in apple orchards.

We conducted a 2-yr study in commercial apple orchards in Nova Scotia to assess the effects of ground cover treatments and insecticides on population density and fruit injury caused by tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). The design was a split-plot with insecticides applied to whole orchard blocks and ground cover treatments applied to plots nested within orchard blocks. Ground cover treatments were 1) standard herbicide use, 2) enhanced weed control in tree rows, and 3) treatment two plus use of a selective herbicide in laneways. Treatments had few significant effects on vegetation in the tree row, but in laneways, known dicot hosts of L. lineolaris were suppressed and nonhost grasses promoted with treatment 3. Ground cover treatments did not affect cumulative captures of adult tarnished plant bugs on white sticky traps located in the plots but did affect captures in sweep nets. Split-plot ANOVA indicated no significant effect of insecticides on injury in either year, but ground cover treatments were significant in 2001. The lowest ranking rates of injury in both years were in orchards treated before bloom with a pyrethroid insecticide, either cyhalothrin-lambda or cypermethrin. The highest ranking rate of injury occurred in an orchard where insecticide was not applied until after bloom despite a high prebloom capture of L. lineolaris adults on orchard perimeter sticky traps. Fruit injury values for the ground cover treatment 3 were 63.3% (n.s.) and 50.0% (P < 0.05), respectively, of those in the standard treatment in 2000 and 2001.

Animals↗

Oriental fruit moth (Lepidoptera: Tortricidae) phenology and management with methoxyfenozide in North Carolina apples.

The phenology of oriental fruit moth, Grapholita molesta (Busck), on apple (Malus spp.) in North Carolina was studied using pheromone traps and egg sampling in abandoned and commercial orchards in 2000 and 2001, with subsequent development of an oviposition degree-day model and management studies in relation to codling moth, Cydia pomonella (L.), phenology. Oriental fruit moth eggs were found in greater numbers on leaves early and on fruit later in the growing season, on the top versus the bottom of the leaf surface, and on the calyx area versus the side or stem end of the fruit. A degree-day (DD) model to predict oriental fruit moth oviposition was developed based on temperature accumulations from peak moth trap capture of the first (overwintering) generation, by using 7.2 and 32.2 degrees C as the temperature limits. The model predicted four ovipositing generations of oriental fruit moth with the second beginning 507 DD after peak moth catch. Using predictions of the oriental fruit moth and codling moth degree-day oviposition models, an experiment was conducted to determine the level of second generation oriental fruit moth control with methoxyfenozide applied under different scenarios for first generation codling moth. Methoxyfenozide was equally effective in managing codling moth and oriental fruit moth for all treatment timings.

Animals↗

Phenology of Lacanobia subjuncta (Lepidoptera: Noctuidae) in Washington and Oregon apple orchards.

The phenology of Lacanobia subjuncta (Grote & Robinson) (Lepidoptera: Noctuidae) was investigated in 30 apple orchards in central Washington state and northeastern Oregon from 1998 to 2001 (57 total orchard-yr). Adult captures in pheromone-baited traps were fit to a Weibull distribution to model emergence of the first and second generations. Initial capture of first generation adults was observed at 216.2 +/- 2.6 degree-days (DD) (mean +/- SEM) from 1 March by using a base temperature of 6.7 degrees C. The model predicted that flight was 5 and 95% complete by 240 and 700 degree-days (DD), respectively. Monitoring of oviposition and hatch was used to establish a protandry plus preoviposition degree-day requirement of 160.0 +/- 7.7 DD, as well as to provide data to describe the entire hatch period. Egg hatch was 5 and 95% complete by 395 and 630 DD, respectively. The start of the second flight was observed at 1217.1 +/- 8.3 DD by using an upper threshold for development of 32 degrees C and a horizontal cutoff. The model indicated that the second flight was 5 and 95% complete by 1220 and 1690 DD, respectively. Second generation hatch was 5 and 95% complete by 1440 and 1740 DD, respectively. A discussion of the potential uses of these detailed phenology data in optimizing management strategies is presented.

Agriculture↗

Abscisic acid-specific binding sites in the flesh of developing apple fruit.

Abscisic acid (ABA) specific-binding sites localized in the cytosol were identified and characterized in the flesh of developing apple (Malus pumila L. cv. Starkrimon) fruit. ABA binding activity was scarcely detectable in the microsomes but high ABA binding activity in the cytosolic fraction was detected. The ABA-binding sites possessed a protein nature with both active serine residues and thiol-groups of cysteine residues in their functional binding sites. ABA binding was shown to be saturable, reversible and of high affinity. A Scatchard plot provided evidence for two different ABA binding proteins, one with higher affinity (K(d)=2.3 nM) and the other with lower affinity (K(d)=58.8 nM). Phaseic acid, trans-ABA and (-)-ABA had essentially no affinity for the binding proteins, indicating their stereo-specificity to bind physiologically active cis-(+)-ABA. The time-course, pH- and temperature-dependence of the ABA-binding proteins were determined. It is hypothesized that the detected ABA-binding proteins may be putative ABA-receptors that mediate ABA signals during fruit development.

Abscisic Acid↗

Role of neonicotinyl insecticides in Washington apple integrated pest management. Part II. Nontarget effects on integrated mite control.

The effect of neonicotinyl insecticides on integrated mite control in Washington apple was examined from 0 In a series of 20 field trials (54 treatments) designed primarily to look at efficacy against the codling moth, Cydia pomonella, nearly half of the treatments using four or more applications of acetamiprid had peak mite densities exceeding the economic threshold of 5 mites per leaf. Overall, acetamiprid treatments had 4.6-fold higher mite densities than the standard organophosphate insecticide treatment. Of the treatments with high mite populations, Panonychus ulmi, the European red mite, and Tetranychus urticae, the twospotted spider mite, were the dominant species in roughly equal numbers of cases. Only 11.1% of the thiacloprid treatments exceeded 5 mites per leaf; these experimental treatments included eight applications, whereas the current label restricts the number of applications at the rate for C. pomonella to two applications. One out of six clothianidin treatments caused a significantly higher mite density than the standard treatment; however, this material appeared to suppress predatory mites. Neonicotinyl insecticides did not eliminate predatory mites, but they inhibited their ability to respond normally to increasing prey populations. In field trials designed specifically to examine mite population densities where neonicotinyl insecticides were used, significantly higher levels of tetranychid mites occurred in one or more acetamiprid treatments (one, two or four applications) in five out of six trials. In the sixth trial (in a commercial orchard), only two acetamiprid applications were made, and mite populations were low in all treatments. While elevated mite densities were more likely to occur with four applications, in one case it occurred following a single application. The predominant tetranychid mite species (either P. ulmi or T. urticae) varied from trial to trial; however, there was no apparent bias regarding stimulation of the two species. Horticultural mineral oil was used with acetamiprid in some trials in an attempt to mitigate mite outbreaks. However, the addition of oil did not counteract the tendency of acetamiprid to increase tetranychid mite populations, and in one trial, had a negative effect on predatory mite densities. Seasonal tetranychid mite density was positively related to the total grams AI (or number of applications) of acetamiprid, thus reducing the number of applications per season should lower the probability of mite outbreaks.

Anabasine↗

KNAP2, a class I KN1-like gene is a negative marker of bud growth potential in apple trees (Malus domestica [L.] Borkh.).

The determinism of bud bursting pattern along the 1-year-old shoot was studied at the molecular and morphological levels in the apple tree variety 'Lodi' which shows an acrotonic tendency. At the molecular level, the expression of KNAP2, which belongs to the class I KN1-like gene family, was studied. Measurements were carried out during dormancy (October), breaking dormancy (January) and just before bud bursting (March). The results showed that KNAP2 is more highly expressed in buds that will remain at rest in the spring. Expression of KNAP2 was found in the meristem and in the marginal meristem of the two latest shaped primordia. In the January and March buds, this gene is also expressed in the procambial zone underneath the apical meristem. This study therefore suggests that KNAP2 may be considered as a negative marker of bud growth potential and that the growth inhibition in proximal buds could partially result from differential gene activity. At the morphological level, it was shown that no organogenetic activity took place between October and March as revealed by the constant number of leaf primordia in buds. Nevertheless, those buds likely to grow the following spring had a larger size and fewer hard scales than other buds. This suggests that genetic control may act together with other mechanisms, possibly physical (number of scales) or biochemical, to control bud inhibition.

Base Sequence↗

Xanthophyll cycle pool size and composition in relation to the nitrogen content of apple leaves.

The objective of this study was to determine xanthophyll cycle pool size and composition in response to N status and their relationships to non-photochemical quenching in apple leaves. Bench-grafted Fuji/M.26 trees were fertilized with different N concentrations (0-20 mM) in a modified Hoagland's solution for 6 weeks to create a wide range of leaf N status (1-4.4 g m(-2)). Chlorophyll content, xanthophyll cycle pool size, lutein, total carotene, and neoxanthin on a leaf area basis all increased linearly with increasing leaf N. However, only the ratios of the xanthophyll cycle pool and of lutein to chlorophyll were higher in low N leaves than in high N leaves. Under high light at midday, both zeaxanthin (Z), expressed on a chlorophyll basis, and the percentage of the xanthophyll cycle pool present as Z, increased as leaf N decreased. Thermal dissipation of excitation energy, measured as non-photochemical quenching of chlorophyll fluorescence, was positively related to, whereas efficiency of excitation transfer and photosystem II quantum efficiency were negatively related to, Z, expressed on a chlorophyll basis or on a xanthophyll cycle pool basis. It is concluded that both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to zeaxanthin are enhanced in response to N limitation to dissipate excessive absorbed light under high irradiance.

Chlorophyll↗