Differences In Fruit Size Research Articles

Genotypic Differences in Sweet Cherry Fruit Size are Primarily a Function of Cell Number

Understanding the genetic control of fruit size in sweet cherry (Prunus avium L.) is critical for maximizing fruit size and profitable fresh market production. In cherry, coordinated cycles of cell division and expansion of the carpel result in a fleshy mesocarp that adheres to a stony endocarp. How these structural changes are influenced by differing genetics and environments to result in differing fruit sizes is not known. Thus, the authors measured mesocarp cell length and cell number as components of fruit size. To determine the relative genotypic contribution, five sweet cherry cultivars ranging from ≈1 to 13 g fresh weight were evaluated. To determine the relative environmental contribution to fruit size, different-size fruit within the same genotype and from the same genotype grown in different environments were evaluated. Mesocarp cell number was the major contributor to the differences in fruit equatorial diameter among the five sweet cherry cultivars. The cultivars fell into three significantly different cell number classes: ≈28 cells, ≈45 cells, and ≈78 cells per radial mesocarp section. Furthermore, mesocarp cell number was remarkably stable and virtually unaffected by the environment as neither growing location nor physiological factors that reduced final fruit size significantly altered the cell numbers. Cell length was also significantly different among the cultivars, but failed to contribute to the overall difference in fruit size. Cell length was significantly influenced by the environment, indicating that cultural practices that maximize mesocarp cell size should be used to achieve a cultivar's fruit size potential.

Biologically Active Gibberellins and Abscisic Acid in Fruit of Two Late-maturing Japanese Pear Cultivars with Contrasting Fruit Size

Both ‘Atago’ and ‘Shinkou’ are late-season japanese pear (Pyrus pyrifolia Nakai) cultivars with russet-brown fruit, and the progenies of crosses made between ‘Nijisseiki’ and unknown cultivars, but they display different growth habit, fruit size, and fruit quality. To clarify the difference in fruit development between the two cultivars, the levels of endogenous gibberellins (GA1, GA3, and GA4) and abscisic acid (ABA) in fruit were identified and quantified by gas chromatography/mass spectrometry, and a histological study of fruit was carried out. The results showed that cell number rather than cell size of mesocarp is responsible for the difference in fruit size between the two cultivars. Furthermore, analysis of endogenous bioactive gibberellins revealed that ‘Atago’ fruit has much higher levels of GA1, GA3, and GA4 than ‘Shinkou’ fruit during fruit development, particularly during the early period of fruit growth. However, ‘Shinkou’ has a much higher ABA level than ‘Atago’ during the early period of fruit development. Abscisic acid concentration remained at an extremely low level after the first production peak after anthesis in ‘Atago’ compared with ‘Shinkou’.

GROWTH AND FRUITING CHARACTERISTICS OF EIGHT APPLE GENOTYPES ASSESSED AS UNPRUNED TREES ON 'M.9' ROOTSTOCK AND AS OWN-ROOTED TREES IN SOUTHERN FRANCE

ISHS VIII International Symposium on Canopy, Rootstocks and Environmental Physiology in Orchard Systems GROWTH AND FRUITING CHARACTERISTICS OF EIGHT APPLE GENOTYPES ASSESSED AS UNPRUNED TREES ON 'M.9' ROOTSTOCK AND AS OWN-ROOTED TREES IN SOUTHERN FRANCE

Crop load expressed in terms of intercepted photosynthetically-active radiation can be used as a covariate to compare peach tree performance

SummaryWhen fruit tree performance is evaluated in rootstock, thinning or other management trials, tree size and fruit number (or crop load) are the most important factors that confound the real effects of the treatments that are being evaluated. An experiment to assess the effects of tree size and crop load on yield efficiency and fruit size was conducted in a ‘Ross’ peach orchard on ‘Nemaguard’ rootstock in Malloa, Chile. Two groups of 15 trees each were selected according to tree size and were hand-thinned at the beginning of pit hardening to a wide range of crop loads within each tree size group, but keeping the average crop load similar between the two groups of trees. Fruits per tree (crop load) was either normalised or not normalised for tree size, assessed either as cm–2 of trunk cross-sectional area (TCSA) or the fraction of above-canopy photosynthetically-active radiation (PARf) intercepted by the canopy at harvest. At harvest, all the fruits were counted and weighed, and the average fruit weight calculated. Analysis of variance and covariance (with and without using crop load as a covariate), and regression analysis were performed and the results were compared. Differences in fruit size, yield efficiency (yield normalised by tree size) and total production between the two tree size groups were detected by ANOVA; but, by selecting the appropriate covariate, no differences between groups were detected. Thus, for a correct interpretation of the effect of treatment, in this case tree size, on tree performance measured as fruit size, yield, or yield efficiency, the differences in crop load (number of fruits per tree) must be removed by performing covariance analysis. Normalising crop load (fruits per tree) to account for tree size was essential for proper interpretation of the data. Calculating crop load using the fraction of light intercepted at harvest as the normalising factor was better than using TCSA as the normalising factor.

(214) Adult Pear Response to Integrated Nitrogen Fertigation and Drip Irrigation System

Responses of adult pear to the integrated N fertigation and drip irrigation system have not been documented in Oregon. A field trial was conducted on adult pear at the Mid-Columbia Agricultural Research and Extension Center, Hood River, Ore., in 2005. Two N and water management systems (integrated N fertigation and drip irrigation system; and broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system) were compared on pear cultivars of Bartlett and Golden Russet Bosc, and rootstocks of OH×F97 and OH×F87. The responses of these cultivars and rootstocks to the integrated N fertigation and drip irrigation system were similar. The integrated N fertigation and drip irrigation system consumed 1450 m3·ha-1 of irrigation water during the entire season from May to September, reducing irrigation water use by 73% compared with 5297 m3·ha-1 under the current system—broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system averaged over the four cultivar and rootstock combinations. The fruit yield was statistically similar for the integrated N fertigation and drip irrigation system and the broadcast application of dry N fertilizer and microsprinkler irrigation system on the average of the four cultivars and rootstocks. Differences in fruit size and color were negligible between the two N and irrigation management systems. Overall, our results suggest that adopting the integrated N fertigation and drip irrigation system does not cause significant reduction in yield or quality of adult pear; the integrated N fertigation and drip irrigation system could be a profitable and environmentally sound management alternative for pear production.

(21) Using Compost Sources as an Alternative to Methyl Bromide in Vegetable Production

Compost sources were used to determine long-term influence on common vegetable cropping systems (tomato, pepper, and cucumber). Three sources of Controlled Microbial Compost (CMC) (20 yd3/A) amended with fumigant Telone-C35 (35 gal/A) and Trichoderma-382 [2.5 oz/yd.3 (T-382)] were used during 3 consecutive years. Tomato showed statistic differences (1%) among compost treatments with higher total yields when CMC was combined with Telone-C35 (21%) and T-382 (8.2%). All treatments but Bio-Compost and control presented al least 25% more marketable yield per acre. No differences in fruit size were found for tomato, except for medium-size fruit when Telone C-35 was added. The CMC alone or combined with Telone C-35 and T-382 increased the total plant dry weight at least 18.6%. Pepper crop showed statistic differences with higher number of No. 1 fruit size when CMC was combined with Telone C-35 and T-382. Number of culls per acre decreased for all three compost sources, with no differences from the control. Cucumber yields differed among treatments for total and marketable yields and No.1 size fruit per acre. Best yields were achieved with CMC and when mixed with Telone C-35 and T-382. The lower numbers of culls per acre were found with Bio-Compost and Lexington sources and CMC+T-382. Total plant dry weight was increased in at least 24% when Bio-Compost or CMC compost were used alone or combined with Telone-C35 or T-382. CMC increased root knot nematode soil counts and percentage of root galling, but tended to improve root vigor in cucumbers. It seems that compost sources combined with Telone C-35 or T-382 could improve the cropping management as alternative to methyl bromide. Weed responses will also be discussed.

Diversity of Landraces of the White-flowered Gourd (Lagenaria siceraria) and its Wild Relatives in Kenya: Fruit and Seed Morphology

Kenyan landraces of the cultivated white-flowered gourd Lagenaria siceraria have highly variable morphology. In order to reveal the inter- and intra-specific variation in fruit and seed morphology in L. siceraria and its wild relatives in Kenya, various traits were examined in a total of 425 strains from L. siceraria (269), Lagenaria sphaerica (124), Lagenaria abyssinica (27) and Lagenaria breviflora (5). Data analysis revealed the following patterns: (1) L. siceraria is more diverse than its wild relatives in both qualitative and quantitative and fruit traits are more variable than seed traits within each species. (2) Principal component analysis of L. siceraria with 15 quantitative traits showed a continuous variation among strains, in which general size factor of fruit and seed, shape factor of fruit and shape factor of seed were the principal causes of variation. (3) No correlation was found between fruit and seed shape, or between size and shape. (4) Image analysis with elliptic Fourier descriptors revealed continuous shape variation in the landraces of L. siceraria. Fruit shape features such as the contrast between a wide base with a distinct handle, and a slender base with an indistinct handle and the degree of bulge of the elongated handle (bilobate shape) were evaluated quantitatively. (5) Analysis of variance of 12 quantitative traits based on the progeny test demonstrated that the degree of heterozygosity is considerably low in the white-flowered gourd existing in the natural environment in Kenya. (6) The quantitative evaluation of the intra-specific variation in fruit and seed in L. siceraria was possible, but it was difficult to classify the landraces into distinct groups. Most of the variation observed in the cultivated L. siceraria, including differences in fruit size and shape, shell thickness and handle development, probably resulted from selection by the local human population.

(230) Genetic Differences in Sweet Cherry Fruit Size Are Determined by Cell Number and Not Cell Size

Although maximizing fruit size is critical for profitable sweet cherry (Prunusavium L.) production, little is known about the cellular differences among and between cultivars that contribute to fruit size differences. A wide range of fruit size exists among sweet cherries, and, due to cultural and environmental differences, significant variation exists among genetically identical fruit from the same cultivar. To determine the relative contributions of flesh cell number and cell size to final fruit size in sweet cherry, equatorial sections of three cultivars with a wide range in final average fruit size [`New York 54' (NY54; 1.4 g fresh weight, 11.8 mm diameter), `Emperor Francis' (EF; 6.1 g, 21.0 mm), and `Selah' (12.8 g, 25.5 mm)] were created from mature fruit. Cells intersecting a transverse line were counted and average cell length was calculated. The average cell numbers were significantly different (P ≤ 0.05) between `NY54', `EF', and `Selah' (26.7, 47.4, and 83.2, respectively), indicating that flesh cell number is the major contributor to differences in fruit size between cultivars. Flesh cell numbers of `NY54', `EF', and `Selah' were similar at bloom and increased rapidly for a short duration after fertilization, suggesting a key developmental period for fruit size differences. To determine the contribution of cell number differences to variation in fruit size within a cultivar, fruit from `Bing' and `Regina' trees exhibiting a range of size due to cultural and environmental differences were measured. In both cases, average cell number was not significantly different (P = 0.9, P = 0.3, respectively), while average cell size was (P ≤ 0.05), further indicating fruit flesh cell number is a genetically controlled trait.

Spur Characteristics, Fruit Growth, and Carbon Partitioning in Two Late-maturing Japanese Pear (Pyrus pyrifolia Nakai) Cultivars with Contrasting Fruit Size

The aim of this study was to investigate the roles of spur characteristics and carbon partitioning in regulating cultivar differences in fruit size of two late-maturing japanese pear cultivars, `Atago' and `Shinkou'. The study of spur characteristics showed that the two cultivars displayed different patterns in leaf development, flower characteristics, fruit growth, and shoot type. In contrast to `Atago' with dramatically larger fruit, `Shinkou' is a heavily spurred cultivar with a higher total leaf area and leaf number per spur early in fruit growth, less vegetative shoots, and smaller fruit but larger core. No significant differences were obtained in specific leaf weight, leaf thickness, chlorophyll content, and net photosynthesis of mature leaves, and seed number per fruit between the two cultivars. The results of trace experiment with 13C revealed that on a spur basis, there were no significant differences in the amount of 13C assimilate produced by spur leaves on each labeling date except at 190 days after anthesis, however, there were highly significant differences in the amount of 13C allocated to fruit between cultivars. Moreover, a higher amount of 13C assimilates was allocated to `Atago' flesh (or fruit) than that in `Shinkou'. Analysis of relative sink strength (RSS) indicates that the sink strength of fruit was dominant over those of other organs in the spur measured in both cultivars except at the early stage of fruit growth. `Atago' exhibited a greater RSS of fruit and lower losses of 13C for respiration and export than `Shinkou'. These results suggest that the movement of photosynthates into the fruit was determined by sink strength of the fruit rather than the source strength in the two cultivars.

Effects of Reflective Sheet Mulching on Net Photosynthesis, Leaf Character and Fruit Quality of Cherry and Pear

To clarify the effect of reflective sheet mulching on photosynthesis of fruit tree canopies, we investigated, in sweet cherry and pear orchards, the photosynthetic photon flux density (PPFD) reflected from sheet-covered ground, the difference in net photosynthetic rate (Pn) between sheeted and unsheeted (control) plots, and the effects of long-term mulching on leaf character and fruit quality. In complementary greenhouse experiments, we investigated thePn of leaves illuminated by various combinations of a range of artificial PPFDs at the abaxial and abaxial surfaces. Though the maximum reflected PPFDs from the control plots distributed below 10μmol m-2s-1in the cherry and 20μmol m-2s-1in the pear, those from the sheeted plots were around 200 μmol m-2s-1. Combining these results with those obtained in the greenhouse experiments led us to estimate that the mean increment ofPnprovided by mulching would be about 2.1 μmol CO2m-2s-1for cherry and about 3.2 μmol CO2m-2s-1for pear. The observed increments ofPnin the lower leaf layers of mulched trees were discussed. Long-term mulching resulted in leaves with sun leaf character and improved the coloring of cherry fruit, though there was no difference in fruit size between the mulched and unmulched plots for either cherry or pear.

Soluble Solids Accumulation in `Valencia' Sweet Orange as Related to Rootstock Selection and Fruit Size

Juice quality of `Valencia' sweet orange [Citrus sinensis (L.) Osb.] trees on Carrizo citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] or rough lemon (C. jambhiri Lush.) rootstocks was determined for fruit harvested by canopy quadrant and separated into size categories to ascertain the direct role of rootstock selection on juice soluble solids concentration (SSC) and soluble solids (SS) production per tree of citrus fruit. SS production per fruit and per tree for each size category was calculated. Juice quality was dependent on rootstock selection and fruit size, but independent of canopy quadrant. Fruit from trees on Carrizo citrange had >20% higher SSCs than fruit from trees on rough lemon, even for fruit of the same size. Large fruit accumulated more SS per fruit than smaller fruit, despite lower juice content and SSC. Within rootstocks, SS content per fruit decreased with decreasing fruit size, even though SSC increased. Rootstock effect on juice quality was a direct rather than an indirect one mediated through differences in fruit size. The conventional interpretation of juice quality data that differences in SSC among treatments, e.g., rootstocks or irrigation levels, or fruit size, are due to “dilution” of SS as a result of differences in fruit size and, hence, juice volume, is only partly supported by these data. Rather, accumulation of SS was greater for fruit from trees on Carrizo citrange than rough lemon by 25% to 30%.

Berry size and vine water deficits as factors in winegrape composition: Anthocyanins and tannins

Soluble solids, seed tannin, skin tannin, and skin anthocyanin were measured in fruit from Cabernet Sauvignon vines that had experienced either High, Control or Low water status during ripening. Berries from each treatment were segregated into 6 size categories at harvest in order to test independently for relationships due to size compared with those due to water deficits. Berry content of all solutes increased approximately in proportion to the increase in berry size. Deviations from proportionality caused Brix and anthocyanin concentration (mg per unit berry fresh mass) to decrease, and the concentration of skin tannin to remain unchanged or decrease slightly with increasing berry size. The concentration of seed tannin did not decrease and appeared to increase with berry size in multiple-seeded berries. In comparison with skin tannin or anthocyanin content, seed tannin content varied more with berry size and less with vine water status. In addition to decreasing berry size, water deficits increased the amount of skin tannin and anthocyanin per berry and the concentrations of skin tannin and anthocyanins, but did not significantly affect the content or concentration of seed tannin. The results show that there are effects of vine water status on fruit composition that arise independently of the resultant differences in fruit size. The effect of vine water status on the concentration of skin tannin and anthocyanin was greater than the effect of fruit size on those same variables. However, the increases in skin tannin and anthocyanin that accompanied water deficits appear to result more from differential growth sensitivity of inner mesocarp and exocarp than direct effects on phenolic biosynthesis.

Rootstock Effects on Growth, Cell Number, and Cell Size of `Gala' Apples

The effects of rootstock on growth of fruit cell number and size of `Gala' apple trees (Malus domestica Borkh) were investigated over three consecutive seasons (2000-02) growing on Malling 26 (M.26), Ottawa-3, Pajam-1, and Vineland (V)-605 rootstocks at the Peninsular Agricultural Research Station near Sturgeon Bay, WI. Fruit growth as a function of cell division and expansion was monitored from full bloom until harvest using scanning electron microscopy (SEM). Cell count and cell size measurements showed that rootstock had no affect on fruit growth and final size even when crop load effects were removed. Cell division ceased about 5 to 6 weeks after full bloom (WAFB) followed by cell expansion. Fruit size was positively correlated (r2 = 0.85) with cell size, suggesting that differences in fruit size were primarily a result of changes in cell size rather than cell number or intercellular space (IS).

BREEDING FOR FRUIT QUALITY

While fruit breeding programs have many different goals, including resistance to abiotic and biotic stress, tree architecture, precocity, and productivity, they all have in common the need to develop high quality fruit. Fruits come in a wide spectrum of size, flavor, color, firmness, and texture. Quality is defined differently for each fruit species and consists of many attributes. For some species, high quality flesh texture is crisp while in others it is soft and melting. Some fruit require a balance of acidity and sweetness while quality in others is simply defined by the degree of sweetness. This paper reviews the physiological and genetic basis for fruit quality traits and presents various approaches for improving fruit quality by breeding. INTRODUCTION Fruit breeding programs have a wide range of specific objectives such as increased cold hardiness or disease resistance. However, all commercial scion releases must have high quality fruit. It does not matter how disease resistant or productive the tree may be, if the fruit is not of acceptable quality it will not be a commercial success. Fruit quality is complex. There are many definitions and standards set by each industry but the simple definition of fruit quality is: Whatever the consumer desires (Barritt, 2001; Elia, 2001; Kupferman, 2002). Since people are different, their desires and ideas of quality are different and breeders need to provide alternatives to meet these market needs. How does the consumer perceive quality? The consumer initially judges quality by the appearance of the fruit at the point-of-sale and then by the taste of the fruit. The appearance will determine the first buy but taste will determine the return buy (Kader, 2002). The challenge for breeders is to provide an attractive fruit with desired taste that will survive the process of reaching the consumer. Attractiveness is usually based on fruit size and color, and taste is generally reflected on a combination of texture, flavor, aroma, and sugar to acid ratios. The process of getting the fruit to the consumer is dependent on the rate of softening and the overall control of the ripening process. This paper reviews the physiology of these traits and describes some new approaches for improving quality traits in fruit. FRUIT QUALITY TRAITS Appearance The characteristics that affect the appearance are primarily size and color. Consumer surveys in peach and apple have shown that bigger is better and consumers are willing to pay enough more to make larger fruit more profitable (Parker et al., 1991; Bruhn, 1995; Kupferman, 2002). Bright, clear colors are preferred (Francis, 1995). 1. Size. Fruit size has a large genetic component thus selecting for larger fruit is relatively straight-forward (Janick and Moore, 1996). Fruit size is a function of cell number, cell volume, and cell density (Coombe, 1976; Scorza et al., 1991). In tomato, introgressing wild type germplasm with small fruit size with commercial type germplasm with large fruit, a fruit size quantitative trait locus, fw2.2, responsible for 30% of the difference in fruit size was isolated. The gene was cloned and found to be associated with altered cell division in ovaries. Interestingly, the overall fruit yield in small and large-fruited plants was the same as the small-fruited isogenic lines produced more fruit than the large-fruited Proc. XXVI IHC – Genetics and Breeding of Tree Fruits and Nuts

Influence of branch autonomy on fruit, scaffold, trunk and root growth during stage III of peach fruit development.

We studied the influence of branch autonomy on the growth of reproductive and vegetative organs by establishing different patterns of fruit distribution within and between large branch units (scaffolds) in mature peach trees (Prunus persica (L.) Batsch cv. 'Elegant Lady'). Different patterns of fruit distribution were established by defruiting either whole scaffolds (uneven fruit distribution between scaffolds; US) or several selected hangers (small fruiting branches) per tree (uneven fruit distribution between hangers; UH). The effects of these patterns were compared with the effects of an even fruit distribution treatment (EVEN) in which fruits were thinned to achieve maximum uniformity of fruit distribution within the canopy. The desired fruit loads were obtained by differentially thinning the remaining bearing parts. On a tree basis, the response of mean fruit mass to fruit load was strongly affected by fruit distribution. The steepest mean fruit mass to fruit load relationship was found in US trees, whereas the relationship in UH trees was intermediate between the US and EVEN trees. On a scaffold basis, differences in fruit size between EVEN and US trees with similar fruit loads, though statistically significant, were relatively small, indicating that scaffolds were almost totally autonomous with respect to dry matter partitioning to fruit during the final stage of peach fruit growth. Hangers also appeared to exhibit significant autonomy with respect to the distribution of dry matter during the final phase of fruit growth. Branch autonomy was evident in scaffold growth: defruited scaffolds in the US treatment grew more than fruited scaffolds, and fruit distribution treatments had little impact on scaffold cross-sectional area on a tree basis. On the other hand, as observed for fruit growth, branch autonomy did not appear to be complete because the fruited scaffolds grew more in US trees than in EVEN trees under heavy cropping conditions. However, the effect of fruit distribution occurred only over short distances, and was negligible on organs located farther away from the source of heterogeneity (fruits), such as the trunk and roots.

Effect of Planting Density on Fruit Size, Light-Interception and Photosynthetic Activity of Vertically Trained Watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) Plants

The effect of planting density on fruit size of vertically trained watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) plants was investigated with regard to light-interception character-istics and photosynthetic production. Watermelon plants, grafted on bottle gourd, were grown in a glasshouse at different planting densities. Two vines per plant were allowed to grow and trained vertically. One hand-pollinated fruit per plant was set around the 15th node on either vine. The solar radiation and photosynthetic rate of individual leaves during fruit development period were determined by an integrated solarimeter film and a portable photosynthesis system, respectively. Fruit size was significantly decreased as the planting density increased, whereas soluble solids content of the fruits was affected little. The solar radiation and the photosynthetic rate of the individual leaves gradually decreased as the leaf position became lower at all planting densities on account of shading; those at lower leaves tended to decrease as the planting density increased. Fruit size was closely related to both the total solar radiation and the photosynthetic production per plant. In conclusion, the difference in fruit size among the planting densities is attributed to the photosynthetic productivity of the whole plant, which is mainly a function of the total solar radiation. This paper appears to be the first trial relating the influence of light interception and photosynthetic rates in high density plantings of vertically trained watermelon plants on fruit size.

Natural alleles at a tomato fruit size quantitative trait locus differ by heterochronic regulatory mutations.

fw2.2 is a major quantitative trait locus that accounts for as much as 30% of the difference in fruit size between wild and cultivated tomatoes. Evidence thus far indicates that fw2.2 alleles modulate fruit size through changes in gene regulation rather than in the FW2.2 protein itself. To investigate the nature of these regulatory changes and the manner in which they may affect fruit size, a pair of nearly isogenic lines has been subjected to detailed developmental, transcriptional, mitotic, and in situ hybridization studies. The results indicate that the large- and small-fruited alleles of fw2.2 differ in peak transcript levels by approximately 1 week. Moreover, this difference in timing of expression is associated with concomitant changes in mitotic activity in the early stage of fruit development. The changes in timing of gene expression (heterochronic allelic variation), combined with overall differences in total transcript levels, are sufficient to account for a large portion phenotypic differences in fruit weight associated with the two alleles.

Fw2.2 Directly Affects the Size of Developing Tomato Fruit, with Secondary Effects on Fruit Number and Photosynthate Distribution

fw2.2 is a quantitative trait locus responsible for approximately 30% of the difference in fruit size between large, domesticated tomatoes (Lycopersicon esculentum Mill.) and their small-fruited wild relatives. The gene underlying this quantitative trait locus was cloned recently and shown to be associated with altered cell division in ovaries (Frary et al., 2000). However, it was not known whether the change in fruit size is associated with other changes in plant morphology or overall fruit yield-changes that could potentially cause the fruit weight phenotype. To shed light on this issue, a detailed comparison was made between nearly isogenic lines differing for alleles at this locus to search for pleiotropic effects associated with fw2.2. Field observations show that although the small-fruited nearly isogenic line produced smaller ovaries and fruit as expected, this was compensated by a larger number of fruit-due mainly to a significantly greater number of inflorescences-but with no net change in total fruit mass yield. This strongly suggests that fw2.2 may have a pleiotropic effect on how the plant distributes photosynthate among fruit. In a flower removal experiment to control for differences in inflorescence size and number, fruit size remained significantly different between the nearly isogenic lines. These observations indicate that the primary effect of fw2.2 is in controlling ovary and fruit size, and that other associated phenotypic effects are secondary.

Diurnal changes in non-structural carbohydrates in leaves, phloem exudate and fruit in ‘Braeburn’ apple

Diurnal changes in carbohydrates in leaves, phloem exudate and within fruitwere determined in apple trees grown under high, low or no crop load. Inleaves, diurnal patterns of carbohydrate concentrations were most distinct inhigh-cropping trees and least so in non-cropping trees. In phloem exudate,sorbitol comprised about 65–70% of sugars and sucrose30–35%, with clear diurnal patterns in the amounts. Phloemexudates from stalks of sun and shade fruit were similar. Fruit carbohydratesshowed little diurnal variation. Crude fruit extracts showed little differencein sucrose synthase (SS, EC 2.4.1.13) activity between crop loads, whilesucrose phosphate synthase (SPS, EC 2.4.1.14) activity in high-cropping treespeaked at night and in low-cropping trees in the morning. SPS activity inshade fruit from high-cropping trees was only half of that in sun fruit (atmidday). Results indicate that the greater weight of individual fruit from lowcrop loads is primarily due to greater supply from the source, rather thanhigher metabolic activity in the sink, compared to fruit from high crop loads.In contrast, fruit size differences in sun and shade fruit of high-croppingtrees appear to be due to differences in sink metabolism rather than supplyfrom the source.

Matted-row Strawberry Production using Landscape Fabrics and Organic Mulch for Weed Control

Three landscape fabrics, Magic Mat®, a heavy black plastic woven fabric with a fuzzy underside; Weed Mat®, a thin black plastic sheet with small holes; and Typar®, a dark gray spun bonded material, with and without a cover of organic oak bark mulch, were evaluated for weed control and ability of strawberry plant roots to establish through the fabrics over a 4-year period. Landscape fabrics reduced weed numbers for the first 3 years in comparison with the bare ground treatment. With few exceptions. the organic mulch did not improve the weed control capability of landscape fabrics. Fruit yield for the Weed Mat and Magic Mat treatments did not differ from the bare ground treatment, but was lower for the Typar treatment when averaged over organic mulch treatments. Fruit yield was higher where the organic mulch was used when averaged over all landscape fabric treatments. Fruit size was slightly larger for the bare ground and smallest for the Typar treatments during the first harvest season, but there was no difference in fruit size by the third year of harvest. Fruit size for the organic mulched plots was slightly larger than that for the unmulched plots the second year of harvest, but there was no difference for the first or third years. The number of strawberry runner plants that rooted and plant row vigor were greater for the Weed Mat, Magic Mat and plots without the landscape fabric than for the Typar plots, particularly in the second and third season. Rooting of runner plants and plant row vigor was better with organic mulch. Landscape fabric tended to reduce extent of rooting, especially in the first season, but it was improved by the application of organic mulch.