Small Fruit Size Research Articles

FLOWERING HABIT AND YIELD OF CALABAZA GENOTYPES

The flowering habit and yield potential of seven calabaza [Cucurbita moschata (Duchesne), Poir.] genotypes were studied in the fall 1991 season. Earliest flowering and mature fruit were produced on bush plants developed from `Burpee Butterbush'. Time of flowering and distance from the crown was intermediate in time in the Florida developed varieties `La Primera' and `La Segunda' and latest in the Puerto Rican developed entries `Borinquen', Linea C Pinta, and Soler. Highest yields were produced by `La Primera' and `La Segunda', whereas, lowest yields were produced by the bush lines because of very small fruit size. Fruit size of `Borinquen' and Linea C Pinta was mostly in the desirable range of 2.3 to 4.5 kg. Most `La Primera' and `La Segunda' fruit were round, `Borinquen', Linea C Pinta, and Soler fruit were flat, and the bush lines produced variable shaped fruit. Further backcrossing to round types is required to overcome the problem of small fruit size and variable fruit shape in the bush lines.

THE INFLUENCE OF RASPBERRY CANE TYPE AND CULTIVAR IN A SCHEDULED PLANTING AND HARVESTING SYSTEM

A new raspberry production system has indicated the feasibility of marketing fresh fruit during August and September, 60-90 days after planting. Full length dormant canes planted late and managed similarly to the strawberry plantings using “waiting bed” plants produced more than 6.0 t/ha. Large canes (>13 mm) produced more laterals and 3 times more fruit than small ones but fruit size was the same. There was little difference between the June 1 and June 20 plantings and `Killarney' outyielded `Festival'. In spite of higher establishment costs, it appears that the higher value for the fruit marketed in late summer and the possibility of using this system for the establishment of a new planting would justify its use.

HORTICULTURAL AND ECONOMIC COMPARISON OF HAND VERSUS MECHANICAL PRUNING IN A HIGH DENSITY FRENCH PRUNE ORCHARD

French prunes (Prunus domestica L.) on myrobalan seedling rootstock were planted in 1981 in an east-west direction with 4.9 m between rows and 2.7 m between trees on a poorly drained Class II soil in Glenn County, CA. A randomized complete block design was used with 8 trees per plot. Trees were pruned by hand to an open-center tree form or pruned by machine to a pyramid form in the dormant or summer season resulting in 6 pruning treatments. This high density system has led to high yields of good quality fruit (9.18 dry tons/acre in 1989, sized at 78 fruit per pound). Hand pruning led to higher yields, larger fruit, lower drying ratios and a greater dollar return per acre than any of the machine pruned trees. Dormant machine pruning led to larger fruit produced than those trees pruned in the summer by machine. Mechanical pruning may be possible for short time periods, but continued practice led to smaller fruit with lower yields than hand pruning. Certain locations within the tree canopy had smaller fruit size and it is within those lower locations where fruit size needs to be improved. These and additional experimental results obtained from 1987 through 1989 growing seasons will be presented.

Effect of temperature during the first 42 days following full bloom on apple fruit growth and size at harvest

The relationship between temperature prevailing during the 42-day period following full bloom (42 DFFB) and fruit size at harvest of four apple cultivars was studied for two seasons. Lower temperatures during the first season resulted in smaller fruit whereas higher temperatures the following season resulted in larger fruit at 42 DFFB. The smaller fruit size at 42 DFFB during the first season was related to lower temperatures during the first, fourth and fifth weeks following bloom. High rates of Starking fruit growth were associated with increased rates of cell division in the cortical region. The relationship between fruit size at 42 DFFB and fruit size at harvest was affected by the number of fruits per cm trunk circumference during the current and the previous season. The relationship between the average mass per fruit at harvest, number of fruits per cm trunk circumference during the current year, kg fruit per cm trunk circumference the previous year, average diameter of fruits at 42 DFFB and number of hours above 14°C until 42 DFFB was calculated for the seasons 1978/79 to 1981/82. A multiple linear regression equation of the form Y=b0+b1X1+b2X2+b3X3+b4X4 was fitted to the data. The number of fruits per cm trunk circumference during the current year was a dominant variable. Although higher temperatures improved the weekly rate of fruit growth during the first 42 DFFB, this effect was offset during most years by an increase in the number of fruits set per cm trunk circumference as a result of more favourable weather conditions during and immediatly after bloom.

The Inheritance of Earliness and Fruit Weight in Crosses between Cultivated Tomatoes and two Wild Species of Lycopersicon

AbstractThe inheritance of earliness and fruit Weight in tomato was studied in tour interspecific crosses. Two cultivated varieties, i.e.‘HS 101’ and “HS 102′, were hybridized with two wild species. L. birsutum f. glabratum‘B 6013’ and L. pimpinellifolium‘A 1921′. Six generations of these crosses were evaluated for these traits and the estimates of gene effects were derived from the generation mean using an epistatic (six parameters) model. There were very wide differences between cultivated and wild species for earliness and fruit weight and in the segregating populations, plants with delayed maturity and smaller fruit size were recorded with high frequency. It was found that the inheritance pattern was mainly governed by additive gene action. Epistatic effects also contributed towards the inheritance of both traits.

Preliminary studies on the use of (2RS, 3RS)-paclobutrazol for fruitlet thinning and growth control of ‘Conference’ pear

SummarySingle foliar sprays of paclobutrazol (PP333) at 300, 1000 or 3000 mg H applied at three different stages from full bloom to petal-fall in a year of average initial sets . and fruit size were equally effective in thinning ‘Conference’ pear, increasing the proportion of large fruits at harvest, but decreasing their absolute numbers. Sprays applied nine days after petal-fall reduced initial sets less effectively and, applied 21 days after petal-fall, were ineffective. Thinning was completed within 25 days after petal-fall. Shoot extension was initially retarded at all three concentrations, but later increased, so that the total growth made during the season was not reduced. Single foliar sprays at 300 or 1000 mg l−1 applied at 70% full bloom in a year of heavy set and small fruit size increased the numbers of large fruits in the >55 mm size category by 66% and decreased those of fruits <55 mm by a similar amount. The increase in the yield of fruits >55 mm and decrease of unsaleable <45 mm fruits was equivalent to about 3 and 2 t ha−1 respectively from a total average yield of about 17.5 t ha−1. In the same experiment, similar sprays counteracted the stimulation in the production of small fruits by sprays of gibberellic acid (GA) applied on the same day, but did not increase the harvest of large fruits. Sprays of paclobutrazol at 30 or 100 mg l−1 applied two weeks after petal-fall and then on three successive occasions at two-week intervals inhibited total extension growth per shoot during the season without affecting initial or final sets, fruit size or flower bud production. Single sprays applied at 100 mg l−1 in July reduced total extension per shoot almost as effectively as the repeated sprays. For more effective control of ‘Conference’ shoot growth, paclobutrazol may have to be sprayed later in the season than commercially recommended. Applied as a blossom thinner, paclobutrazol may increase the yield of large fruits only in years of heavy set and small fruit size, requiring that applications be delayed until set can be judged.

A Nondestructive System for Monitoring Gas Evolution from Small-sized Fruits in the Field

Abstract A nondestructive system for measuring volatile compounds, specifically ethylene, evolved from intact fruit of olive (Olea europaea L.) in the field is described. Polyethylene cans from 35-mm film cartridges are modified with a rubber septum for sampling. The lid is sealed around the fruit peduncle and remains in the field under all conditions. The can is removable to expose the fruit to normal conditions when sampling is not being done. Samples of the atmosphere inside the can are taken with a syringe for gas chromatographic analysis. Background ethylene evolution from the system is low. The system allows repeated monitoring of the same fruit over the duration of a season. Nineteen glues and sealants are evaluated for bonding, phytotoxicity, and ethylene evolution.

Effects of Soil pH, Phosphorus Rates, Deep Tillage Practices, and Clay Additions on Peach Tree Performance in Deep Sandy Soils of North Carolina

Abstract Effects of soil pH, tillage practices, P application, and the addition of clay at the planting site on tree size, fruit yield, fruit size, and tree longevity of peaches [Prunus persica (L.) Batsch] for 20 growing seasons are reported. Because of widespread tree death, ‘Loring’ trees were removed after 9 years and the orchard replanted to ‘Winblo’. Soil pH below 5.6 resulted in poor tree growth, low fruit yield, and small fruit size compared to trees grown in soils at higher pH. In the final 10 years of the experiment, marked improvement in tree size, fruit yield, fruit size, and longevity were evident as soil pH increased. The effect of 3 tillage practices—normal plow to a depth of 20 cm, normal plow to a depth of 20 cm plus a 75-cm-diameter ⨯ 122-cm-deep hole at the planting site, and deep plowing to a depth of 58 cm—varied with cultivar. Both methods of soil profile modification (which penetrated the A2 horizon) resulted in increased yield and tree size compared to normal plowing to 20 cm with ‘Loring’ during the first 9 years. During the final 10 years, fruit yield was lower and tree death greater in the deep-plow plots, but there were no differences in fruit yield, tree size, or tree longevity between the other tillage treatments. Phosphorus rates (0, 15, and 30 kg/ha annually) or clay additions did not influence tree size, fruit yield, or tree survival. Results of this study lend strong support for the maintenance of soil pH above 5.6 and good evidence that increase in tree growth, fruit yield, and tree longevity is further enhanced when soil pH is maintained above 6.0.

Inheritance of Fruit Size in the Cultivated Tetraploid Blackberry [Rubus (Tourn.) L. subgenus Eubatus

Abstract Twelve seedling populations involving large, intermediate, and small-fruited parental clones of tetraploid blackberries were evaluated for fruit size inheritance. The amount and type of variation and the significant deviations from the mid-parent means in seedling distributions indicated that inheritance was quantitative with partial dominance for small fruit size. Maximum heritability, estimated by the genetic variance/phenotypic variance, was 0.76. Narrowsense heritability, estimated by regressing progeny on the mid-parents, was 0.62, indicating that most of the genetic variability (82%) was transmittable through the sexual cycle (gametes). These results suggest that simple breeding procedures based on inter-mating parent clones selected on the basis of their phenotypic performance are likely to produce significant genetic gains in fruit size of blackberries.

Wholeness Retention in Canned Tomatoes

The interaction of cultivar, fruit maturity, and product agitation was related to fruit coherence (‘wholeness retention’) of canned tomatoes. Wholeness retention was measured by expressing drained solids as a percentage by weight of ingoing fresh fruit. Four new cultivars incorporating high colour and increased firmness clearly outperformed 2 older, standard cultivars commonly used by industry. They retained their wholeness under the potentially adverse combination of harvesting at full ripeness plus severe agitation of the canned product, a combination which reduced the wholeness values of the standards to unacceptable or barely acceptable levels. While small fruit size probably contributes to the exceptional wholeness retention of certain cultivars, the excellent wholeness properties of several of the larger, new cultivars cannot be explained on the basis of fruit size. Cut fruits of the latter reveal a characteristic, generous amount and distribution of pericarp tissue relative to locule tissue, suggesting the involvement of cell wall components such as pectic materials, calcium, cellulase, and callose.

The keeping quality of apples in storage as affected by different irrigation regimes

SummaryA study of the effect of different irrigation regimes on the keeping quality in storage of apples (Malus sylvestris cv. Calville de St. Sauveur), showed that a ‘dry’ irrigation regime, consisting of a limited water supply (600 mm) and only four irrigations, was superior to ‘wet’ treatments with a more abundant water supply (800–1200 mm) and more frequent irrigations (10–22). However, the impaired tree growth and the small-sized fruit obtained with the ‘dry’ irrigation regime rule out its commercial use. It is suggested that the inferior keeping quality in storage of fruit subject to the ‘wet’ regimes could be due to a mineral imbalance in the fruit and to the high yield of very large fruit.

Effects of Genetic Parthenocarpy and Gynoecious Flowering Habit on Fruit Production and Growth of Cucumber Cucumis sativus L.1

Abstract Genetically parthenocarpic cultivars produced significantly less fruit fresh weight when pollinated than without pollination. The development of seed was found to have a dual effect on the development of fruit tissue. In terms of percentage dry weight, seed was produced at the expense of fruit tissue, but from the standpoint of percentage fresh weight, seed development stimulated fruit tissue development. Cucumbers appeared to possess a regulatory mechanism that limits the percentage dry weight that can be devoted to fruit and seed production. Seed dry weight accumulated at the expense of fruit rather than vine dry weight. The presence of fruit was observed to have an inhibitory effect on vine growth that was greater when the fruit contained seed than when it did not. Gynoecious flowering habit, compared to monoecious, did not increase the production of mature fruit. The combination of parthenocarpy, gynoecious flowering, small mature fruit size, and perhaps determinate growth, should help maximize fruit production under a single harvest regime, produce a high fruit to vine ratio, and provide flexibility in harvest timing. The results may apply to other crops where the fruit is harvested in a relatively mature state and where the seed constitutes a substantial proportion of the dry weight.

Peach Fruit Abscission as Influenced by Applied Gibberellin and Seed Development1

Abstract Postbloom application of gibberellin A3 (GA3) to open pollinated peach trees prevented seed development in some fruit, and also resulted in the persistence and maturation of both seeded and seedless fruit on the same trees. GA3 temporarily promoted fruit growth and delayed abscission of both seeded and seedless fruit, but the final crop load was not altered. Both seeded and seedless fruit abscised from treated trees during physiological drop. The persisting seedless fruit, therefore, competed successfully with seeded fruit. Seedlessness was associated with smaller fruit size at maturity.

Fruit Size Inheritance in Highbush Blueberries, Vaccinium australe Small1

Abstract Three blueberry progenies from crosses of large-fruited X large-fruited parents were significantly larger in fruit size than 3 progenies from crosses of large-fruited X small-fruited parents. Mean fruit sizes of the 3 large-fruited X small-fruited populations were equal to the fruit size of the smaller fruited parents in each cross, indicating that small fruit size is a dominant character. Large fruit size is not linked with low yield.

Response of Tomato Fruiting to Hydrogen Fluoride as Influenced by Calcium Nutrition

Two varieties of tomatoes grown at 40 to 200 ppm calcium were continuously fumigated with HF throughout flowering and fruit development. Fruit size was directly related to the level of calcium nutrition, and within each calcium treatment the fruits on plants subjected to HF at about 6 μg F/m3 were smaller than those on unfumigated plants. The smaller fruit size was associated with partial or complete seedlessness, suggesting that calcium plays an essential role in fertilization with which fluoride may interfere. Fluoride injury to the tomato foliage was most severe at the lowest calcium level. Treatment with HF at about 8 μg F/m3 produced some injury to tomato foliage but had no apparent effect on fruiting. Evidently fluoride can affect plant fruiting, but considering the severity of the HF treatments required, effects on tomato fruiting probably are of little practical significance. The relationship between fluoride injury and calcium nutrition suggests interference with calcium metabolism as a mechanism of fluoride injury to plants.

SOME EFFECTS ON FRUIT SIZE OF CHROMOSOME 2 OF THE TOMATO

Fruit weights taken from two F2's of 1500 plants indicated that the genes d p o s Lc dil and suf all affect fruit weight. The recessive alleles, except suf and Lc, were associated with small fruit size. The data were analyzed to determine whether this association was the result of linkage or pleiotropic effects. The major effect occurred in the o region, which is some 44 units from the centromere of chromosome 2. The o gene makes the genes oval or pear-shaped instead of spherical, and it is shown that when the locule wall of a spherical fruit and an oval fruit are composed of the same number of cells, the spherical fruit is always heavier. Since cell number is the inherited unit of fruit size, then o is always associated with small size. A gene controlling number of locules, which affects fruit size, is also located in this section of the chromosome. The genes d and s, which are at opposite ends of the present linkage map, both appear to be linked with fruit size genes. It is suggested that these size genes lie in the hetero-chromatin which is adjacent to both ends of the linkage map. The genes dil and suf, which were produced by radiation of the same variety, appear to have pleiotropic effects on fruit size; suf increasing, and dil decreasing fruit size.