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- Author or Editor: A. D. Draper x
- Journal of the American Society for Horticultural Science x
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.
Abstract
Chromosome pairing in a derived decaploid, 2n=10×=120, (from a colchicine-treated, sterile pentaploid hybrid of Vaccinium ashei Reade × V. corymbosum L.) was chiefly bivalent. Multivalent associations were present in 5 of 16 cells scored at metaphase I, but only 23 chromosomes of the 1,920 observed were involved in multiple pairing. Most of the cells at anaphase I (33 of 35 observed) contained lagging chromosomes which appeared to be non-disjoined bivalents rather than univalents. The decaploid was selfed and crossed with hexaploid, tetraploid, and diploid species. The mean number of seedlings produced per flower pollinated for each ploidy level was low, ranging from 0.04 to 0.09. The mean seedling number produced per self-pollinated flower was considerably higher, 0.92. The percent of pollen which stained in propionocarmine was 8% for the pentaploid parent, 62% for the derived decaploid and 99% for plants of V. ashei and V. corymbosum used as standards for comparison.
Abstract
Studies were conducted on the feasibility of shortening the evaluation period of highbush blueberry (Vaccinium corymbosum L.) selections by propagating by softwood cuttings taken from each of the single-plant selections at the time of fruit evaluation row the following spring. Softwood cuttings were taken from a single plant of 5 early, 5 midseason, and 5 late ripening selections in June, July, and August. July cuttings (60%) rooted better than June (37%) and August (31%) cuttings. Early selections (34%) rooted about the same as midseason (32%) and late (35%) selections. The earlier the cuttings were potted, the larger the root system they developed before frost when grown in an unheated greenhouse. None of the rooted cuttings potted 30 Sept, developed root systems large enough to survive field planting. Supplemental heat and light after potting increased root growth of plants potted 25 Aug. but not those potted 10 Sept. Eighty percent of the plants transplanted to the field survived.
Abstract
Iron chlorosis often develops in blueberries (Vaccinium) grown on soils with a pH above 5.2. Seedlings of 4 blueberry intra- and interspecific progenies, involving V. ashei, V. corymbosum, and V. darrowii, were tested for Fe-efficiency (use of Fe) by growing them in nutrient solutions containing different concentrations of CaCO3 to vary the pH. Plants received Fe during the first 4 harvests (up to 75 days) but received no Fe during the subsequent 2 harvests. The Fe supply for plant growth in the last 2 harvests was limited to that available in the roots. T-65 × US 67 blueberry plants [a 3-species hybrid of V. ashei × (V.darrowii × V. corymbosum)] lowered the pH of the nutrient solution by releasing H+ from their roots which freed Fe from root accumulations and made it available for plant use. ‘Climax’ × T-151 (V. ashei × V. ashei) progeny did not do this. Seedlings of V. corymbosum and those from a cross of V. corymbosum with V. darrowii were intermediate in their response.
Abstract
In a study of breeding of strawberry (Fragaria × ananassa Duch.) for resistance to red stele root rot caused by Phytophthora fragariae Hickman, two different composites of races of the fungus were used to screen seedlings, one with and one without race A-5. In the absence of race A-5, all resistant parents produced between 28.6 to 72.0% resistant seedlings depending upon parental combinations. When race A-5 was included in the composite, two breeding selections that were derived from Fragaria chiloensis Yaquina A clone transmitted more resistance to their seedlings than three other parents in a diallel comparison. Mean squares and variance components were higher for general than for specific combining ability. Resistance is partially dominant for the races involved in this study.
Abstract
Inheritance of albino seedling was studied in progenies of 3 tetraploid cultivated highbush blueberry clones. This mutant character was found to be controlled by a recessive gene at a single locus. All 3 parental clones appeared to be duplex (AAaa) for the marker gene and upon crossing and selfing segregated with ratios that are most likely to occur with tetrasomic inheritance. They segregated approximately 43 normal : 1 albino which is a significant deviation from the expected 35:1 ratio. This deviation is probably due to nonrandom pairing at meiosis of the 4 homologous chromosomes bearing the marker gene.
Abstract
Cultivars of rabbiteye blueberry (Vaccinium ashei Reade) differed in cold requirements for bud break. ‘Woodard’ and ‘Tifblue’ plants required 400 and 600 hr, respectively, of constant chilling (6-7°C) for normal flowering. Two hundred and 400 hr of chilling, respectively, were insufficient for bud break. Additional chilling increased the amount and rate of bud break. Defoliation hastened vegetative bud break but did not affect flower buds.
Interspecific blueberry (Vaccinium spp.) progenies were examined to determine combining abilities and genetic variability for seedling root system size and shoot vigor and to establish whether a large root system is correlated with good growth when plants are grown on a mineral soil and exposed to a moderate soil water deficit. General combining ability (GCA) variance components for root system size and shoot vigor and specific combining ability variance components for shoot vigor were significant. US226, a tetraploid hybrid of V. myrtilloides Michaux × V. atrococcum Heller, had the highest GCA effect for root system size and the lowest GCA effect for shoot vigor. US75 (V. darrowi Camp × V. corymbosum L.) had the highest GCA effect for shoot vigor and was second in GCA effect for root system size. Comparison of the crosses containing G111 (V. corymbosum) with those containing G362 (V. corymbosum) indicates that selecting for the best V. corymbosum clone to start a breeding program seems as important as selecting the mineral soil-adapted parent. Root system ratings were highly correlated with total dry weight of field-grown plants (r = 0.89). The method used in this study to evaluate seedlings for root system size and shoot vigor could be used to eliminate the less vigorous plants from a population before field planting and to evaluate mineral soil adaptability.
The relationship between moisture stress and mineral soil tolerance was studied by placing 10 blueberry (Vaccinium) clones in a Berryland sand soil high in organic matter (Berryland) and a Galestown sandy clay loam soil (Galestown) and subjecting them to one of two moisture regimes. The Berryland and Galestown soils represent an excellent blueberry soil and a mineral soil, respectively. A moderate degree of water stress influenced biomass partitioning in blueberries in a similar manner as stress induced by culture on mineral soil. Berryland control plants on Berryland partitioned more biomass into leaves and produced more dry matter and leaf area than plants on Galestown or those moisture stressed. Net assimilation rate and relative growth rate were not significantly different between soil or moisture treatments. The primary reason for the reduction in absolute growth rate due to soil type or moisture stress was a significantly lower leaf area duration on Galestown soil and in-moisture stressed plants. Clones differed in instantaneous transpiration, leaf conductance, and apparent photosynthesis and the ability to partition biomass into various plant parts. By selecting for increased leafiness, a high photosynthetic rate, and a more energy efficient root system, improvement in mineral soil tolerance should be possible.
Progenies and clones of interspecific hybrid blueberries were evaluated for annual fraction of canopy volume (FCYV) and for difference in fraction of canopy volume between control and stressed plants [FCYV(C) - FCYV(S)] in a moderate water-deficit environment. The FCYV(C) - FCYV(S) data were used to determine combining ability effects. In addition, physiological processes of attached leaves of the clones were monitored with a portable photosynthesis apparatus. Specific combining ability (SCA) effects were significant for FCYV(C) - FCYV(S). The clone with the lowest mean for FCYV(C) - FCYV(S) was US75, a hybrid of Vaccinium darrowi Camp × V. corymbosum L. Clone JU64 (V. myrsinites Lamark × V. angustifolium Aiton) also had a low FCYV(C) - FCYV(S) mean, and its two progenies (JU64 × JU11 and G362 × JU64) had low progeny means. Stomatal conductance was lowered when blueberries were exposed to atmospheric and/or soil moisture stress that resulted in lower transpiration and photosynthesis and increased or equal water-use efficiencies (WUE). Blueberry plants adjusted to moisture stress as the season progressed by lowering stomatal conductance and increasing WUE. In particular, stressed plants of US75 and JU64 had equal or higher WUE values than control plants. US226 was the most drought-susceptible clone in the study, and its stomata did not appear to be as responsive to moisture stress as the other clones. Breeding for higher WUE in a dry environment appears possible with the germplasm used in this study.