Search Results
Abstract
Three diploid taxons (Vaccinium darrowi Camp, V. elliottii Chapm., and interspecific V. darrowi x V. elliottii) were treated with various colchicine concentrations and treatment durations to determine the best method for inducing autopolyploidy in in vitro blueberry cultures. Shoot-tip cuttings were the best in vitro planting material for induction of shoots with increased diameter, an indicator of polyploidy. Tetraploids were produced at colchicine concentrations from 0% to 0.20%. The best treatment combinations were genotype-dependent.
Variation was studied within and among five Vaccinium taxa for the flower parameters corolla length, corolla aperture diameter, stigma location relative to the apex of the corolla tube, position of the anthers relative to the stigma and to the apex of the corolla, and style length. The objective was to determine whether there was enough genetic variation to breed cultivars with flower shapes that might favor pollination by a wider range of bee species. The taxa studied were cultivated rabbiteye (V. ashei Reade), cultivated southern highbush (mainly V. corymbosum L. with up to 30% introgression from V. darrowi Camp), F1 V. ashei × V. constablaei A. Gray hybrids, V. darrowi, and V. elliottii Chapm. Vaccinium elliottii flowers differed from all others in having short styles that were not exserted from the corolla tube. Vaccinium elliottii was also unusual in that the end of the anther tube extended nearly to the stigmatic surface. Vaccinium ashei corollas were longer and had smaller apertures than those of southern highbush, possibly making them less suitable for honeybee (Apis) pollination. For corolla length and aperture diameter, F1 V. ashei × V. constablaei hybrids were similar to southern highbush, indicating that V. constablaei introgression could be used to breed hexaploid cultivars with shorter, more open flowers. Large clone-to-clone variation within taxa for each flower characteristic indicates much potential for changing the shape of the blueberry flower by breeding, if the shape that maximizes fruit set can be determined.
Data from a four-parent diallel, involving one highbush (Vaccinium corymbosum L.) clone and three interspecific hybrids grown on mineral soil unamended with organic matter, were analyzed to determine combining ability effects for six traits: plant size, berry size, the number of days between flowering and fruiting (# DBF&F), the ratio of total fruit weight to canopy volume (TFW: CYV), days to fruit ripe, and yield. General combining ability effects were significant for all characters tested, except yield and berry size in 1984. Specific combining ability effects were significant for plant size in 1983, #DBF&F in 1984, TFW: CYV in 1984, and berry size in 1985. Vigorous and productive highbush cultivars can be developed for mineral soils by using the interspecific clones from this study and their selected recombinant to combine the genes for plant vigor with the high-quality fruit traits of highbush cultivars.
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.
A tetraploid blueberry population resulting from a cross of US 75 {a tetraploid hybrid of Fla 4B [a selection of Vaccinium darrowi Camp (2n = 2x = 24) × `Bluecrop' [(V. corymbosum L. (2n = 4x = 48)]} × `Bluetta' (4x) was used to generate a genetic linkage map of US 75 by randomly amplified polymorphic DNA (RAPD) analysis. One hundred and forty markers unique for Fla 4B that segregated 1:1 in the population were mapped into 29 linkage groups that cover a total genetic distance of 1288.2 cM, with a range of 1.6 to 33.9 cM between adjacent markers. The map is essentially of V. darrowi because US 75 was produced via a 2n gamete from Fla 4B and only unique markers for Fla 4B were used. Therefore, all the chromosomes of V. darrowi could be represented in the map.
Fifteen highbush (or highbush hybrid) blueberry cultivars (Vaccinium corymbosum Linnaeus), two rabbiteye blueberry cultivars (V. ashei Reade), and one southern lowbush (V. darrowi Camp) selection from the wild were examined using seventeen 10-base RAPD and seven 15- to 18-base SSR-anchored primers (primers comprised of SSR motifs) in polymerase chain reactions (PCRs). Fifteen RAPD and three SSR markers resulting from these reactions were chosen to construct a DNA fingerprinting table to distinguish among the genotypes included in this study. Similarity values were calculated based on 132 RAPD and 51 SSR bands, and a dendrogram was constructed based on the similarity matrix. The V. ashei cultivars and V. darrowi selection grouped out separately from the V. corymbosum cultivars as expected. However, estimates of relative genetic similarity between genotypes within the V. corymbosum group did not agree well with known pedigree data and, thus, indicated that RAPD and SSR data did not accurately assess the genetic relationships of cultivars within this species.
Loss of freeze tolerance, or deacclimation, is an integral part of winter survival in woody perennials because untimely mid-winter or spring thaws followed by a hard freeze can cause severe injury to dehardened tissues. This study was undertaken to investigate deacclimation kinetics, particularly the timing and speed, of five blueberry (Vaccinium L.) cultivars (`Bluecrop', `Weymouth', `Ozarkblue', `Tifblue', and `Legacy'), with different germplasm compositions and mid-winter bud hardiness levels, in response to an environmentally controlled temperature regime. Based upon bud cold hardiness evaluations in 2000 and 2001, `Tifblue', a Vaccinium ashei Reade cultivar, was one of the least hardy and the fastest to deacclimate; `Bluecrop', a predominantly V. corymbosum L. cultivar, was the most hardy and the slowest to deacclimate; and `Ozarkblue', a predominantly V. corymbosum cultivar but including southern species V. darrowi Camp. and V. ashei, was intermediate in speed of deacclimation. `Weymouth' (predominantly V. corymbosum) and `Legacy' (73.4% V. corymbosum and 25% V. darrowi) were slow to intermediate deacclimators. Deacclimation rates did not correlate strictly with mid-winter bud hardiness. Data suggest that the southern germplasm component V. ashei may be responsible for the observed faster deacclimation whereas both southern species, V. darrowi and V. ashei, may contribute genes for cold sensitivity. Strong positive correlations between stage of bud opening and bud cold hardiness existed in both years (r = 0.90 and 0.82 in 2000 and 2001 study, respectively). Previously identified major blueberry dehydrins, 65-, 60-, and 14-kDa, progressively decreased in their abundance during incremental dehardening in `Bluecrop', `Weymouth', and `Tifblue'. However, down-regulation of the 14-kDa dehydrin most closely mirrored the loss in cold hardiness during deacclimation, and, therefore, may be involved in regulation of bud dehardening. Because differences in deacclimation rate were clearly evident among the genotypes studied, rate of deacclimation of the flower buds of blueberry should be an important consideration in breeding to improve winter survival.
Abstract
Date of 50% anthesis, date of 50% fruit ripening, length of fruit development period, fruit size, flavor, scar and color were determined for random samples of V. darrowi Camp, V. elliottii (Chapm.) Small, V. fuscatum Ait., and V. myrsinites Lam. growing in their native habitats in Alachua County, Florida. Mean berry weight ranged from 25.1 eg for V. fuscatum to 17.8 eg for V. myrsinites. V. elliottii flowered and ripened early, with only 60 days from flowering to ripening for 5 plants. V. myrsinites and V. darrowi flowered late, about 1 to 2 weeks after commercial V. ashei Reade, but ripened with V. ashei. Fruit ranged from shiny black to moderately glaucous for V. elliottii and V. darrowi but was black for V. fuscatum and V. myrsinites. Variance analysis suggested that selecting the best clone within a species is almost as important as selecting the best species in breeding most traits.
Morphological characteristics of many derivatives from Vaccinium arboreum Marsh × Vaccinium section Cyanococcus crosses were studied. The purpose of the study was to determine if V. arboreum traits were being inherited and expressed in hybrid progeny and to identify characteristics that would enable hybrid field identification. This study focused on the F1 hybrids of V. darrowi Camp × V. arboreum (F1 hybrids) and the open-pollinated progeny of the F1 hybrids [mother is known (MIK)]. Also included in the study were the parents: V. darrowi, V. arboreum, and V. corymbosum L. (pollen parent of the MIKs). Many leaf, flower, and fruit characteristics were measured for all five taxa. Leaf characteristics included length, width, and presence or absence of stalked glands, pubescence, and marginal bump glands. The floral characteristics measured were corolla length and width, corolla aperture, pedicel length, peduncle length, bracteole length and width, and the presence or absence of anther awns and bracteoles. Berry and seed mass were the fruit characteristics investigated. Four unique V. arboreum traits were found to be expressed in the F1 and MIK hybrid populations. These were the presence of anther awns, large seed size, bracteole shape, and marginal glands. These traits should permit field identification of hybrid plants.
Diploid plants in Vaccinium section Cyanococcus, including plants of V. darrowi Camp, V. atrococcum. Heller (diploid V. corymbosum L.), a V. atrococcum × V. darrowi F1 hybrid, and a V. atrococcum × V. elliottii Chapmn. F1 hybrid, were hand pollinated in a greenhouse with pollen from diploid V. arboreum Marsh. (Section Batodendron). The resulting seeds were germinated and the seedlings were transplanted to a high-density field nursery. Forty of these F1 intersectional hybrids were selected after 2 1/2 years and transplanted to a 1.5 × 4-m spacing. Most of these plants were vigorous and flowered heavily in subsequent years, but only a small percentage of the flowers produced fruit. In 1990, however, >4000 berries were harvested from the 35 surviving plants. Open-pollinated seed from a much smaller number of berries was planted in Dec. 1987; these seeds produced ≈200 seedlings, some of which had moderate to high fruit set in a field nursery in 1989. Six of these seedlings, which were selected for high vigor, high fruit set, and characteristics intermediate between section Cyanococcus and section Batodendron, had fruit set ranging from 19.4% to 92.7% when pollinated with pollen from tetraploid V. corymbosum cultivars. One of the six seedlings was highly self-fruitful, and some intercrosses among the six seedlings produced much viable seed. Large-scale introgression of V. arboreum genes into tetraploid highbush cultivars likely will be possible by the methods used in this study.