Progress 10/01/01 to 09/30/07
Outputs
Breeding low-chill southern highbush cultivars by phenotypic recurrent selection gave rise to the cultivars Emerald, Jewel, Abundance, Springwide, and Springhigh. Dew-point temperatures during frost periods in Florida demonstrated pronounced diurnal variation, with two maxima and two minima per 24-hour period. The primary maximum was 1 to 2 hours after sunrise, when overnight dew or frost was evaporating. A secondary maximum occurred after sunset, just before dew or frost began to form. Dew point minima occurred just before sunrise, when dew or frost had removed the most water vapor from the boundary layer air, and in mid-afternoon, at the hour of maximum mixing down of dry air from above. The amplitude of the diurnal variation averaged 4 to 5C degrees. Clones of Vaccinium darrowi (diploid) that were atypically tall (2 to 3m) but had small, evergreen leaves typical of the species were selected from the Ocala National Forest in central Florida and crossed with tetraploid
southern highbush cultivars. Several of the V. darrowi clones gave unusually high numbers of tetraploid hybrids in these crosses (averaging about one hybrid per ten pollinated flowers). Very few triploid hybrids were produced. First-generation hybrids were highly variable in height, time of flowering, extent of evergreen leaves, strength of spring growth flush, and in berry characteristics. Several typical V. darrowi clones (30 cm tall and highly glaucous leaves) were selected from the bluffs of the Appalachicola River near Chattahoochee, Florida and were crossed as females with tetraploid cultivars. Most clones produced very few hybrids (fewer than 1 hybrid per 300 pollinated flowers), but one exceptional clone produced over 100 fertile hybrids per 300 flowers. Thousands of V. arboreum seeds were treated with colchicine to induce polyploidy. Three tetraploid plants were selected after they flowered on the basis of plant morphology and pollen diameter. Two of these shed pollen
abundantly but one was nearly male sterile. Their pollen was used in crosses with tetraploid highbush cultivars. Resulting seed set per pollinated flower was about 25% of what is normal for highbush x highbush crosses. More than 100 seedlings have been grown but not yet evaluated.
Impacts
Southern highbush blueberry cultivars are making it possible to harvest fresh blueberries from Florida, Georgia, and California during April and May, and from the southern hemisphere during October and November. Using plastic tunnels, harvest of these cultivars can be extended to February and March in North America. The blueberry cultivars now being grown fall far short of what will be possible with continued breeding. Berry size, berry quality, yield, and ease of production have been greatly improved during the past 30 years, and much additional progress will be possible through recurrent selection. Use of wild germplasm in breeding, including Vaccinium darrowi and V. arboreum, will be important in obtaining better cultivars. V. arboreum is highly drought tolerant, and can be cultivated on upland soils with minimum irrigation. Genetic combinations involving V. arboreum and southern highbush cultivars will eventually allow high-quality blueberries to be grown on corn
and soybean land, rather than on the organic wetland soils required by southern highbush. Differences in local populations of each of the native blueberry species indicates the importance of preserving wild habitat where these blueberries can persist and prosper, free of habitat destruction by farming, urbanization, intensive forestry practices, and invasion by aggressive exotic weedy plant species.
Publications
- Ward, D. B. 2007 and P.M. Vaccinium tenellum is not a native Florida blueberry. Castanea 72:45-46.
- Lyrene, P.M. 2007. Zizyphus jujuba. In: J. Janick and R.E.Paull (eds.). Encyclopedia of Fruits and Nuts. Oxford Univ. Press.
- Lyrene, P.M. 2007. Zizyphus mauritiana. In: J. Janick and R.E. Paull (eds.). Encyclopedia of Fruits and Nuts. Oxford Univ. Press.
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Progress 10/01/05 to 09/30/06
Outputs
Specimens classified as Vaccinium tenellum from Florida were obtained from several herbaria and all were found to be Gaylussacia dumosa. We have concluded that, contrary to previous reports, V. tennellum does not occur naturally in Florida. The success of crosses between V. darrowi (diploid) and cultivated southern highbush cultivars (tetraploid) was highly variable depending on the origin of the V. darrowi plants. Low-growing, glaucous-leaf V. darrowi from south Florida produced few hybrids and the hybrids had very low fertility. Tall-growing V. darrowi from the Ocala National Forest produced far more hybrids, almost all of which were fertile tetraploids. Imbibing seeds of V. arboreum in 0.5 percent aqueous colchicine for 110 hours immediately before planting did not significantly reduce seed germination or seedling vigor. Drip irrigtion was found to reduce the severity of stem blight (Botryosphaeria dothidea) in blueberry plantings on deep sand compared to overhead
irrigation. A southern highbush selection in which one of the 8 great-grandparents was a sparkleberry (V. arboreum) has bush and berry qualities good enough for a commercial cultivar. Crisp texture in blueberry appears to have rather high heritability and, at least in the Florida germplasm, is associated with low fruit acidity.
Impacts
Improved cultivars will improve berry quality, increase yields, and reduce production costs for fresh blueberries harvested during April and October. Cultivars with greater disease resistance and drought tolerance will reduce pesticide and water use in blueberry. production. Cultivars that can be harvested by machine rather than by hand will reduce harvest costs.
Publications
- Padley, L. and P.Lyrene. 2006. Studies with crisp-textured blueberries. (Abstract). HortScience 41:985.
- Lyrene, P.M. 2006. Blueberry. In: Register of new fruit and nut cultivars. List 43. J.R. Clark and C.E. Finn (editors). HortScience 41:1106-1107.
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Progress 10/01/04 to 09/30/05
Outputs
Additional information was gathered on the performance in Florida of three new patented southern highbush blueberry varieties developed at the University of Florida. Springhigh is vigorous and upright, producing large, dark-blue fruit, with good scar and flavor and medium firmness. It ripens a week before the standard variety Star, but it also flowers earlier than Star. Springhigh has excellent field survival and sets fruit even under adverse pollination conditions. Springwide has a very low chill requirement and is best adapted in central Florida. It has a spreading growth habit, leafs well in the early spring, and produces dark-blue berries that are medium to large and have good scar, firmness, and flavor. Plant survival in the field is similar to Star. The plant flowers before Star and ripens 4 days earlier. Abundance is highly vigorous but plant survival is only medium. Fruit set is excellent under adverse pollination conditions. The berry is large with light-blue
color, good firmness and flavor and a small scar that has an occasional tear. The berries ripen 10 days after Star, but yield is high. These varieties came from a recurrent selection program that is concentrated on earliness of leafing and ripening, good plant survival in the field, reliable yield, and good berry quality. The crisp texture found in the berries of blueberry cultivars such as Bluecrisp was found to be highly heritable and seems to be strongly associated with low berry acidity. An allele that is now frequent in the Florida southern highbush breeding program imparts a dwarf phenotype, in which seedlings of high vigor and low apical dominance produce numerous basal sprouts but stay less than 70 cm tall. Some crosses segregate up to 50% dwarf progeny. Stem blight, caused by Botryosphaeria dothidea, appears to be the main cause of death of highbush blueberries in Florida.
Impacts
Improved cultivars will improve berry quality, increase yields, and reduce production costs for fresh blueberries harvested during April and October.
Publications
- Lyrene, P.M. 2004. Blueberries on ice: coping with Florida's frost. Weatherwise 57 (3): 21-24.
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Progress 10/01/03 to 09/30/04
Outputs
Three tetraploid southern highbush blueberry cultivars were introduced and made available for licensing. 'Springhigh' ripens 10 days earlier than 'Star', is very upright, is resistant to stem blight and phytophthora root rot, and has large berries with good scar and medium firmness. 'Springwide' has a very low chill requirement and is intended for areas with winter temperatures like Orlando and Sebring, Florida. 'Abundance' is a mid-season southern highbush cultivar, ripening a few days after Star. It has excellent vigor and high yield potential. Investigations into the nature of the very firm, almost crisp texture of berries of blueberry cultivars such as 'Reveille', 'Bluecrisp', and 'FL00-59' suggest that this is a quantitative trait, with these clones representing the highest part of a continuous distribution for berry firmness. The crisp berries were preferred by most subjects in a 100-subject organoleptic survey. Segregation ratios from selfing and inter-crossing
dwarf selections that occur frequently in our autotetraploid southern highbush blueberry seedling populations suggest that AAAA, AAAa, and AAaa plants are tall, Aaaa plants are dwarf, and aaaa plants are inviable.
Impacts
Improved cultivars will improve berry quality, increase yields, and reduce production costs for fresh blueberries harvested during April and October.
Publications
- Lyrene, P.M. 2004. Flowering and leafing of low-chill blueberries in Florida. Small Fruits Review 3:375-379.
- Lyrene, P.M. and J.W. Williamson. 2003. Blueberry fruit set as related to relative humidity in Florida. Proc. Fla. State Hort. Soc. 116:21-25.
- Lyrene, P.M. 2004. Early-ripening rabbiteye blueberries. Proceedings 2004 Southeastern Regional Fruit and Vegetable Conference. P. 113-116.
- Lyrene, P.M. 2004. Weather and pollination of southern highbush blueberries. Proceedings 2004 Southeastern Regional Fruit and Vegetable Conference. P. 119-124.
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Progress 10/01/02 to 10/01/03
Outputs
More than 100 F1 hybrids were made by pollinating diploid Vaccinium darrowi with pollen from tetraploid southern highbush cultivars. The V. darrowi plants were clones that had not been used before in breeding. Evidence from high percent pollen staining, high fruit set when open pollinated in the field, and high seed content in the berries indicated that most if not all seedlings were tetraploid. Frequent rains and high humidity during the blueberry pollination season in north Florida and southeast Georgia resulted in reduced fruit set in field plantings and revealed that the variety Star is exceptional in producing seedless marketable berries.
Impacts
Improved cultivars will improve berry quality, increase yields, and reduce production costs for fresh blueberries harvested during April and October.
Publications
- Lyrene, P.M., N. Vorsa, and J.R. Ballington. 2003. Euphytica 133:27-36.
- Wenslaff, T.F. and P.M. Lyrene. 2003. Unilateral cross compatibility in Vaccinium elliottii x V. arboreum, an intersectional blueberry hybrid. Euphytica 131:255-258.
- Wenslaff, T.F. and P.M. Lyrene. 2003. Chromosome homology in tetraploid southern highbush x Vaccinium elliottii hybrids. HortScience 38:263-265.
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Progress 10/01/01 to 10/01/02
Outputs
Ten clones of Vaccinium darrowi (diploid), selected from the Florida peninsula for having tall stature and vigorous bushes, were crossed with southern highbush blueberry cultivars (tetraploid). The V. darrowi clones ranged from 1.5 to 3.0 m tall in the forest, the atypically tall stature probably reflecting introgression with diploid V. corymbosum (V. fuscatum race)during the last several hundred years. Several hundred to 1,000 flowers were pollinated on each V. darrowi plant. The seedlings, grown in a field nursery, were highly variable. Approximately 100 seedlings appeared to be interspecific hybrids and had excellent vigor. Those hybrids that are fertile will be backcrossed to southern highbush cultivars in an effort to produce cultivars adapted to warmer areas in Florida. A new southern highbush cultivar,'Sebring', was patented and released to propagators. It has an extremely low chilling requirement and shows early flowering and early leafing in areas where mean
January temperatures average as high as 17 degrees C. Ten thousand new blueberry seedlings from controlled crosses were evalutated in north Florida field nurseries for their ability to produce high yields of high-quality berries during April on vigorous, disease-resistant bushes. The New Jersey cultivar 'Legacy' was found to fruit and leaf well after only 400 chill hours in north Florida if sprayed with hydrogen cyanimide. After a decade of causing little trouble, the cane canker pathogen (Botryosphaeria corticis) has become increasingly widespread on older blueberry farms in north Florida, and resistance to this endemic fungus is being given greater emphasis in the breeding program.
Impacts
New cultivars will be developed that reduce the cost of growing April blueberries in Florida and increase the quality of the berries. The use of new native Florida blueberry plants in breeding cultivars will make blueberries more secure from diseases and will make it possible to select blueberry cultivars with new bush characteristics and new berry flavors and textures.
Publications
- Lyrene, P.M. 2002. Blueberry. In: Register of New Fruit and Nut Varieties. W.R. Okie (ed.). HortScience 37:252-253.
- Lyrene, P.M. 2002. Development of highbush blueberry cultivars adapted to Florida. J. Amer. Pom. Soc. 56:79-85.
- Lyrene, P.M. 2002. 'Brightwell' rabbiteye blueberry. J. Amer. Pom. Soc. 56:66-68.
- Lyrene, P.M. 2002. Market windows for Florida blueberries. Proc. Fla. State Hort. Soc. 114:24-26.
- Lyrene, P.M. 2002. Breeding southern highbush blueberries in Florida. Acta Hort. 574:149-152.
- Lyrene, P.M. 2002. Blueberry breeding for low-chill environments (abstr). HortScience 37:748.
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Progress 10/01/00 to 10/01/01
Outputs
Four Vaccinium darrowi x V. arboreum F-1 hybrids were found to form mostly univalents at first meiotic metaphase. This low chromosome pairing probably explains why few gametes produced by the hybrids, other than 2n gametes, are viable. The number of seeds produced per berry after hand-pollination of southern highbush blueberry flowers on plants that were maintained evergreen in a greenhouse without chilling was much lower than in berries produced by similar pollinations on chilled plants emerging from dormancy in the spring. One hundred random seedlings from four southern highbush blueberry crosses were highly variable in the time and extent of flowering when 2-year old plants were potted from a field nursery in late summer and maintained evergreen in a greenhouse through fall and winter, with temperatures maintained between 10 and 28 degrees C. A few plants underwent concentrated flowering during December and could have produced a full crop of berries during March if
the flowers had been pollinated. Plants of a few southern highbush selections, if kept evergreen, produced parthenocarpic fruit from more than 50% of the flowers in which the style had been removed before pollination. Few fruit were produced after similar treatment of flowers on plants that had lost their leaves and had been chilled before flowering. Evergreen plants of tetraploid V. corymbosum that were capable of parthenocarpic fruit production produced little seed after being pollinated with pollen from diploid V. darrowi, even though they ripened far more berries than plants receiving the same treatment after having been put into dormancy and chilled. Two southern highbush cultivars, Windsor and Millennia, were patented and released to licensed propagators. Both have high yield potential and a chill requirement of 300 to 400 hours below 7 C. The pedigree of Millennia is O'Neal x FL85-69. Two native highbush selections from north Florida that had never before been used in breeding
constitute 50 % of the pedigree of FL85-69.
Impacts
The development of low-chill blueberry cultivars that have more consistent yields, higher fruit quality, and greater plant vigor and disease resistance will make it easier to cultivate highbush blueberries in subtropical areas where berries can be harvested very early in the spring. Development of plants that require no chilling and can produce large crops in a greenhouse during a concentrated season with little or no pollination would make off-season, protected culture of blueberry much easier. Crosses of cultivated highbush blueberries with the wild diploid species V. darrowi and V. arboreum could lead to plants that are adapted to a wider range of soils and also to plants with greater utility as landscape plants.
Publications
- Wenslaff, T.E. and P.M. Lyrene. 2001. Results of multiple pollination in blueberry (Vaccinium elliottii Chapm.). Euphytica 117:233-240.
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