Fertility of F1 hybrids and their open-pollinated progeny was studied for the intersectional cross Vaccinium darrowi Camp × V. arboreum Marsh as part of a project to determine the feasibility of using V. arboreum to breed vigorous, drought-tolerant southern highbush blueberry cultivars. The 16 F1 hybrids that were studied were vigorous but very low in fertility. Second generation hybrids [MIKs (mother is known) obtained by open-pollination of the F1s] and MIK derivatives were extremely variable in vigor and fertility, but averaged far higher in fertility than the F1s as evidenced by pollen stainability and amount of pollen produced. F1s produced an average of 0.4 seedlings per 100 pollinated flowers when hand-pollinated in a greenhouse with pollen from V. darrowi, 0.2 when pollinated by V. arboreum and 3.4 when pollinated by cultivated highbush. Some MIKs that were crossed with other MIKs and with cultivated southern highbush were very high in male and female fertility. Female fertility was estimated in greenhouse crosses from fruit set, berry weight, number and weight of seeds, number of plump seeds per berry, and number of seedlings obtained. Male fertility was estimated by pollen stainability with acetocarmine and amount of pollen shed. Chromosome counts showed that three F1s were diploid and that four fertile MIKs were tetraploid. One MIK appeared to be aneuploid. Aneuploidy may explain much of the low fertility found in MIK populations. These results indicate that good progress is being made in returning the hybrid plants to cultivar quality in only a few generations of backcrossing.
Mechanical harvesting systems for processed blueberries (Vaccinium spp.) are available. However, low harvest efficiency and high fruit damage have limited the use of mechanical harvesters for picking blueberries for fresh market to specific cultivars under good weather conditions. New harvesting technology for fresh-market blueberries is needed. The V45 harvester was developed by the U.S. Department of Agriculture in 1994 to harvest fresh-market-quality northern highbush (V. corymbosum) blueberries in Michigan. The current study was performed in Georgia to evaluate the V45 harvester on specially pruned rabbiteye blueberry [V. virgatum (syn. V. ashei)] and southern highbush blueberry (V. darrowi × V. corymbosum) and included analysis of harvest efficiency and fruit quality (percent blue fruit, percent bloom, percent split skin, and internal bruise damage). Six-year-old, 6- to 8-ft-tall ‘Brightwell’ and ‘Powderblue’ rabbiteye blueberry plants were winter pruned to remove vertically growing and overarching canes in the center of the bush in Jan. 2004 and Feb. 2005 respectively. Three-year-old, 3- to 5-ft-tall ‘FL 86-19’ and ‘Star’ southern highbush blueberry plants were similarly pruned in summer (June 2004) or in winter (Feb. 2005). Pruning removed an estimated 30% to 50% of the canopy and opened the middle, resulting in V-shaped plants in both rabbiteye and southern highbush blueberries. Yield of winter-pruned ‘Brightwell’ rabbiteye blueberry was lower compared with unpruned plants during both years, but winter-pruned ‘Powderblue’ rabbiteye blueberry plants produced as much as unpruned plants in 2005. In ‘FL 86-19’ southern highbush blueberry, plants that were summer pruned in June 2004 produced as much as unpruned plants in 2005, but plants that were winter pruned in Feb. 2005 had lower yields than unpruned plants in 2005. The V45 harvester caused little cane damage on pruned blueberry plants. In rabbiteye blueberries, internal fruit damage and skin splitting was less in V45-harvested fruit than in fruit harvested by a sway harvester and nearly that of hand-harvested fruit. However, in ‘FL 86-19’ southern highbush blueberry, the V45 harvester detached a lower percentage of blue fruit and excessive amounts of immature and stemmed fruit. These findings suggest that the V45 harvester has the potential to harvest some rabbiteye blueberry cultivars mechanically with fruit quality approaching that of hand-harvested fruit.
were bred by recurrent selection in areas with warm winters. Breeding started with hybrids between northern highbush cultivars and low-chill wild blueberries from the southeastern United States, notably V. darrowi ( Sharpe and Darrow, 1960 ; Sharpe
)] × 37-9. It is likely that 37-9 resulted from selfing of the northern highbush selection US 37. Fla65-28 resulted from a cross of A [Fla4B ( V. darrowi ) × V. virgatum clone #3] × (‘Berkeley’ × Fla4B) × E-22. E-22 is another northern highbush selection
, including V. corymbosum , V. darrowi , and V. ashei . ‘Suziblue’ has an estimated chill requirement of 400 to 450 h (less than 7 °C). It is an early-season southern highbush with large fruit (2.2 to 2.8 g/berry). Berries are medium to light blue in color
complex pedigree containing V. ashei Reade, V. constablaei Gray, V. corymbosum L., and V. darrowi Camp. ‘Summer Sunset™’ ripens around the time of the early-ripening commercial rabbiteye cultivars Climax and Premier. However, the new cultivar
seedling population derived from a cross of MS122 × MS6 made in Beltsville, MD, in 1988 ( Fig. 1 ), and its pedigree shows that it is a complex hybrid involving species including V. corymbosum , V. darrowi , and a small amount of V.virgatum that
%. V. a . = V. ashei (syn. V. virgatum ); V. c. = V. corymbosum; V. d. = V. darrowi; V. e. = V. elliottii ; V. t. = V. tenellum . Fig. 3. Effect of pollinator visitation on ( A ) berry weight and ( B ) seeds per berry for the five species of
parent in interspecific and interploidy crosses. The North Carolina State University breeding program crossed ‘NC 2267’ (a diploid hybrid that is 1/4 V. corymbosum , 3/4 V. darrowi ) with a selection of diploid V. ovatum . Seedling ‘NC 3048’ was the
, ‘Legacy’, which is three-fourths V . corymbosum and one-fourth the southern species V. darrowi Camp, was the least cold hardy at initial evaluation, even less so than ‘Tifblue’ (100% southern species V. ashei ). ‘Legacy’ had an LT 50 of −16 °C