James R. Ballington
Own-rooted `Premier' blueberry (V. ashei Reade) was compared to `Premier' grafted on V. arboreum Marsh. (sparkleberry) for yield and fruit characteristics in a five-rep RCB design with three plants/rep. With grafted plants, three reps were on rootstock #17 and two on rootstock #10, and results were combined for statistical analyses. Production of suckers by rootstocks was also recorded. Plants wereestablished on an upland doughty mineral Fuquay soil, modified with sawdust, at Jackson Springs, N.C. Supplemental irrigation was applied only in the establishment year and the following year, and landscape fabric was installed in the rows for weed control also in the year following establishment. `Premier' grafted on V. arboreum yielded significantly higher than own-rooted `Premier' in all three harvest seasons. Fruit size on grafted plants was also significantly larger than on own-rooted plants in harvest years 2 and 3. There were no differences in fruit color, picking scar, firmness, or flavor in years 2 and 3, and only small differences in harvest year 1. The data for years 2 and 3 indicated that there were differences among stocks in yield; however, both graft combinations were higher-yielding than own-rooted plants. There were also differences among stock clones for the number of suckers produced in harvest years 2 and 3. The highest-yielding graft combination also had the lowest number of rootstock suckers.
James R. Ballington
Public funding for land-grant university plant breeding programs has declined to the point that alternative sources of funding have had to be identified in order for these programs to continue. Small fruit breeding programs at land-grant universities in the southern region of the U.S. now derive their support for day to day operations from a number of alternative funding sources including commodity organizations and research foundations. Royalty income generated from sale of plants of patented cultivars has also become a significant source of support for essentially all land grant programs. In addition, cooperative agreements and contracts with partners in private industry play a prominent role in support for several programs, and these will likely increase significantly in the near future. At present, U.S. plant patents are generally applied for upon the release of cultivars from small fruit breeding programs at land grant universities in the southern region, with some move toward trademarking. Releases are generally nonexclusive within the region, and either exclusive or nonexclusive outside the region. The use of germplasm from other breeding programs usually carries with it the expectation of mutual exchange and use of germplasm and/or sharing of royalty income from cultivars derived from such germplasm.
Gustavo Giménez and James R. Ballington
Two half diallel mating designs were conducted to study the inheritance of resistance to Colletotrichum acutatum Simmonds on runners of strawberry. The main design included six genotypes representing a range of responses to the pathogen: `Chandler' (very susceptible); FL 87-210 (tolerant); MS/US 541 (very resistant); NC 92-01 (Fragaria chiloensis Duch.) (resistant); NCH 87-10 (tolerant-susceptible); and NCC 89-39 (susceptible). The cross `Chandler' × MS/US 541 was absent. The secondary test included `Chandler' and selections FL 87-210 and NC 85-01 (Fragaria virginiana Duch.) (very resistant) as parents. Griffing's methods 4 and 2, model I, were used to test for combining ability in the main and secondary tests, respectively. General combining ability and specific combining ability were highly significant in all analyses. This study indicated that nonadditive effects are more important than additive effects in the inheritance of resistance of runners to anthracnose. The frequency distribution of lesion lengths within progenies suggests that resistance to C. acutatum on runners is quantitative. Therefore, breeding for resistance should be accomplished using progeny testing followed by individual selection within progenies.
N. Vorsa and James R. Ballington
Eight highbush blueberry (V. corymbosum L.) triploids (2n = 3x = 36) were crossed with diploids (2n = 2x = 24), tetraploids (2n = 4x = 48), and hexaploids (2n = 6x = 72). No plants were recovered from 4021 3x × 2x crosses. One triploid was relatively fertile in 3x × 4x and 3x × 6x crosses, which is most likely attributable to 2n gamete production in the triploid. The lack of fertility of triploids, which do not produce 2n gametes, in crosses with diploids and tetraploids suggests that the production of gametes with numerically balanced (n = 12 or 24) chromosome numbers is extremely low. In addition, the inability to recover progeny from 3x × 2x crosses also suggests that aneuploid gametophytes and/or zygotes, including trisomics, are inviable in blueberry. Pollen stainability was also highly reduced in triploids. Frequency distributions of anaphase I pole chromosomal constitutions of three triploids were significantly different from one another. Two of the three distributions were shifted toward the basic chromosome number of 12, with one triploid having 25% poles with 12 chromosomes. However, the sterility of 3x × 2x and 2x × 3x crosses indicates that lagging chromosomes during meiotic anaphases are probably not excluded from gametes, resulting in unbalanced gametes in blueberry. Triploids can be used as a bridge to facilitate gene transfer from the diploid and tetraploid levels to the hexaploid level in blueberry.
James R. Ballington and Susan D. Rooks
Three rabbiteye blueberry selections, NC 1550, NC 1877, and NC 2305, will be released by the North Carolina Agricultural Research Service in Spring 1997. All three selections are self-fruitful, with fruit as large or larger than Tifblue, with good picking scars, aromatic flavor, and resistance to fruit cracking. NC 1877 is early-blooming and ripens a few days later than Premier, with similar color, firmness, and quality. Plants of NC 1877 are semi-upright and of only moderate vigor. Both NC 1877 and NC 1550 are resistant to the sharpnosed leafhopper which transmits blueberry stunt. NC 1550 blooms with or slightly later than Tifblue and is outstanding for consistent productivity, particularly on spring frost—prone sites. It ripens in early midseason to midseason, usually a few days ahead of Tifblue. Stemming was a problem in one year on overcropped plants. NC 1550 and NC 2305 have average to above color, and fruit firmness equal to Tifblue. NC 2305 blooms and ripens with Tifblue in most years. Fruit quality is at least equal to Premier and it fruits primarily on the tips of the branches. The names of these selections are Ira' (NC 1550), 'Montgomery' (NC 1877), and 'Yadkin' (NC 2305).
James R. Ballington and Barbara J. Smith
Thirty-three accessions of Fragaria virginiana collected from Mississippi in 1995 were evaluated for horticultural traits and leaf disease resistance at Reidsville, N.C., and strawberry anthracnose resistance (Colletotrichum acutatum and C. fragariae) at Poplarville, Miss., in 1997. The range of variability in berry shape, fruit flesh color, fruit skin toughness, and degree of sunkenness of seeds among accessions indicated probable introgression with F. xananassa in most all accessions. Seventeen of 29 accessions screened for resistance to C. acutatum were resistant, and an additional 10 were tolerant. Overall, these accessions appear to be good additional sources of resistance to this, the prevalent species of anthracnose in the southeastern United States. In addition, the majority of accessions appear to be tolerant-resistant to leaf scorch, leaf blight, and/or powdery mildew. Nine accessions were resistant to all three leaf diseases, and four were resistant to C. acutatum as well as the three foliar diseases. No accessions were resistant to C. fragariae and only five were tolerant. All five accessions tolerant to C. fragariae were also either resistant or tolerant to C. acutatum but the converse was not true.
James R. Ballington, Barclay Poling, and Kerry Olive
Until recent years, there have been few attempts in the midsouth to evaluate alternative types of strawberries (e.g., day-neutrals); alternative cultural systems (e.g., tunnel culture); or specific products (e.g., rowcovers) that could be used for either season extension and/or off-season production. In the early 2000s, research was undertaken to evaluate day-neutral (DN) strawberry production in higher elevations in western North Carolina for harvest in the summer and fall. The effect of DN cultivar, plastic mulch color, planting dates, and plant types was studied in at the Upper Mountain Research Station, Laurel Springs, NC (elevation 914 m) over several seasons. In the 2004 season, the DN ‘Everest’ had yields of nearly 1 kg/plant on white plastic mulch using plugs transplanted in late Sept. 2003. However, ≈95% of ‘Everest's’ production occurred in July and August, when U.S. strawberry prices to growers in wholesale fresh markets have averaged $1.32 and $1.68 kg, respectively (2001 to 2005). Assuming a production level of ≈1 kg/plant, market prices above $2.48 kg (breakeven cost) will be needed to make day-neutral strawberry production in the southern Appalachians a profitable venture. We observed peak periods of heavy production in midsummer and more research is needed to identify cultural strategies with plastic mulches, plant types, and possibly rowcovers to increase fall fruit volumes.
Gina E. Fernandez and James R. Ballington
Yield performance of primocane-fruiting experimental blackberry (Rubus spp.) cultivars from two breeding programs were evaluated in the southern Appalachian Mountains. The trial consisted of the nine experimental cultivars: NC 533, NC 534, NC 535, NC 537, NC 538, NC 539, APF-27, APF-46, and Prime-Jim®. In addition, rowcovers were applied to split plots in the spring to determine if harvest dates could be advanced. In 2007, five experimental cultivars had comparable high total yields (APF-27, APF-46, NC 535, NC 537, and NC 539), yet only three of these had comparable marketable yields (APF 27, APF-46, and NC 537). In 2008, APF-27 and APF-46 had significantly higher total yield (2234.5 and 2257.3 g/plant, respectively) and marketable yield (1611.2 and 1654.2 g/plant, respectively) than all other experimental cultivars. Rowcover treatments did not increase or decrease either total or marketable yield in any of the experimental cultivars in either year. In addition, rowcovers did not advance the date of 5% or 50% harvest in either year. On the basis of the conditions imposed in these studies, we determined that “APF” selections evaluated in this trial have higher second-year yield than “NC” selections, primocane-fruiting experimental cultivar yields are lower than yields commonly found with floricane-fruiting blackberries, and rowcovers as applied in this study are not a viable option for advancing harvest season of primocane-fruiting blackberries in the southern Appalachian Mountains.