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- Author or Editor: G. J. Galletta x
Abstract
As a first step in determining the phylogeny of the rabbiteye blueberry (Vaccinium ashei Reade), the potential fertility levels among its purported diploid ancestral species. Vaccinium atrococcum (Gray) Heller, Vaccinium caesariense MacKenzie, Vaccinium darrowi Camp, and Vaccinium tenellum Ait., were determined. Differences existed among species in female fertility as determined by total number of seeds and number of potentially viable seeds. The number of seeds per berry was lower than that reported for highbush and rabbiteye blueberry cultivars. No differences were found among species in potential male fertility as indicated by percent stainable pollen. Pollen diameter was not a good criterion for distinguishing species or ploidy levels. Comparison of fertility of diploid species with that of purported polyploid derivatives is suggested as a possible aid in determining phylogeny in Vaccinium. Unreduced pollen grains were detected in only 2 of the 4 species in this study. The average return from heterploid (4n × 2n) crosses was 3 seedlings per 1000 pollinations.
Abstract
Pollen stainability, frequency of unreduced pollen grains, and pollen diameter were examined in 13 species and 4 interspecific hybrids of Vaccinium comprising 3 ploidy levels. Pollen in the tetraploid species was potentially more fertile (as judged by stainability) than in the diploid species. Pollen stainability in the hexaploids was not different from the diploids or tetraploids. Four pollen viability classes (good, fair, poor, and very poor) were established among species. Practically all of the species studied produced unreduced pollen grains. Mean pollen diameter was 11% larger in the tetraploids than in the diploids and 11% larger in the hexaploids than in the tetraploids. The normal pollen diameter ranges for the 3 ploidy levels of Vaccinium were calculated and presented as a possible taxonomic tool.
Genetic, rather than seasonal or environmental differences, appeared to account for the major portion of the interclonal and interspecific variation observed in pollen stainability and in the frequency of unreduced pollen grains.
Frequent irregularities observed were empty pollen grains and granular, unstained pollen, which were assumed to represent early postmeiotic abortions. Meiosis was studied in a representative species of each ploidy level. Pairing and segregation were essentially normal, but a few multivalents or pseudo-multivalents (bivalents secondarily associated) were observed in the hexaploid species.
Abstract
Representative clones of the diploid (2n = 24) members of the subgenus Cyanococcus (true or cluster-fruited blueberries) of Vaccinium, as well as V. crassifolium Andr. (Herpothamnus subgenus) and V. macrocarpon Ait. (Oxycoccus subgenus) were studied cytologically. They were collected from localities ranging from Florida to Nova Scotia and varied markedly in their gross morphology. The length of the total chromosome complement and the ratio of the longest to the shortest chromosome of each clone were determined. While a range of significant differences were demonstrated among clones, these differences were considered to be of minimal importance in species identification. A single idiogram can represent the karyotypes of all of the diploid Cyanococcus species examined. A tentative idiogram of their haploid complement consisted of 2 long and 2 short chromosomes and 8 of intermediate length, one of which was satellited. All had median or submedian centromeres. The karyotypic stability of the diploid Vaccinium species leads to the conclusion that the broad variability in morphology and adaptation which they exhibit has been principally genic in origin.
Abstract
Several blueberry species were successfully intergrafted. A graft combination of particular horticultural promise in North Carolina was highbush blueberry (V. corymbosum L.) scions grafted onto rabbiteye blueberry (V. ashei Reade) rootstocks, which took advantage of the superior soil adaptability and vigor of the rabbiteye species. Spring grafting and midsummer T-budding were the most successful grafting methods. Stock-scion compatibility was very broad; 24 different highbush scions were successfully grafted onto rabbiteye and sparkleberry (V. arboreum Marsh) roots. Delayed incompatibility symptoms were not found 7 to 10 yrs after grafting. Grafted plants produced new sprouts (“suckers”) from the rootstock crown area, which had to be removed annually. Sucker production increased with age, and varied with season and rootstock. Grafted highbush on rabbiteye plants succeeded in growth and fruiting on several soils on which ungrafted highbush plants had previously failed. Yields of grafted plants were average for the scion cultivar, varying with soil type differences and with number of grafts per plant. Blueberry scion cultivars tended to perform better on one or the other of 2 different rootstocks.
The cultivars Allstar, Honeoye, Kent, and Jewel yielded the most successful summer and subsequent spring crops when planted in mid-July from dormant, cold-stored, multiple-crowned, nursery mother plants. Summer fruit sizing during very high temperatures was a problem; fruit number and quality was not. In a second hot year, the same cultivars did not give satisfactory summer crops when planted after late July. The return spring crop was most successful following planting in July rather than August or September, though there was a significant cultivar × planting date interaction for a number of characters. Nursery mother plants were more productive than first daughter plants. `Tristar' outyielded `Seascape' on black poly-mulched beds but not on killed vetch sod beds. `Allstar' runnered freely and produced good crops on three types of raised bed killed sod mulches and on red, blue, and silver-painted black poly raised bed mulches. Compared to the summer-planted, black, poly-mulched standard, `Mohawk' had increased but later yields, when the poly was painted blue, red, or silver, and much later yields, when mulched with recycled paper or wood fiber. The silver and paper treatments depressed fruit size. The wood fiber mulch seems promising for deliberately delaying ripening by lowering soil temperatures under the mulch. Seedling and selection plantings have generally responded favorably to summer planting from potted or “plug” plant stocks on unfumigated soil, thus, shortening the selection and evaluation cycles, with accompanying savings in land, water, fertilizer, and pesticide use.
Abstract
Four methods of inoculation with Verticillium were tested for effectiveness in infecting strawberry plants grown in a greenhouse bench. The most severe and early symptoms were produced with a macerated mycelium root dip inoculum. Effect of inoculum aggressiveness on the extrapolation of plant resistance information is discussed.
Abstract
The cover is a color photograph of a painting of a ‘Tristar’ strawberry plant by Lynda Chandler at the end of the Beltsville 1980 fall harvest season. ‘Tristar’ and its sister cultivar, ‘Tribute’, are new strawberry introductions from the U. S. Department of Agriculture — University of Maryland breeding program (see also p. 792–795 for more details). These cultivars are the first to combine red stele and verticillium resistance from octoploid cultivated strawberry cultivars with a strong, cyclic expression of the everbearing character from a wild selection of octoploid Rocky Mountain strawberry. ‘Tribute’ and ‘Tristar’ are related through a common grandparent to the ‘Brighton’, ‘Hecker’, and ‘Aptos’ day-neutral cultivars recently introduced in California by Bringhurst and Voth.
Abstract
‘Allstar’ is a vigorous and productive Junebearing strawberry (Fragaria × ananassa Duch.) that produces very large, firm fruit of good quality in late midseason. It is the most recent introduction in a series of red stele root rot-resistant cultivars developed in the cooperative strawberry improvement program of the U.S. Department of Agriculture and the University of Maryland. ‘Allstar’ combines multiple-race resistance to red stele incited by Phytopthora fragariae Hickman with resistance to other root and leaf diseases, has unusually broad adaptation within the eastern United States, and performs well under a number of cultural regimes. Its name implies superior performance under diverse soil, climatic and cultural conditions.
Abstract
A 24 or 48 hour soak in gibberellins (GA) did not influence the total germination of open-pollinated rabbiteye blueberry seeds (Vaccinium ashei Reade, cv. Tifblue). GA4+7 at 100-500 ppm stimulated early germination of seeds from the 2nd to 4th week after sowing, with the maximum effect occurring after 3 weeks. The 48-hour, GA4+7, 100 ppm treatment stimulated germination from the 2nd to 5th week after sowing. Stimulation of earlier germination by GA4+7 hastened seedling transplanting by 2 to 4 weeks. Germination of mature seeds (large, filled) was significantly higher than immature (medium-size, filled) or imperfectly (partially-filled) developed seeds. GA4+7 did not increase germination of immature or imperfectly developed seeds.