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- Author or Editor: Gene J. Galletta x
This review briefly summarizes the status of the Southern strawberry industries during the 20th century. Objectives, contributions, and personnel of the Southern state and federal improvement programs are presented. The future of the southern strawberry industries and their reduced number of breeding programs are predicted, with emphasis on the objectives which may have to be altered to accommodate new and continuing problems.
Bacterial angular leafspot disease (BALD) of strawberry, caused by Xanthomonas fragariae, a slow-growing and often difficult pathogen to isolate from infected plants, is most commonly manifested as small discrete, angular, translucent lesions on leaves and sepals. As the bacteria infect systemically, plants may wilt and die. BALD has become increasingly important in North America and other strawberry-growing areas of the world. The systemic nature of the pathogen also is cause for concern with international shipment of strawberry plants, especially because there is no practical method for determining the presence of the bacteria in symptomless, infected plants, nor is there a practical method of chemical control. All cultivars of Fragaria × ananassa (8×) are susceptible to BALD, although a range of susceptibility is often apparent in plantings. Resistant genotypes have been reported among clones of F. virginiana (8×), F. moschata (6×), and F. vesca (2×). A program has been initiated to evaluate native octoploid and diploid strawberry germplasm for resistance to BALD.
The effect of silicon (Si) foliar applications on metabolic changes and powdery mildew infection in strawberry plants were determined. Silicon was used in the forms of potassium (K) and sodium (Na) salts. Foliar sprays containing 0, 250, 500, 750, and 1000 ppm of Si were applied. Strawberry plants showed no difference in response to the K or Na salts of Si during the seven weeks of experimental period. Plants treated with potassium and sodium silicate showed reduced severity of powdery mildew, increased chlorophyll content, and increased plant growth. Potassium and sodium silicate treatments also induced metabolic changes such as an increase in citric acid and malic acid levels, and a decrease in fructose, glucose, sucrose, and myoinositol content. The treated tissues also had higher ratios of (18:2 + 18:3)/18:1 in glycolipids and phospholipids and elevated amounts of membrane lipids in leaves and petioles. These results suggest that Si has beneficial effects on strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.
Abstract
Fourteen highbush blueberry cultivars and selections differed greatly in percentage blue and green fruit removed during a 3 second vibration of individual fruiting shoots with a hand-held vibrator. With cultivars ‘Croatan’, ‘Wolcott’, ‘Morrow’, ‘Murphy’, and ‘Collins’ more than 90% of the blue fruit and less than 15% green fruit were removed. These cultivars have desirable detachment characteristics and required a force of less than 85 g to remove individual blue fruit.
Abstract
Variation in vegetative and reproductive growth patterns leading to summer flowering and fruiting was evaluated in everbearing and in representative Junebearing strawberry (Fragaria × ananassa Duch) clones under simulated summer conditions in the greenhouse and in growth chambers. Summer flowering intensity, periodicity, fruit set, and maturation were related to plant architectural parameters such as crown, leaf and runner production, number of meristems produced and differentiated, leaf areas and petiole length, plant volume, and dry weight allocation patterns. A continuum of growth habits and flowering behavior precluded rigid classification of summer flowering response, but useful arbitrary distinctions were made on the bases of: photoperiod reaction into short-day (Junebearing) vs. weak, intermediate, or strong day-neutrals; or summer fruit expectation into essentially none (Junebearing) vs. sporadic or consistent everbearers. Critical criteria for separating Junebearers from everbearers include degree of summer flowering and fruiting (fresh or dry weight basis), plant volume (and its components, petiole length, and average leaf area), and the dry weight allocation ratios—root : shoot and reproductive : vegetative. Everbearing (or day-neutral) types could be distinguished by plant volume and composition differences (size, number, and percentage of developed meristems, leaf area ratio, reproductive dry weight, etc.) and continuity of individual plant flowering. Three basic models of shoot growth and inflorescence positioning are proposed from evidence for alternative modes of flowering site generation in everbearing strawberries.
Abstract
The comparative self-compatibility, intra-, and interspecific crossability of representative clones of V. atrococcum (Gray) Heller, V. caesariense Mackenzie, V. darrowi Camp, and V. tenellum Aiton was determined. The number of germinated seeds and number of vigorous seedlings proved to be the best criteria for evaluation of crossability. The 4 species were largely self-incompatible. Generally, intraspecific and interspecific crossability levels were singificantly higher than those of the self-pollinations. Interspecific crossability was significantly lower than intraspecific crossability. Crossability levels within species and the range in crossability in individual combinations among species were extremely variable. Although F1 hybrids were produced in each of the 6 species hybridizations attempted, the rate of success was highly variable, and the direction in which the cross was made was usually critical. Specific combining ability was considerably more important than general combining ability in achieving species hybridizations. The hypothesis of complete homoploid interfertility in Vaccinium was not valid for these 4 species. The ranking of species crossability (number of vigorous seedlings per 100 pollinations) from highest to lowest was: V. atrococcum – V. caesariense, V. atrococcum – V. darrowi, V. darrowi – V. tenellum, V. caesariense – V. tenellum, V. caesariense – V. darrowi, and V. atrococcum – V. tenellum.
Abstract
Tissue culture-propagated (TC) strawberry plants (Fragaria × ananassa Duch.) had a cultivar-dependent shift in susceptibility to Phytophthora fragariae Hickman and Verticillium albo-atrum Reinke and Berthold root-rotting fungi. TC-propagated ‘Tribute’, a resistant cultivar, had a disease reaction similar to that of runner-propagated ‘Tribute’ plants. TC-propagated and juvenile selfed seedlings of ‘Raritan’, a susceptible cultivar, were more susceptible to these diseases than ‘Raritan’ runner plants. The TC plant disease reaction shifted toward the runner plant (or usual clonal) reaction with increasing time out of in vitro culture.
Abstract
‘Tribute’ and ‘Tristar’ are everbearing strawberry cultivars (Fragaria × ananassa Duch.) that fruit in spring, summer, and fall (as indicated by the prefix “Tri-”). They are the first everbearing strawberries bred for culture in the eastern United States which combine resistance to red stele root rot, incited by Phytophthora fragariae Hickman, with a high degree of tolerance to verticillium wilt, incited by Verticillium albo-atrum Reincke & Berth. Their generally consistent good health, productivity, and fruit quality under a number of cultural systems suggest that these cultivars will offer new opportunities to the strawberry home gardener and commercial grower alike.