Vaccinium Species Research Articles

A Bacterial Leaf Spot of Highbush Blueberry Hardwood Cuttings Caused byPseudomonas andropogonis

A leaf spot has been observed for several years on nursery-grown blueberry cuttings throughout southern New Jersey. A bacterium that produced a white-pigmented colony on yeast extract-dextrose-calcium carbonate agar and was nonfluorescent on King's B agar was repeatedly isolated from lesions on diseased leaves collected from various locations. The bacterium was identified as Pseudomonas andropogonis using diagnostic tests, Biolog, and fatty acid analysis. Infiltration of bacterial suspensions at concentrations of 10 6 and 10 8 cells per ml into leaves of 3- to 5-year-old potted plants and 1-year-old hardwood cuttings resulted in the appearance of necrotic lesions similar to leaf spot symptoms observed on plants in the field. The bacterium was reisolated from the necrotic lesions produced by these inoculations. Inoculation of blueberry isolates into cranberry leaves also caused pathogenic responses. This is believed to be the first report of a bacterial leaf spot on Vaccinium species.

Differences in sucrose metabolism relative to accumulation of bird‐deterrent sucrose levels in fruits of wild and domestic Vaccinium species

We examined variability in sucrose levels and metabolism in ripe fruits of wild and domestic Vaccinium species and in developing fruits of cultivated blueberry (V. ashei and V. corymbosum). The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high‐sucrose fruit, which potentially would be less subject to bird predation. Threefold differences in fruit sucrose concentration were found among Vaccinium species, ranging from 19 to 24 mg (g fresh weight)−1 in V. stamineum and V. arboreum to approximately 7 mg (g fresh weight)−1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Hexose levels were similar among species, ranging from 90 to 110 mg (g fresh weight)–1, and glucose and fructose were present in equal amounts. Soluble acid invertase (EC 3.2.1.26) activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose synthase (EC 2.4.1.13) or sucrose phosphate synthase (EC 2.4.1.14) activities, both of which were low for all species studied. Developmental increases in fruit sugar levels of cultivated blueberry followed a pattern similar to that observed in fruit fresh weight accumulation. Hexose concentrations ranged from 6 to 30 mg (g fresh weight)−1 during the first 60 days after anthesis. Between 60 days and fruit ripening (80 days), hexose levels rose from 30 to 80 mg (g fresh weight)−1. Sucrose was not detected in fruits until ripening, when low levels were found. Insoluble acid invertase activity was relatively high early in fruit development, decreasing as soluble acid invertase activity increased. Between 60 days and fruit ripening, soluble acid invertase activity increased from 3 to 55 μmol (g fresh weight)–1 h–1. Both sucrose synthase and sucrose phosphate synthase activities were low throughout development. The extent of sucrose accumulation in fruits and the degree of variability for this trait among Vaccinium species support the feasibility of developing high sucrose fruits, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.

Differences in sucrose metabolism relative to accumulation of bird-deterrent sucrose levels in fruits of wild and domestic Vaccinium species

Differences in sucrose metabolism relative to accumulation of bird-deterrent sucrose levels in fruits of wild and domestic Vaccinium species

010 BREEDING BLUEBERRIES WITH ALTERED FLOWER ARCHITECTURE

Genetic variation was surveyed within and among 5 Vaccinium species and several hybrid taxa for 6 aspects of flower size and shape. Sufficient variation was found to allow radical changes in flower architecture through breeding. The goal is a flower that pours pollen directly from the anthers onto the stigma without the assistance of pollinating insects. The flowers of V. elliottii had very short styles (mean in mm 5.3 compared to 10.2 for rabbiteye cultivars and 8.5 for highbush cultivars), and certain short-style recombinants from highbush cultivar × V. elliottii crosses came close to the desired positioning of stigmas relative to anthers. The distance (in mm) from the anther pore to the stigma averaged: V. ashei 2.7; V. corymbosum 2.4; V. darrowi 2.3; and V. elliottii 1.0. Compared to highbush cultivars, rabbiteye cultivars tended to have long corollas and narrow corolla apertures, two features believed to be related to poor honeybee pollination. These features were much more favorable in V. ashei × V. constablaei hybrids, with values averaging close to those for highbush cultivars.

746 PB 102 DIFFERENCES IN SUCROSE METABOLISM RELATIVE TO ACCUMULATION OF BIRD-DETERRENT SUCROSE LEVELS IN FRUIT OF VACCINIUM SPECIES

Variability in sucrose levels and metabolism in ripe fruit of several Vaccinium species were examined. The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high-sucrose fruit, which potentially would be less subject to bird predation. Three-fold differences in fruit sucrose concentration were found among species, ranging from 19 to 24 mg·(g fw)-1 in V. stamineum and V. arboreum to about 7 mg·(g fw)-1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Soluble acid invertase activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose phosphate synthase or sucrose synthase activities, both of which were low for all species studied. The degree of variability in fruit sucrose accumulation among Vaccinium species supports the feasibility of developing high sucrose fruit, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.

057 IN VITRO SCREENING OF WESTERN UNITED STATES VACCINIUM SPECIES FOR pH TOLERANCE

Accessions of Vaccinium species (deliciosum, ovalifolium, membranaceum, parvifolium, scoparium) were evaluated for tolerance to higher pH in the root zone using an in vitro screening procedure. Seeds were germinated on media containing all essential nutrients with nitrogen in the nitrate form at pH 5 and pH 6 and evaluated for 21 weeks. Excess EDTA was used to buffer the micronutrients and pH was buffered by MES and succinic acid. Germination varied among species with V. ovalifolium being highest and V. parvifolium not germinating at all. Mortality was lower at pH 5. At pH 6, V. ovalifolium and V. membranaceum exhibited variation for growth while all other species suffered complete mortality.

The Investigation and Cultivation ofVacciniumSpecies in the Soviet Union

This paper catalogues work in the Soviet Union on selection and breeding of various Vaccinium species and on the attempts underway to develop commercial industries for the highbush blueberry, bog whortlebeny, European and American cranberries, lingonberry, and other wild Vaccinium species.

Floral visitors of Vaccinium species in the High Ardennes, Belgium

Pollination ecology of three Vaccinium species considered primarily adapted to bumblebees (Bombus Latr. spp.) was studied in the High Ardennes, Belgium. Observations and insect collections were conducted in a peaty heath during the period 1988-1990, in the bilberry (V. myrtillus), the cowberry (V. vitis-idaea) and the bog whortleberry (V. uliginosum). Nine bumblebee species were caught on Vaccinium, 95 % of these individuals were queens. They frequently visit the Vaccinium species, especially V. myrtillus. V. vitis-idaea attracted primarily honeybees but was also visited, likewise, V. uliginosum, by a diverse pollinator assemblage (with syrphids, solitary bees, bumblebees).

Improved drought tolerance and root development as components of a scheme to breed blueberries for mineral soil adaptability

Blueberry breeding in North America started at the beginning of the 20th century and present cultivars are adapted to irrigated, high organic, acidic, sandy soils. However, sites meeting these requirements are limited, which has forced breeders to develop germplasm that is adapted to unamended mineral soils. Wild Vaccinium species can be found growing on a number of different soil types under a variety of climatic conditions, which indicates that genetic variability for mineral soil adaptability is present in Vaccinium germplasm. However, for a number of reasons progress in the development of mineral soil-adapted blueberry cultivars has been slow. In this paper a breeding scheme is presented that would allow the user to more efficiently access the variability that exists for mineral soil adaptability. The scheme is composed of two different seedling screening techniques (drought and seedling rooting screen) that are designed to eliminate the less vigorous individuals in a population before field testing. The field environment would be used primarily to evaluate individuals for fruit quality and yield characteristics. In blueberries, both general and specific combining ability can be fully exploited because they are vegetatively propagated which immediately fixes any unique combination of genes.

The taxonomy ofVaccinium sectionHemimyrtillus

In view of their awnless stamens and pseudo-10-loculed berries borne on short racemes several NE Asian species ofVaccinium (includingV. hirtum, V. smallii, V. versicolor, andV. yakushimense) were transferred toVaccinium sectionCyanococcus by Sleumer (1941). Subsequently, however, Stevens (1969) and Vander Kloet (1972, 1981) argued on the basis of further study that these taxa should be transferred instead to sectionHemimyrtillus. Phenetic analyses of data from representatives of sectionsCyanococcus andHemimyrtillus, including NE Asian taxa transferred by Sleumer, demonstrate the distinctness of the two sections and support the assignment of the NE Asian taxa to sectionHemimyrtillus. A revised taxonomic treatment and key to the species ofVaccinium sectionHemimyrtillus is provided.

Salinity and Supplemental Calcium Influence Growth of Rabbiteye and Southern Highbush Blueberry

`Tifblue' and `Brightwell' rabbiteye blueberries (Vaccinium ashei Reade.) were subjected to 0, 25, or 100 mM Na+, as Na2SO4 or NaCl, and 0, 1, 3, or 10 mM supplemental Ca2+, primarily as CaSO4, in an irrigated sand culture in the greenhouse. Additionally, the effect of NaCl on `Sharpblue' southern highbush blueberry (primarily V. corymbosum L.) was examined. For unsalinized plants, fastest growth occurred in plants not receiving supplemental Ca2+. Root and shoot growth were depressed as salinity increased in plants lacking additional Ca2+. With 100 mM Na+ as Na2SO4. `Tifblue' root and shoot dry weight increases were only 37% and 25%, respectively, of the increase of unsalinized controls, while with 100 mM Na+ as NaCl, the corresponding shoot and root dry weight increases were only 38% and 43%, respectively. `Brightwell' plants reacted similarly to `Tifblue' in salinity treatments with Na2SO4 and NaCl, but `Sharpblue' plants were more severely affected by 100 mM NaCl than were the rabbiteye cultivars. In no case did addition of Ca2+ have any ameliorative effect on either the dry weight of roots of plants exposed to 25 or 100 mM NaCl or on the shoot growth of plants exposed to NaCl. The inability of Ca2+ to counter Cl- entry or toxicity may account for the lack of amelioration. In contrast, additional Ca2+ did improve shoot growth of plants exposed to Na2SO4. For `Tifblue' plants supplied with 25 mM Na+ as Na2SO4, growth increased by almost 25% in the presence of 10 mM Ca2+, while for `Tifblue' plants treated with 100 mM Na+ as Na2SO4, growth was more than three times greater in plants supplied with 1 mM Ca than in those not given any Ca2+. Growth increase was primarily due to increased leaf area and number. Low (1 mM) concentrations of Ca2+ were more effective in ameliorating the effects of 100 mM Na+ as Na2SO4 than were 3- and 10-mM Ca2+ supplements, possibly because higher Ca2+ additions lead to metabolic damage in these calcifuge Vaccinium species.

Clonal Plants and Environmental Change: Introduction to the Proceedings and Summary

Clonal growth is an important attribute of many groups of plants and animals (White 1979, Harper et al. 1986). In the plant kingdom, phyla from all evolutionary levels show the capacity for clonal growth. The ability to proliferate vegetatively is found within 10 out of 11 classes of vascular plants and within all seven classes with extant representatives, although rare within the Gymnospermopsida (Mogie and Hutchings 1990), and 69 out of 163 families of vascular plants are able to proliferate vegetatively (Tiffney and Nicklas 1985). The importance of clonal growth in temperate and more northerly ecosystems is apparent when the ground area covered by clonal plants is estimated. In the Arctic, 0.9 x 106 km2 of land is covered by Eriophorum vaginatum (Miller 1982) which is a caespitose clonal plant, where recruitment from seedlings depends on small and large scale disturbances in the vegetation (Gartner et al. 1986). In Britain, the most productive natural/seminatural vegetation is dominated by clonal plants such as Phragmites communes and Pteridium aquilinum (Callaghan et al. 1981), while infertile areas are also dominated by clonal plants such as Calluna vulgaris and Nardus stricta (Bunce and Barr 1988). The area of Britain is 230000 km2 and 19% of this is covered by Britain's ten most extensive species which are all clonal (Table 1; Bunce and Barr 1988). In temperate and boreal forests, clonally proliferating species such as Vaccinium and Empetrum species and Deschampsia flexuosa are also abundant.

The Use of Zeatin to Initiate in Vitro Cultures of Vaccinium Species and Cultivars

Explants of mature pot-grown Vaccinium corybosum L. cultivars were tested for initiation of new shoots using two growing conditions and four cytokinin treatments. Initiation tests with 12 genotypes showed significantly higher rates of new shoot growth on modified woody plant (MWPM) medium with 4 mg zeatin/liter at 25C under low light intensity than on any other treatment. Explants at 25C in light with 10 or 15 mg 2iP/liter initiated at a moderate rate, but significantly lower rates were found for all controls and at 4C in darkness. To determine the utility of zeatin for initiation of diverse genotypes, 96 Vaccinium accessions from the National Clonal Germplasm Repository, representing 22 species and 44 cultivars, were screened using 25C and low light intensity. Initiation rates higher than 60% were achieved for 89 of 96 accessions tested. Chemical name used: N6-[2-isopentenyl] adenine (2iP), 6-[4-hydroxy-3-methylbut-2-enylamino]purine (zeatin).

Phenological variation in fruit characteristics in vertebrate-dispersed plants.

We investigated inter-specific variation in fruit characteristics - fruit size, seed number per fruit, seed weight, nutritional content, fruit persistence, and fruit synchronization - in relation to flowering and fruiting phenology in 34 species of fleshy fruited plants. Except for aspects of fruit synchrony and persistence, the results in general were inconsistent with previous suggestions about adaptive variation in phenologically related fruit traits. The main results were as follows: (1) Late flowering, late fruiting, lengthy development time from flower to fruit, and highly persistent fruits constitute a complex of correlated characteristics among the species. (2) Synchronization of fruiting within individuals increased from early ripening fruits to late ripening fruits. Fruiting synchrony was more pronounced in species with a small crop size than in species with a large fruit crop, whereas synchrony was not significantly related to flowering synchronization, nor to life form. (3) Nitrogen and carbohydrate content of fruit pulp did not vary in relation to phenology, whereas lipid content decreased from early to late ripening fruits. (4) No seasonal trends were found for variation in seed size or seed number per fruit. (5) Interactions with flowering phenology and developmental constraints are important in phenological fruiting patterns. Temporal variation in start of fruiting was partly (36%) explained by variation in flowering time. Seed weight variation explained 17% of variation in development time from flower to fruit. (6) Despite constraints from flowering and seed development, some adaptive adjustment in fruiting phenology is likely to be allowed for among the investigated species. Such an adaptive variation in fruiting phenology was suggested by intra-generic comparisons of Prunus and Vaccinium species.

A field and literature survey, with interpretation, of elemental concentrations in blueberry (Vaccinium angustifolium)

Blueberry species are important for assessment of pollutant impacts in boreal settings because they are effective colonizers of disturbed sites, are tolerant of high levels of certain heavy metals, and are an attractive food for humans. To investigate patterns in its accumulation of elements and to provide background data, the concentrations of Al, B, Ba, Br, Ca, Ce, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Si, Sr, Ti, Zn, and Zr were measured in leaves of Vaccinium angustifolium Ait. collected at 64 sites across much of the species range in Canada. These included both cultivated and natural populations. Ranges for 24 other elements in Vaccinium species have been compiled from the literature. Measurements of site and soil characteristics were made for the 64 sites to investigate their effects on concentrations in leaves. The concentration data were right-skewed, and this has implications for both data analysis and environmental impact assessment. The concentrations of most elements were positively correlated, and this was related to soil organic matter content and other soil properties. Plant concentrations were only weakly related to soil concentrations. Plant height was positively correlated to soil pH and leaf Ca, opposite to the expected trend. Overall, about half of the variation in plant concentrations was related to site-to-site variation; with the exception of Ni and Mg levels around Sudbury, Ontario, there was little indication of spatial grouping. The data indicate a relatively homogeneous elemental composition of V. angustifolium across the range sampled and between cultivated and natural populations. Key words: metals, nutrient, background, impact, pollutant.

POTENTIAL OF SOME INTERSPECIFIC HYBRIDS IN BREEDING SOUTHERN HIGHBUSH BLUEBERRY

Eight clones with various Vaccinium species in their background were evaluated to determine their potential for improving fruit characteristics in the southern highbush blueberry. One clone was crossed with each of the others to produce seven sets of progenies which were evaluated with the parent clones. Heritability estimates were computed as the regression of progeny on parental means for each character. The progenies ranged from small to average berry size and weight, were above average for picking scar, and were generally less than average for color, firmness, and flavor. Mean of progenies was not significantly different from the parental mean for any character. Very high (0.45-0.85) heritability estimates were found for each character except berry firmness (0.22). These results suggest that considerable improvement in each character except possibly berry firmness should result from phenotypic recurrent selection in a broad based population involving these parents.

VESICULAR‐ARBUSCULAR MYCORRHIZAE IN HAWAIIAN ERICALES

Vesicular‐arbuscular mycorrhizae (VAM) are reported for the first time in four species of Hawaiian Ericales, Vaccinium calycinum, V. dentatum, and V. reticulatum of the Ericaceae and Styphelia tameiameiae of the Epacridaceae. The coarse roots (> 1.5 mm diam) of many specimens were densely colonized by VAM fungi, with up to 90% of the length of roots containing arbuscules, vesicles, coils, and internal hyphae. Spores of an undescribed Glomus sp. were associated with two species of Vaccinium. The hair roots of all species bore the ericoid mycorrhizae typical of certain families of this order. The high frequency of VAM in Hawaiian populations of Ericales suggests that ancestral Ericales possessed the capacity to form both VA and ericoid mycorrhizae. An evolutionary sequence of mycorrhizal dependency in the Ericales is presented.

Benzoylglucoses from two Vaccinium species

1- O-Benzoyl-β- d-glucose (main component), 2- O-benzoyl-β- d-glucose, 6- O-benzoyl-α- d-glucose, and 6- O-benzoyl-β- d-glucose were isolated, identified and quantified from red whortleberries and cranberries.

Stem anatomy of Vaccinium section Cyanococcus and related taxa

Twenty-nine Vaccinium species were scored for 14 stem and twig characters to determine whether or not vegetative features would support current taxonomic delimitations within the genus. The data obtained show not only that the verrucose characteristic of the twigs, one of the character states that defines Vaccinium section Cyanococcus, is caused by the presence of raised stomata, but also that members of this section have a peculiar mode of periderm development. In addition to the type of periderm development, the occurrence of lignification in twigs and stems was also noted, but was found not to be taxonomically useful at the sectional rank.

Flooding Responses of Vaccinium Species

Abstract Flooding damage causes millions of dollars in losses to horticultural crops every year. Plantings established on sites with poor drainage and/or an impervious soil layer may flood periodically after heavy rainfall or excessive irrigation. Planting sites with lowlying areas or where site preparation is inadequate for drainage of excess water add to the problem. Poor soil aeration associated with flooding may induce numerous soil and plant changes that adversely affect plant survival, growth, development, and yield. Organic and inorganic soil toxins may accumulate in flooded soils, adversely affecting plant metabolism and physiology.