Velvet Leaf Blueberry Research Articles

Inoculation with Ericoid Mycorrhizal Associations Alleviates Drought Stress in Lowland and Upland Velvetleaf Blueberry (Vaccinium myrtilloides) Seedlings.

Although velvetleaf blueberry (Vaccinium myrtilloides) is usually associated with sandy (upland) areas of the North American boreal forest, lowland populations can be also found in bogs, suggesting possible adaptations to different site conditions. In this study, we examined the role of ericoid mycorrhizal (ERM) fungi in conferring drought resistance to the upland and lowland velvetleaf blueberry seedlings. The seedlings were inoculated with four ERM fungi (Pezicula ericae, Pezoloma ericae, Meliniomyces variabilis, and Oidiodendron maius) isolated from the roots of ericaceous plants and grown under controlled environmental conditions in sterilized soil. The inoculated and non-inoculated (inoculation control) plants were subsequently subjected to three cycles of drought stress by withdrawing watering. Lowland plants appeared to benefit relatively more from mycorrhizal colonization, compared with the upland plants, in terms of plant growth and drought survival. After three weeks of treatments, the dry weights of non-inoculated well-watered upland plants were higher compared to the non-inoculated lowland plants. However, these differences were offset by the inoculation of plants with ERM fungi, some of which also significantly improved drought resistance characteristics of the upland and lowland plants. There were no major differences in the effects of different ERM fungal species on drought responses of upland and lowland plants. Of the examined ericoid mycorrhizal fungi, inoculation with Pezicula ericae was the most effective in conferring drought resistance characteristics to both upland and lowland seedlings and helped maintain higher shoot water potentials, net photosynthetic, and transpiration rates in plants subjected to drought stress.

Impact of soil stockpiling on ericoid mycorrhizal colonization and growth of velvetleaf blueberry (Vaccinium myrtilloides) and Labrador tea (Ledum groenlandicum)

Soil stockpiling is a common practice prior to the reclamation of surface mines. In this study, velvetleaf blueberry and Labrador tea plants were grown from seed in fresh soil, stockpiled soil (1 year), and autoclaved stockpiled soil (1 year) obtained from the Canadian boreal forest. After 7 months of growth, the root colonization intensity with ericoid mycorrhizal (ERM) fungi in both plants growing in stockpiled soil was lower compared to plants growing in the fresh soil. The diversity of ERM fungal species in roots also decreased due to soil stockpiling and Pezoloma ericae was absent from the plants growing in stockpiled soil. Changes in the ERM root colonization in plants growing in stockpiled soil were accompanied by decreases in root and shoot dry weights. Leaf chlorophyll, nitrogen, and phosphorus concentrations of velvetleaf blueberry were higher in fresh soil compared to 1‐year stockpiled soil. Plants grown in the autoclaved stockpiled soil became colonized by the thermotolerant ERM fungus Leohumicola verrucosa and showed higher root and shoot biomass compared to the nonautoclaved stockpiled soil. The results point to the importance of ERM fungi for growth of ericaceous plants, even under favorable environmental conditions and adequate fertilization, and suggest that reduced ERM colonization intensity and ERM fungal diversity in roots likely contributed to the negative effects of soil stockpiling on growth of velvetleaf blueberry and Labrador tea.

Predicting Occurrence, Abundance, and Fruiting of a Cultural Keystone Species to Inform Landscape Values and Priority Sites for Habitat Enhancements

Environmental niche modeling is an increasingly common tool in conservation and management of non-timber species. In particular, models of species’ habitats have been aided by new advances in remote sensing and it is now possible to relate forest structure variables to understory species at a relatively high resolution over large spatial scales. Here, we model landscape responses for a culturally-valued keystone shrub, velvet-leaf blueberry (Vaccinium myrtilloides Michaux), in northeast Alberta, Canada, to better understand the environmental factors promoting or limiting its occurrence, abundance, and fruit production, and to guide regional planning. Occurrence and abundance were measured at 845 and 335 sites, respectively, with both strongly related to land cover type and topo-edaphic factors. However, their influence varied widely, reflecting differences in the processes affecting occurrence and abundance. We then used airborne laser scanning (ALS) to characterize horizontal forest canopy cover for the study area, and related this and other geospatial variables to patterns in fruit production where we demonstrated a five-fold increase in fruit production from closed to open forest stands. We then simulated forest canopy thinning across the study area to identify places where gains in fruit production would be greatest following natural disturbance or directed management (e.g., thinning, prescribed burning). Finally, we suggest this approach could be used to identify sites for habitat enhancements to offset direct (land use change) or indirect (access) losses of resources in areas impacted with resource extraction activities, or simply to increase a culturally-valued resource through management.

Ericoid mycorrhizal fungi enhance salt tolerance in ericaceous plants.

To examine the effects of ericoid mycorrhizal (ERM) fungi on salt tolerance of ericaceous plants, we inoculated roots of velvetleaf blueberry (Vaccinium myrtilloides), Labrador tea (Rhododendron groenlandicum), and lingonberry (Vaccinium vitis-idaea) with ericoid mycorrhizal fungi Oidiodendron maius and Meliniomyces variabilis. Plants were subjected to 0 (NaCl control) and 30mM NaCl treatments, and plant dry weights, gas exchange, and leaf chlorophyll concentrations were compared in inoculated and non-inoculated plants. M. variabilis increased root dry weights in all three species of NaCl-treated plants, and O. maius enhanced root dry weights of lingonberry plants treated with NaCl. Both fungal species were especially effective in enhancing root and shoot dry weights in control (0mM NaCl) and NaCl-treated lingonberry seedlings. Leaf chlorophyll concentrations were enhanced by fungal inoculation in all three plant species, and this effect persisted under salt stress in Labrador tea and lingonberry. Salt treatment drastically reduced transpiration rates (E) and lowered net photosynthesis (Pn) to the negative values in all three species of non-inoculated plants, and this effect was partly or almost completely reversed by the inoculation with O. maius and M. variabilis. Fungal inoculation was especially effective in reducing NaCl effects on Pn in lingonberry. Oidiodendron maius and M. variabilis were also equally effective in reversing NaCl-induced declines of E in velvetleaf blueberry and lingonberry. However, in Labrador tea, O. maius reversed the decline of E in NaCl-treated plants less compared with M. variabilis resulting in high photosynthetic water use efficiency values. The results support the hypothesis that, similarly to arbuscular mycorrhizal and ectomycorrhizal associations, ERM association increases salt tolerance of plants.

Effects of Linear Disturbances and Fire Severity on Velvet Leaf Blueberry Abundance, Vigor, and Berry Production in Recently Burned Jack Pine Forests

There is limited information on how velvet leaf blueberry (Vaccinium myrtilloides Michx.) responds to fires and existing small forest gaps associated with narrow linear disturbances. We measured the effects of narrow forest linear gaps from seismic lines used for oil and gas exploration versus adjacent (control) forests across a fire severity (% tree mortality) gradient on the presence, abundance (cover), vigor (height), and berry production of Vaccinium myrtilloides in recently (five-year) burned jack pine (Pinus banksiana Lamb.) forests near Fort McMurray, Alberta. Presence was greatest in forests that experienced low to moderately-high fire severities with declines at high fire severity. Abundance did not differ among seismic lines or adjacent forest, nor did it differ along a fire severity gradient. In contrast, vigor and berry production were greater on seismic lines compared to adjacent forests with fire severity positively affecting berry production, but not plant vigor. After controlling for changes in plant cover and vigor, berry production still increased with fire severity and within seismic lines compared with adjacent forests. Our findings suggest that narrow gaps from linear disturbances and fire severity interact to affect the fecundity (berry production) and growth (height) of Vaccinium myrtilloides. This has important implications for assessing the ecological effects of fire on linear disturbances associated with energy exploration in the western boreal forest.

Propagation of Vaccinium membranaceum and V. myrtilloides: Seeds, Hardwood Stem, and Rhizome Cutting Methods

Propagation trials were completed using seeds, hardwood stem cuttings, and rhizome cuttings from black huckleberry ( Vaccinium membranaceum Douglas ex Torr. [Ericaceae]) and velvetleaf blueberry ( V. myrtilloides Michx. [Ericaceae]) growing in central British Columbia, Canada. Seed germination success rates for V. membranaceum were 26.0% in 2006, 4.7% in 2007, and 66.0% in 2008, compared with 14.7% in 2006, 13.0% in 2007, and 28.5% in 2008 for V. myrtilloides . Germination rates for seeds sown directly after extraction from fresh berries were similar to those that had been air-dried for 48 h, and those stored for 1 y. Germination rates did vary significantly between Vaccinium species and among different years. Hardwood stem cuttings of both V. membranaceum and V. myrtilloides , taken in February, had low rooting rates (2.5%). Rooting hormone formulation, rooting substrate, and bottom heat failed to influence rooting success. Rhizome cuttings of V. myrtilloides had an 85% success rate, compared to 70% for V. membranaceum . Bottom heat significantly reduced the success rate of rhizome cuttings, whereas rooting substrate had no significant influence. Mass production of either V. membranaceum or V. myrtilloides plants was easiest by using seedlings grown from seeds; however, if clonal plants are desired (or a short production time required), rhizome cuttings might be the best option, rather than hardwood stem cuttings.

Bud-autogamy in the velvet-leaf blueberry, Vaccinium myrtilloides Michx.

In velvet-leaf blueberry, Vaccinium myrtilloides Michx., flower buds at different stages of development were collected from managed, lowbush blueberry populations and examined microscopically for evidence of autodeposition of selfpollen. During late bud development, anther pores opened for pollen tetrad release and remained relatively close to the stigma. Just prior to full bloom, at petal separation, 18% of the flower buds were pollinated. Self-pollination prior to anthesis may either ensure some reproductive success or enhance the seed set from subsequent cross pollinations. Key words: Vaccinium, autogamy, self-pollination

Structural characteristics of root–fungal interactions for five ericaceous species in eastern Canada

A combination of light microscopy (including differential interference contrast) and laser scanning confocal microscopy was used to document the colonization patterns of epidermal cells and details of intracellular hyphal complexes of five native ericaceous hosts: Vaccinium oxycoccos L. (bog cranberry), Ledum groenlandicum Oeder. (Labrador tea), Vaccinium myrtilloides L. (velvet-leaf blueberry), Kalmia angustifolia L. (sheep laurel), and Gaultheria procumbens L. (wintergreen). Colonization patterns, hyphal complex morphology, and the structure of thick-walled epidermal cells varied considerably among hosts. Multiple hyphal connections were observed between adjacent epidermal cells, indicating that one fungal entry point may result in the colonization of more than one epidermal cell. Further field observations combined with fungal isolations from field-collected plants, identification, and reinoculation studies of other species in the large Ericaceae family are required to determine the full range of structural details in ericoid mycorrhizas.Key words: ericoid mycorrhizas, hair roots, intracellular hyphal complexes, confocal microscopy.

Effect of Fire Intensity and Depth of Burn on Lowbush Blueberry, <em>Vaccinium angustifolium</em>, and Velvet Leaf Blueberry, <em>Vaccinium myrtilloides</em>, Production in Eastern Ontario

The effects of prescribed fire intensity and depth of burn were investigated on Lowbush Blueberry (Vaccinium angustifolium) and Velvet Leaf Blueberry (Vaccinium myrtilloides) stem density, blueberry production and the number of blueberries/stem in a clear-cut Jack Pine, Pinus banksiana, ecosystem of eastern Ontario. Blueberry production and stem density were significantly (P < 0.001) increased by low intensity prescribed fires of 597 and 1268 kW/m. In contrast, prescribed fires of medium and high intensities did not affect blueberry production and stem density. The number of blueberries/stem was not affected (P = 0.056) by prescribed burning, two years after treatment. Pearson's multiple correlation analysis showed that blueberry production (R: -0.683, P < 0.01), stem density (R: 0.733, P < 0.01) and the number of blueberries/stem (R: 0.803, P < 0.01) correlated with depth of burn. As well, blueberry production (R: 0.507, P < 0.05) and stem density (R: -0.504, P < 0.05) correlated with fire intensity. Depth of burn was a better predictor of berry production and stem density than fire intensity. These results suggest that only low intensity fires with little penetrating effect in the ground should be used to manage blueberry crops.

Morphological plasticity and regeneration strategies of velvet leaf blueberry ( Vaccinium myrtilloides Michx.) following canopy disturbance in boreal mixedwood forests

The effects of canopy disturbance on the abundance, growth, morphological plasticity, biomass allocation and fruit production of velvet leaf blueberry ( Vaccinium myrtilloides Michx.) were examined in 1996 in a second-growth boreal mixedwood forest near Nipigon, northwestern Ontario that had been logged by either shelterwood cutting or clearcutting in 1993. We found that V. myrtilloides was able to persist in both open and closed canopy boreal mixedwood forests managed for commercial timber extraction. Persistence under heavy shade conditions was accompanied by significant morphological and biomass allocation plasticity. Specific leaf area, leaf area, individual leaf weight, and the proportion of total biomass in stems and foliage changed along an understory light gradient from 0% to 67% percent photosynthetic photon flux density (% PPFD). The degree of above-ground morphological plasticity may explain blueberry's ability to survive under low light conditions. Reproductive performance of V. myrtilloides was greatest under the partial shade conditions associated with shelterwood cutting. Blueberry bushes growing in clearcuts overgrown with 3-year old aspen ( Populous tremuloides Michx.) saplings remained mostly vegetative whereas the number, fresh weight and dry weight of berries in shelterwood cuts was 94% grater than that produced after clearcutting. We attributed the lower fruit yields in the clearcuts to heavy shading from regenerating hardwoods, and mechanical damage to above-ground biomass. The paucity of seedling regeneration as well as extensive mechanical damage to above-ground stems by logging equipment delayed vegetative regeneration of V. myrtilloides in large canopy openings of the clearcut blocks. Unlike other more aggressive ericaceous species (e.g. Kalmia angustifolia var. angustifolia L., Gaultheria shallon Pursh.), V. myrtilloides was unable to resist invasion from faster growing hardwood species (e.g. P. tremuloides) and was rapidly overtopped. V. myrtilloides plants in the uncut control blocks received 3.9% of full sunlight, whereas those growing in the partial cut and clearcut blocks received an average of 25.3% and 32.5% PPFD, respectively. Cover of vegetation over-topping blueberry plants was highest in the uncut forest (90.3%), but was not significantly different between the partial cut (45.5%) and clearcut (50.1%) treatment blocks.

Phenology of Vaccinium spp. in a black spruce (Picea mariana) plantation in northwestern Ontario: possible implications for the timing of forest herbicide treatments

This study reports on the phenology of 180 vegetative and 180 reproductive shoots of lowbush blueberry (Vaccinium angustifolium Ait.) and velvet leaf blueberry (Vaccinium myrtilloides Michx.) in a young black spruce (Picea mariana (Mill.) BSP) plantation near Thunder Bay, northwestern Ontario. Leaves of both species emerged in mid-May and remained uniformly green until mid-August. By late August, the majority of tagged shoots had turned red and were beginning to deteriorate. Approximately 30% of tagged shoots lost their leaves by 25 September in both V. angustifolium and V. myrtilloides. Patterns of leaf development in V. angustifolium and V. myrtilloides suggest that Vaccinium spp. may be less susceptible to foliar-applied herbicides if applications are made during or following the period of leaf senescence (i.e., between late August and late September). However, delayed treatment may be impractical in conifer plantations, since the time of leaf senescence and abscission of blueberry coincides with that of many target species.

Effects of conifer release treatments on the growth and fruit production of Vaccinium spp. in northwestern Ontario

Berry production and vegetative recovery of lowbush blueberry (Vaccinium angustifolium Ait.) and velvet leaf blueberry (Vaccinium myrtilloides Michx.) were documented for three growing seasons (1994, 1995, 1996) after brushsaw, single operational and multiple nonoperational Vision® herbicide (active ingredient glyphosate), and control treatments in a jack pine (Pinus banksiana Lamb.) plantation in northwestern Ontario. Vaccinium angustifolium fruit production was significantly (P <= 0.05) reduced by both the single and multiple treatments in all 3 years of the study. Fruit production by V. myrtilloides was significantly (P <= 0.05) reduced only by the multiple treatment. The significant reduction in berry production by V. angustifolium contributed to an overall drop in the availability of blueberries (both species combined) on sprayed clearcuts in 1995 and 1996. Single and multiple treatments also significantly (P <= 0.05) reduced fresh mass and dry mass of total berries in 1995 and 1996. Compared with the controls, reductions in cover for both blueberry species were only significant (P <= 0.05) with the Vision® treatments. In clearcuts where V. angustifolium forms a major component of the Vaccinium spp. cover, the short-term reduction in fruit availability in sprayed areas may be considerable.

The Lowbush blueberry industry in Eastern Canada

A great number of morphologically distinctive blueberry populations, representing many species and suggesting extensive hybridization (16), occur throughout North America. The east Canadian population consists essentially of four species (25, 2, 3). Oddly enough, although these differ in form as described below, the fruits are quite similar in size, flavor and extent of waxy bloom. They have been harvested from the wild for generations and, together, with venison, were a major component of the Indian's pemmican. Vaccinium corymbosum L., the highbusb blueberry, occurs in swamps and lake-marginal regions throughout southwestern NovaScotia. The native population is too limited to be of commercial importance, but cultivars selected in the United States have been propagated and planted in increasing numbers in this area. A diminutive species, Vaccinium boreale Hall & Aalders, occurs in exposed northern regions of Cape Breton Island and in Newfoundland (25). It is not economically important. The two species of lowbush blueberries that constitute the bulk of the native crop occur together in most blueberry fields. The velvet-leaf blueberry, Vaccin.ium myrtilloides Michx., predominates in fields newly developed from woodlots. The common lowbush blueberry, Vaccinium angustifolium Ait., dominates in fields developed from abandoned hay fields (24), and the produce from this constitutes more than three-quarters of all lowbush blueberry production. For many years, attempts have been made to cultivate blueberries. This has resulted,