Evidence of functional gender polymorphisms in a population of the hermaphroditic lowbush blueberry (Vaccinium angustifolium)¹This article is part of a Special Issue entitled “A tribute to Sam Vander Kloet FLS: Pure and applied research from blueberries to heathland ecology”.

Abstract

Lowbush blueberry (Vaccinium angustifolium Aiton) is a wild, but cultivated for profit, agricultural system grown primarily in the northeastern regions of North America. It has been suggested that a functional gender specialization may be occurring in this hermaphroditic species in which some individuals (termed clones) effectively function as bearers (high ovule production but little or nonviable pollen) or as pollen donors (low ovule number with high quantities of viable pollen). The purpose of this study was to investigate if functional gender specialization was occurring in a randomly chosen population of 56 clones from the Blueberry Hill Research Farm in Jonesboro, Maine. For each clone, the mean number of ovules and the mean number of viable microspores per flower were determined. From this, functional gender was calculated. Five out of 56 clones, or approximately 10% of clones, were found to be functioning primarily as females, owing to their low levels of viable pollen. Thus, some evidence was found of a functional gender specialization occurring-the presence of a few plants that were nearly male-sterile. Since the most common evolutionary pathway to gynodioecy involves the invasion of male steriles, it is interesting to speculate that a trend towards gender dimorphism could be occurring in lowbush blueberry.Résumé : Le bleuet nain vivant à l'état sauvage est également cultivé de façon profitable, selon un système agricole pratiqué surtout dans les régions du nord-est de l'Amérique du Nord. On a suggéré qu'une spécialisation fonctionnelle des genres puisse exister chez cette espèce hermaphrodite chez laquelle certains individus (appelé clones) fonctionneraient comme porteurs (forte production d'ovules, mais peu ou pas de pollen viable) ou donneur de pollen (faible nombre d'ovules avec de grandes quantités de pollens viables). Les auteurs se sont proposé d'examiner si la spécialisation fonctionnelle des genres se présente chez une population choisie au hasard, constituée de 56 clones provenant de la Blueberry Research Farm, à Jonesboro dans le Maine. Ils ont déterminé pour chaque clone le nombre moyen d'ovules et de microspores viables par fleur, et ils ont calculé à partir de ces données les genres fonctionnels. On a constaté que cinq des 56 clones, environ 10 %, fonctionnent surtout comme femelles, dû surtout à la faible production de pollen viable. Ainsi, les auteurs ont trouvé une certaine preuve de l'existence d'une spécialisation des genres, soit la présence de quelques plantes à stérilité mâle presque totale. Puisque le cheminement évolutif le plus commun vers la gynodiécie implique la stérilité mâle, il est devient intéressant de spéculer qu'il pourrait exister une tendance vers le dimorphisme des genres chez le bleuet nain.Mots-clés : fertilité, ovules, viabilité du pollen, hermaphrodite, genre fonctionnel, système de croisement.[Traduit par la Rédaction]

Analysis of Pollination Services Provided by Wild and Managed Bees (Apoidea) in Wild Blueberry (Vaccinium angustifolium Aiton) Production in Maine, USA, with a Literature Review

“…In this hermaphroditic species, flowers have an average of 63.4 ± 6.9 (SD) ovules and 2150.7 ± 965.0 pollen tetrads [72]. There is no correlation between the number of ovules and the number of pollen tetrads in a flower and, on the basis of frequency distributions of ovule and pollen counts, it appears that a shift toward female gender and, thus, gender dimorphism is occurring in wild blueberry [68,72]. Clones exhibit self-incompatibility and require outcrossing [31,[73][74][75], although Bell et al [75] found that 20% of clones have high levels of self-compatibility and that outcrossing was non-reciprocal.…”

“…Individual flower viability is 8-10 days with maximum stigma receptivity at 1-3 or 4 days, depending upon the year [70]. In this hermaphroditic species, flowers have an average of 63.4 ± 6.9 (SD) ovules and 2150.7 ± 965.0 pollen tetrads [72]. There is no correlation between the number of ovules and the number of pollen tetrads in a flower and, on the basis of frequency distributions of ovule and pollen counts, it appears that a shift toward female gender and, thus, gender dimorphism is occurring in wild blueberry [68,72].…”

Genetic Diversity of Lowbush Blueberry throughout the United States in Managed and Non-Managed Populations

“…Forests are harvested and the existing understory blueberry plants become established.The underlying genetic diversity of lowbush blueberry is relatively unknown compared to other fruit crops [8]. Recently, a variety of techniques and molecular markers have been used to investigate the genetic heterogeneity and relatedness of V. angustifolium populations [1,8,[10][11][12][13][14][15]. These studies have shown V. angustifolium to be highly diverse in Maine and the Canadian Maritimes.…”

The Ecology of Autogamy in Wild Blueberry (Vaccinium angustifolium Aiton): Does the Early Clone Get the Bee?

“…There is still much that is not known about wild blueberry reproduction. Several investigations into the plant role in wild blueberry pollination and plant reproduction have advanced our knowledge into the areas of tradeoffs in reproductive effort investment [21,22], reproductive self-incompatibility/compatibility [17,18,[23][24][25], spatial genetic structure and relatedness [26][27][28], reproductive tissue investment [29], gene flow measured as pollen movement from donor to recipient clone [30,31], timing of flower bud production [9,32] and flowering [9,32], plant plasticity in regards to physiological responses in growth and development and the effects of climate warming on blueberry pollination [33,34]. One topic that has not been researched is the ecology of autogamy in the reproduction of wild blueberry, the focus of this study.…”