Hand Pollination Research Articles

Limited pollen flow and high selfing rates toward geographic range limit in an Atlantic forest bromeliad

Bromeliaceae is a Neotropical family that evolved ecological key innovations in association with extensive adaptive radiation. Its species present a variety of different mating system strategies varying within and among species, within genera and subfamilies. Also, species with a wide geographical range can display large variation in mating system, reproductive success and genetic diversity. Here we combined data from hand pollinations and genetic analysis to assess outcomes of contemporary gene flow and mating system variation at the range edge of Vriesea gigantea. Results from pollen germination rates showed that this species is cryptically self-incompatible. Hand-pollination experiments and genetic analysis of progeny arrays revealed that V. gigantea has a mixed mating system, with high selfing rates (s=0.612), and high inbreeding coefficient (F=0.372). Inbreeding in V. gigantea at southern edge of its distribution range was caused by high levels of selfing rather than by mating among relatives. Moreover, strong pollen pool genetic structure was observed (Φ’FT=0.671), with an increase from north to south. The parameters observed help us to understand historical and ecological conditions under which V. gigantea has experienced moderate to high levels of selfing in the face of reduced pollen flow from central to peripheral populations due to recent southward range expansion.

Biotic and abiotic factors contribute to cranberry pollination

As bee populations continue to decline, farmers face possible crop failures due to insufficient pollination. Crops, however, vary in the degree to which they depend on pollinators, suggesting that some crops may not be as sensitive to variation in pollinator availability and/or abundance as others. The objective of this study was to determine the contribution of biotic and abiotic factors to cranberry pollination. We performed field and greenhouse experiments to compare the effect of biotic (i.e., bee or hand pollination) and abiotic (i.e., wind, agitation) factors on yield. We found that even in the absence of bees, cranberry is able to produce a significant yield. In the field, plants in the abiotic treatments produced higher yields (wind 230 bbl/ac [barrels per acre], agitation 200 bbl/ac) than the closed control treatment (108 bbl/ac), although these yields were not as high as the open, biotic treatment (367 bbl/ac). This corresponds to a contribution of 41% by bees, 30% by non-bee insects, and 29% by mechanical agitation. In the greenhouse, the agitation treatment had, on average, higher berry weight per upright (0.6 g/upright) than the undisturbed control treatment (0.04 g/upright), but again, not as high as the biotic treatment (3.0 g/upright). This confirmed that cranberry does not autogamously self-pollinate indicating that all yields are due to biotic or abiotic vectors moving pollen between flowers. Although bees clearly contribute to cranberry pollination, previous studies have understated the contribution of alternative mechanisms by which cranberry pollen can move between flowers.

Effect of pollination method and pollen source on fruit set and growth of red-peel pitaya (Hylocereus spp.) in Taiwan

SummaryWe explored the effects of pollination method (hand cross-, hand self-, automatic self-, and open-pollination) and pollen source on fruit set and growth in four red-skinned pitaya (Hylocereus spp.) cultivars [‘Vietnam White’ (‘VNWhite’), ‘Chaozhou 5’, ‘Orejona’, and ‘F11’] in Taiwan.‘VN-White’ has white flesh, while the other three cultivars have red flesh. There were no significant differences in pollen viability or germination rate among the four cultivars, irrespective of whether the pollen was collected at night (approx. 20.30 h) or on the following morning (approx. 08.30 h).The results also indicated that ‘VN White’ was fully self-compatible and exhibited a high fruit set percentage (80 - 96%) following all pollination treatments. This cultivar produced the largest fruit from both hand self- and openpollination, compared to the three other cultivars tested. ‘Chaozhou 5’ was partly self-compatible, and ‘Orejona’ and ‘F11’ were completely self-incompatible. Hand cross-pollination significantly increased the fruit set percentages and mean fruit fresh weights (FWs) in ‘Chaozhou 5’ and ‘Orejona’. Pollen source also significantly affected the fruit set percentage and fruit FW. ‘VN-White’ (after self-pollination) and ‘Chaozou 5’ (after crossing with ‘VN-White’) gave superior fruit set percentages and fruit FWs. Reciprocal crosses between ‘Orejona’ and ‘F11’ also resulted in high fruit set percentages as well as large fruit in both cultivars. Therefore, the source of pollen and the method of pollination can affect fruit production in some cultivars of pitaya. Self-compatibility in ‘VN-White’ concurs with the morphology of its flowers in which the anthers lie in close proximity to the stigma.The distance between the anthers and the stigma may be used an indicator of whether hand pollination is necessary for a pitaya cultivar.

An invasive plant alters pollinator-mediated phenotypic selection on a native congener.

• Recent studies suggest that invasive plants compete reproductively with native plants by reducing the quantity or quality of pollinator visits. Although these studies have revealed ecological consequences of pollinator-mediated competition between invasive and native plants, the evolutionary outcomes of these interactions remain largely unexplored.• We studied the ecological and evolutionary impact of pollinator-mediated competition with an invasive jewelweed, Impatiens glandulifera, on a co-occurring native congener, I. capensis. Using a pollinator choice experiment, a hand pollination experiment, and a selection analysis, we addressed the following questions: (1) Do native pollinators show preference for the invasive or native jewelweed, and do they move between the two species? (2) Does invasive jewelweed pollen inhibit seed production in the native plant? (3) Does the invasive jewelweed alter phenotypic selection on the native plant's floral traits?• The pollinator choice experiment showed that pollinators strongly preferred the invasive jewelweed. The hand pollination experiment demonstrated that invasive pollen inhibited seed production in the native plant. The selection analysis showed that the presence of the invasive jewelweed altered phenotypic selection on corolla height in the native plant.• Invasive plants have the potential to alter phenotypic selection on floral traits in native plant populations. If native plants can evolve in response to this altered selection pressure, the evolution of floral traits may play an important role in permitting long-term coexistence of native and invasive plants.

Pollination Services of Mango Flower Pollinators.

Measuring wild pollinator services in agricultural production is very important in the context of sustainable management. In this study, we estimated the contribution of native pollinators to mango fruit set production of two mango cultivars Mangifera indica (L). cv. ‘Sala’ and ‘Chok Anan’. Visitation rates of pollinators on mango flowers and number of pollen grains adhering to their bodies determined pollinator efficiency for reproductive success of the crop. Chok Anan failed to produce any fruit set in the absence of pollinators. In natural condition, we found that Sala produced 4.8% fruit set per hermaphrodite flower while Chok Anan produced 3.1% per flower. Hand pollination tremendously increased fruit set of naturally pollinated flower for Sala (>100%), but only 33% for Chok Anan. Pollinator contribution to mango fruit set was estimated at 53% of total fruit set production. Our results highlighted the importance of insect pollinations in mango production. Large size flies Eristalinus spp. and Chrysomya spp. were found to be effective pollen carriers and visited more mango flowers compared with other flower visitors.

Preliminary studies on ornithophilous floral visitors in the Australian endemic <i>Passiflora herbertiana</i> Ker Gawl. (Passifloraceae)

The pollination biology of the Australian endemic species Passiflora herbertiana (Passiflora subgenus Decaloba, supersection Disemma, section Disemma) was investigated in a single population growing in the Witches Falls section of Mount Tamborine National Park, Queensland. Three native honeyeaters were observed at the flowers, including Lewin’s Honeyeater (Meliphaga lewinii), the Noisy Miner (Manorina melanocephala), and the Eastern Spinebill (Acanthorhynchus tenuirostris). Visitation began at 07:30 and ended by 15:30 each day. The most frequent visitor was Lewin’s Honeyeater. Flowers typically began anthesis in the afternoon, with a small number of flowers opening in the early morning. Flowers remained open between four and five days, even after successful pollination. Both the age of the flower and the amount of sun exposure were determined to affect perianth colour change from pale yellow to salmon-pink. Andromonoecy was observed infrequently in the population; most plants exhibited bisexual flowers, but a small number of individuals exhibited both hermaphroditic and male flowers with short styles held permanently erect. Controlled hand pollinations indicated that P. herbertiana is self-compatible but is not autogamous. Pollen tubes required at least 48 hours to reach the most apical ovules within the ovary. These data provide new insights into the evolution of ornithophily in the Old World Passiflora. Link to Appendix 1: Video showing Lewin’s Honeyeaters visiting various P. herbertiana flowers

Reproductive biology of Ziziphus mistol Griseb. (Rhamnaceae), a wild fruit tree of saline environments

Ziziphus comprises important fruit trees that inhabit arid environments of tropical and subtropical regions of the world and are able to adapt to drought and salt stress. Species of this genus are characterized by synchronous protandrous dichogamy and self-incompatibility; however, reduced seed set after hand self-pollination indicates that self-fertilization is possible and that it causes a strong inbreeding depression. We characterize the reproductive biology of Ziziphus mistol, a species typical of saline environments of Chaco American forests. For this purpose, we studied floral biology, observed foraging behavior and pollen load of captured floral visitors, and tested the breeding system through the assessment of fruit and seed set and pollen tube growth following self-, cross-, and open pollinations treatments. In addition, the dependence of a pollinator and autonomous self-pollination were evaluated by excluding floral visitors and airborne pollen. Cross-compatibility between individuals was tested through controlled hand pollinations. Results indicate that Z. mistol is predominantly outcrossing and depends on its pollinators to produce fruits and seeds. We observed high synchrony of flowering between individuals, as well as in floral anthesis between/within inflorescences within individuals. The flowers exhibit complete intrafloral dichogamy that fully prevents autonomous self-pollination, while sexual phases overlap within inflorescence; thus geitonogamy can easily occur. Manipulative experiments show that Z. mistol can set fruits and seeds after self- as well as cross-pollinations. However, reduction in fruit set and seed set after selfing and/or cessation of pollen tube growth in the style suggest a self-incompatible system. From reciprocal crosses tested (N=95), we have identified only 32.6% compatible crosses via fruit and seed trials. We suggest that in Z. mistol, as well as in other species of the genus, both synchrony in floral development and partial self-incompatibility would be evolved to reduce the costs of inbreeding.

Effect of different modes of pollination on quantitative and qualitative parameters of Egyptian Clover, Trifolium alexandrinum L.

The effect of different modes of pollination on quantitative and qualitative parameters of Egyptian clover, Trifolium alexandrinum L. was studied at Forage Section, Department of Genetics and Plant Breeding, CCS, Haryana Agricultural University, Hisar during 2012 and 2013. Maximum seed setting (81.5%) was recorded in A. mellifera pollination with an 8 frame colony (BP-8F) followed by 4 frame colony (BP-4F) (75.1%), open pollination (OP) (73.8%) and 2 frame colony (BP-2F) (71.5%). Maximum seed yield (2662.3 seeds) was observed in treatment BP-8F followed by BP-4F (2373.8), OP (2316.3) and BP-2F (2235.5). Still lower yield of 2103.0 seeds was found in hand pollination (HP) treatment that was significantly higher than the without insect pollination (WIP) treatment (1114.2). Minimum 1000-seed weight was observed in WIP (2.64 g). The seed weight of BP-4F (3.30), HP (3.20), BP-2F (3.17) and OP (3.03), the heaviest seeds were recorded in BP-8F (3.62 g/1000 grains) and it was at par with the treatment BP-4F (3.30 g). Highest seed germination per cent was recorded in BP-8F (94.7) followed by OP (90.7%). Lowest germination was found in WIP (84.7%). Though some work has been done on this aspect in India but comprehensive pollination studies has not been worked out.

Hand Pollination of Tomato for Breeding and Seed Production

Hand pollination is a technique that is used for breeding new tomato varieties with desirable characteristics such as plant vigor, disease resistance, and uniform fruit quality and plant growth; since tomatoes have complete flowers and are self-pollinated, it usually is unnecessary to hand pollinate the flowers for fruit production. This 4-page guide illustrates selection and emasculation of flowers from the plant receiving pollen, pollen collection and drying, and pollination of the stigma. Written by Monica Ozores-Hampton, and published by the UF Department of Horticultural Sciences, August 2014. (Photo credit: Monica Ozores-Hampton)

Effects of exogenous application of GA4+7 and N-(2-chloro-4-pyridyl)-N′-phenylurea on induced parthenocarpy and fruit quality in Pyrus pyrifolia ‘Cuiguan’

Parthenocarpy largely depends on the coordinated action of hormones produced in unpollinated ovaries, but can be induced by application of exogenous hormones. We evaluated the effects of gibberellins (GA4+7) and 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) on induction and quality of parthenocarpic fruit in Pyrus pyrifolia Nakai ‘Cuiguan’ pear. Parthenocarpic fruit with a small core and a high edible ratio were induced by GA4+7 and/or CPPU. GA4+7 application induced normally shaped fruit with superior quality and normal size, whereas CPPU treatments resulted in abnormally shaped fruit with a larger size and an extraordinarily expanded calyx tube. Among all GA4+7 treatments, 500 mg L−1 GA4+7 induced the highest fruit set (91.88 %) and increased fruit size by 85 % compared with fruit induced by 200 mg L−1 GA4+7. In addition, the parthenocarpic fruit induced by GA4+7 accumulated considerably higher quantities of sucrose and less organic acids than pollinated and CPPU-induced fruit. The potential commercial application of CPPU and GA to pear in place of hand pollination is discussed.

Optimization of controlled pollination in avocado (Persea americana Mill., Lauraceae)

Avocado has a singular synchronous protogynous dichogamy breeding system that promotes outcrossing. In this work different steps have been optimized to improve controlled pollinations in avocado in order to perform basic studies of reproductive biology and directed crosses in breeding programs. The results show that, in order to achieve successful fruit set, male flowers should be collected when all the anthers have dehisced and the pollen transferred by direct contact of the anthers with the stigma during the female stage using preferentially determinate inflorescences and pollinating at least 11 flowers per inflorescence. To perform crosses between cultivars of complementary floral groups, the flowers should be stored under high relative humidity during the hand pollination process. When the crosses involved cultivars of the same floral group, the male flowers should be collected just before anther dehiscence and could be stored for several days at 4°C. Pollen application should be performed preferentially on flowers within determinate inflorescences or within indeterminate inflorescences where vegetative growth has been removed. The results obtained are useful to optimize controlled pollinations in avocado and can help to increase fruit set in breeding programs and avoid the incorrect interpretation from pollination experiments in studies of reproductive biology.

A study on floral phenology, pollination mechanisms and molecular characterisation of pollinator in Bulbophyllum careyanum (Orchidaceae)

The present study focuses on flowering phenology, pollinator intensity in Bulbophyllum careyanum during different times of the day and visitation rates with the number of flowers per inflorescence. The average time taken from bud initiation of inflorescence till its maturity (27.4±0.79 days), flower longevity (15.3±1.09 days) and wilting period (4.2±0.27 days) were almost same during flowering seasons in two consecutive years (2012 and 2013). However, inflorescence bud initiation and flower opening delayed for about three weeks during 2013 as compared to the former. Hand pollination and bagging experiments showed that induced and spontaneous autogamy, agamospermy and geitonogamy failed to produce fruits, but flowers under natural conditions (control) and those introduced to xenogamy produced fruits with 23.3% and 86.7% respectively. Pollinators mostly visited the flowers during morning hours (0615-0645) and evening hours (1645-1710). Pollinator visitation rates were significantly correlated with the number of flowers per inflorescence (r values ranges from 0.84 to 1.00, significant at 0.01). Molecular characterisation of the pollinators were done by Polymerase Chain Reaction (PCR) amplification of four mitochondrial gene fragments (12s rDNA, 16s rDNA, Cytochrome c oxydase I and NADH 4 & 5 dehydrogenase). Different insect species including flies, wasps, grasshoppers and bees visited the B.careyanum flowers, but only Drosophila melanogaster was found to be the real pollinator.

Pollination services provided by wild insects to kiwifruit (Actinidia deliciosa)

Managed bees are used to transfer pollen from male to female flowers in kiwifruit, but the contribution of wild insects has been long overlooked. We approached such contribution with multiple criteria (pollinator abundance, foraging behavior, pollinating efficiency, and response to weather conditions) in the absence of imported colonies. An abundant and rich community of pollinators (57 % were non-Apis insects) visited kiwifruit flowers and assured a fruit set and size not different from those obtained by optimal hand pollination. Honeybees were more abundant and visited more flowers per time but bumblebees were more efficient on a per-visit basis. Other taxa are expected to contribute less because of their lower numbers (hoverflies, wild bees, butterflies, beetles) or their passive behavior (non-syrphid flies). Visitation patterns of pollinators were complementary. Our results highlight the important contribution of wild insects to the pollination of kiwifruit.

Does sexual reproduction matter for a rare clonal species in frequently disturbed habitats?1

Sexual reproduction is often considered essential for evolutionary change, with many plants possessing mechanisms to promote outcrossing and produce genetically variable offspring. Many plant species, however, are also capable of asexual reproduction, but its relative role in population dynamics is often overlooked. Given that sexual reproduction depends in part on mate availability and therefore plant density, would asexual reproduction predominate in rare species, especially those found in highly disturbed habitats? To explore this question, we used field and genetic techniques to investigate the reproductive system of a rare, clonal shrub, Spiraea virginiana Britton, which inhabits the frequently disturbed riparian zone. We performed controlled hand pollinations within and among individuals both within and across populations. We also quantified allelic richness and heterozygosity at a locus purported to control self-incompatibility (SI). Hand pollinations resulted in low total fruit production but more infructescences were produced with outcross pollen (20%) than with self-pollen (2.3%). Low allelic richness (2–7 alleles/population) was found at the putative SI-locus; variation at this locus did not correspond directly with the pollination results, suggesting either the SI system is leaky or that the examined SI-locus is not primarily responsible for incompatibility in this species. This study shows that rarity combined with clonality within a highly disturbed habitat may promote a combination of asexual and sexual reproduction. Although sexual reproduction can occur, it may be limited by a scarcity of available mates for S. virginiana, thereby resulting in primarily asexual reproduction in the species.

Insect pollination and self-incompatibility in edible and/or medicinal crops in southwestern China, a global hotspot of biodiversity.

An increasing global demand for food, coupled with the widespread decline of pollinator diversity, remains an international concern in agriculture and genetic conservation. In particular, there are large gaps in the study of the pollination of economically important and traditionally grown species in China. Many plant species grown in China are both edible and used medicinally. The country retains extensive written records of agricultural and apicultural practices, facilitating contemporary studies of some important taxa. Here, we focus on Yunnan in southwestern China, a mega-biodiversity hotspot for medicinal/food plants. We used plant and insect taxa as model systems to understand the patterns and consequences of pollinator deficit to crops. We identified several gaps and limitations in research on the pollination ecology and breeding systems of domesticated taxa and their wild relatives in Yunnan and asked the following questions: (1) What is known about pollination systems of edible and medicinal plants in Yunnan? (2) What are the most important pollinators of Codonopsis subglobosa (Campanulaceae)? (3) How important are native pollinator species for maximizing yield in Chinese crops compared with the introduced Apis mellifera? We found that some crops that require cross-pollination now depend exclusively on hand pollination. Three domesticated crops are dependent primarily on the native but semidomesticated Apis cerana and the introduced A. mellifera. Other species of wild pollinators often play important roles for certain specialty crops (e.g., Vespa velutina pollinates Codonopsis subglobosa). We propose a more systematic and comprehensive approach to applied research in the future.

Standardization of cost effective hybridization technique for hybrid seed production in okra (Abelmoschus esculentus)

Due to lack of stable male sterile system in okra [Abelmoschus esculentus (L.) Moench], hybrid seed production is still dependant on hand emasculation and pollination which is troublesome and labour intensive. Five hybridization techniques, viz. Hand emasculation and pollination (conventional method); One day premature bud cutting and pollination next day morning; Two days premature bud cutting and pollination next day morning; Mature bud cutting and pollination immediately thereafter and One day premature bud cutting and pollination next morning just after spray of 10% sugar solution were used in the study to standardize the cost effective hybridization technique based on two marker lines, viz. 678-2 (red pigmented with five ridges) and IIVR-10 (green fruited with seven ridges) as male parent and VRO-6 (green fruited with five ridges) as female parent. Percentage of fruit set was maximum in pigment based marker (60.82%) as compared to ridge based marker (57.40%), in general, and hand emasculation and pollination method in colour based marker, in particular, whereas number of seeds/fruit was recorded maximum (44.85) in one day premature bud cutting and pollination next morning. Time requirement for 100 flower bud hybridization (emasculation and pollination) was found maximum in hand emasculation and pollination method (198 minutes) and minimum in the treatment two days premature bud cutting and pollination next morning (69.5 minutes). Maximum time saving was observed in the treatment two days premature bud cutting and pollination next morning (64.88%) over hand ema sculation and pollination method, whereas minimum time saving over hand emasculation and pollination was observed in the treatment one day premature bud cutting and pollination next morning just after 10% sugar solution spray (44.72 %). As far as the economics of the 100 hybridized fruit set is concerned, the two days premature bud cutting and pollination next morning (Rupees 20.60) followed by one day premature bud cutting and pollination next morning (Rupees 21.82), which were significantly at par, were the most economical methods.

Effects of storage length and flowering stage of pollen influence its viability, fruit set and fruit quality in ‘Red’ and ‘Lessard Thai’ sugar apple (Annona squamosa) and ‘Gefner’ atemoya (A. cherimola × A. squamosa)

The fruit set of commercial Annonaceae pollinated by natural pollinators is generally insufficient to produce commercially acceptable yields. In addition, several studies have reported that both the pollen source and age affect the potential percent fruit set of sugar apple and atemoya. Annona flowers are hermaphrodite; however, the female part mature before the male, which is known as dichogamy of the protogynous type. The objectives of the present study were to determine the effect of pollen storage duration on pollen viability; the percent fruit set by hand pollination of ‘Red’ sugar apple, ‘Lessard Thai’ green sugar apple and ‘Gefner’ atemoya; and resulting fruit characteristics as a result of pollen source in South Florida. Hand pollination and in vitro pollen germination tests were arranged in a 3×5 factorial design, with three cultivars, five treatments, and five replicates per treatment. The percentage of in vitro pollen germination was the highest for ‘Red’ sugar apple pollen (26.5%) collected from male stage flowers and for pollen collected from female stage flowers collected late afternoon and germinated 18h later (23%). Percent pollen germination was higher for ‘Lessard Thai’ (∼33%) than for ‘Red’ sugar apple and pollen storage for up to 24h was not significantly different than male stage pollen used immediately and pollen collected from female stage flowers and used 18h later. ‘Gefner’ atemoya pollen did not germinate when pollen grains were collected from male stage flowers and when using female stage flowers collected late afternoon and stored for 72h. Fruit set and fruit quality varied significantly as a result of pollen storage treatments. Hand pollination promoted high percentages of fruit set, greater than 80% when female stage flowers were collected late afternoon and hand pollination performed 18h after collection. Fruit harvested as a result of the various pollen storage treatments varied significantly in weight, diameter, and the number of seeds per fruit. The pollen from ‘Lessard Thai’ sugar apple and ‘Gefner’ atemoya may be stored up to 24 and 48h, respectively.

Are pollinators the agents of selection for the extreme large size and dark color in Oncocyclus irises?

Pollinator-mediated selection is a major evolutionary driver of floral traits; yet, such selection has rarely been tested for floral extreme traits. The Oncocyclus irises have exceptionally large, dark-colored flowers, associated with night-sheltering pollination and heat reward by the dark flowers. We quantified phenotypic selection on stem length, floral size and color in two species of iris (Iris atropurpurea and I. haynei), using an experimental approach. We estimated selection gradients for both flowers open to natural pollination and for flowers receiving supplementary hand pollination, assuming that open-pollinated flowers are affected by all factors that could influence fitness, whereas supplementary pollination removes the possible influence of pollinators. We found evidence for pollinator-mediated selection to increase floral size and stem length in I. atropurpurea, but floral color in this species was not under pollinator-mediated selection. In I. haynei, no pollinator-mediated selection on any of the traits was detected. We conclude that the extreme floral size of I. atropurpurea has probably evolved as a result of pollinator behavior. Lack of such evidence for I. haynei and for the dark floral color in both species suggests that other non-pollinator agents are selecting for these prominent traits, or that phenotypic color variation in these irises is neutral.

Wild bumble bees reduce pollination deficits in a crop mostly visited by managed honey bees

We assessed the pollinator community of two cultivars of highbush blueberry (Vaccinium corymbosum, Duke and Bluecrop), and determined the importance of different pollinators to overall crop yield by measuring pollination deficits. The importance of distance to putative wild pollinator habitat (natural field edges) for pollinator abundance within fields and crop yield was also considered. Managed honey bees made 70% of flower visits (85% to Duke, 49% to Bluecrop). Wild bumble bees made half of the visits to Bluecrop. Though bumble bees were observed less frequently as distance from the natural edge increased, there was no effect of distance on levels of crop pollination. Pollination deficits were less pronounced in Duke than Bluecrop, with maximum (hand) pollination leading to a 12% (Duke) to 23% (Bluecrop) increase in yield. Exclusion of pollinators reduced yield by 50–80% compared to ambient pollination. For both cultivars, pollination deficits declined most strongly with either increasing bumble bee visits or increasing total visits (honey bees and bumble bees combined), and in no case were deficit levels significantly reduced by honey bees alone. This study supports a growing body of literature that suggests managed honey bees alone cannot reduce deficits, and that wild pollinators are needed to maximize yields in pollinator-dependent agricultural systems.

Inheritance and reproductive consequences of floral anthocyanin deficiency in Silene dioica (Caryophyllaceae).

• Flower color is one of the most important traits for pollinator attraction. However, natural plant populations often harbor rare flower color variants resulting from mutations in biochemical pathways for floral pigment production. It is unclear how such mutations can persist because they can affect not only pollinator visitation but also plant fertility and performance.• We collected rare white-flowered (anthocyanin-deficient) and common pink-flowered morphs of Silene dioica from natural populations in Switzerland. First- and second-generation hybrids between pink and white morphs, as well as backcrosses toward white morphs were produced, and the proportion of white-flowered offspring was determined. We compared seed siring ability and seed production between morphs using hand pollination experiments. Moreover, we scored the transfer of pollen analogues (fluorescent dyes) in a 50:50 array of the two morphs.• The proportions of white-flowered plants in the offspring of our crosses were consistent with more than one recessive mutation as the cause of floral anthocyanin deficiency and further suggested a role of maternal effects for flower color. Seed siring ability and seed set did not differ significantly between pink and white morphs. Pollen transfer occurred preferentially within morphs.• Overall, our results imply that the white morph of S. dioica likely is caused by recessive mutations that do not impair reproduction. However, as this flower color polymorphism led to assortative mating in our experiment, it may represent standing genetic variation with the potential to contribute to evolutionary divergence.