Pollen biology and reproductive ecology of selected paleotropical Dendrobiums (orchids) and their commercial hybrids

By Weerasinghe Elena Rumalie Silva, Harshini Herath, Sena Ratnayake, Renuka Nilmini Attanayake, and Priyanganie Senanayake

  

Reproductive traits such as fruit set, pollen traits are crucial for the development of novel hybrids in ornamental plants including dendrobiums. Orchids contain ‘pollinia’ as their pollen dispersal units, where a large number of pollen grains are packed together. Pollination of orchids occurs by the deposition of pollinia in the receptive stigmatic cup. Pollen viability and pollen germinability are considered as indicators of a successful hybridisation process.

Indigenous Dendrobium species (A) D. crumenatum and (B) D. anosmum and commercial Dendrobium hybrids (C) Dendrobium ‘Big Jumbo’, (D) Dendrobium ‘Emma White’, (E) Dendrobium ‘Pink’, (F) Dendrobium ‘Lemon Yellow’ , (G) Dendrobium ‘Arading Green’, (H) Dendrobium ‘Nana Red’, (I) Dendrobium ‘Mickey Pinky Splash’, (J) Dendrobium ‘Visa Peach’, (K) Dendrobium ‘Sonia red’ and (L) Dendrobium ‘Happy Star’.

In the present research, pollen viability, germinability and success in seed production of two indigenous Dendrobium species and ten commercial hybrids of Dendrobium were compared to determine the fitness traits and the possibility of the compromising of fitness in commercial hybrids. Reproductive ecology of indigenous and commercial hybrids were studied by observing visits of natural pollinators. Floral characters that are associated with different groups of pollinators were assessed to determine the type of pollinators that are associated with the studied dendrobiums. Effect of pollen storage temperature on seasonally flowering D. crumenatum pollen viability was assessed to determine the suitable pollen storage method for the benefit of breeding programmes.

Indigenous species, D. crumenatum and D. anosmum, showed the highest pollen viability and germinability while only 40% of the commercial hybrids had viable pollen and could be identified as desired hybrids for successful breeding programs. D. crumenatum pollen can be stored at 9°C maintaining its viability for 14 days for successful cross-pollination. Although all tested dendrobiums predicted to be pollinated by bees, they failed to set fruit under natural pollination due to the lack of native pollinators in the suburban environment. Thus, fruit set in tested dendrobiums were reported only through hand pollination. In addition, indigenous D. crumenatum can be recommended to use as pollen donors in cross-pollination programmes. Our findings facilitate the selection of parents with desired traits of promising features to create novel hybrids for commercial purpose.

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Genotype and environment effects on sunflower nectar and their relationships to crop pollination

by Jarrad R. Prasifka, Beth Ferguson, and Karen K. Fugate

 

Sunflower

The nectar reward a sunflower provides to bees depends on the type or ‘variety’ and the conditions, especially temperature, in which the crop grows. To better understand how pollinators choose which sunflowers to visit, several sunflower varieties were grown under different temperatures and nectar collected from the flowers. Separate experiments also looked at how mesh bags (used to keep bees from moving pollen in breeding or insect research) change the nectar rewards available to bees. In general, much more nectar was found when plants were grown in warmer temperatures, but not all varieties showed the same pattern. The different temperatures in which plants were grown caused only small changes in nectar concentration or the types of sugars found in nectar. Sunflower plants covered with mesh bags contained much more nectar, and far more bees visited these plants when bags were removed. Even though not all varieties react to temperature changes in the same way, plant breeders can still create sunflowers that provide more nectar to bees. Because of how mesh bags change nectar rewards, research on sunflower pollination should avoid using these bags when possible.

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Parasites, parasitoids, and hive products that are potentially deleterious to wild and commercially raised bumble bees

 By Evans et al.

A queen Bombus appositus extends her proboscis as
she approaches an inflorescence of Corydalis caseana
brandegeei in the Colorado Rocky Mountains.
Photo by David W. Inouye.

Bumble bees (genus Bombus) are important pollinators of many wild and cultivated plants. Across the globe, many bumble bee species have been found to be in decline, with declines often linked to parasites. Here, we provide information about risks to wild and domesticated bumble bee colonies from external parasites (mites), internal parasites (parasitic nematodes, flies and wasps), and other insects that sometimes live in bumble bee nests (beetles and moths). We discuss methods for their detection, quantification, and control. In addition, we assess honey bee hive products such as pollen and wax that are used in commercial bumble bee production, and may pose risks to bumble bees as routes that can introduce parasites and pathogens into commercial rearing facilities. These potential threats need to be managed in the context of national and international commercial trade in bumble bees to prevent pest introduction and pathogen spillover that can threaten wild native bees.  

 

Read the scientific publication in JPE.