Author
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 6/26/2014 Publication Date: 7/21/2014 Citation: Yocum, G.D., Rinehart, J.P. 2014. Use of fluctuating thermal regimes and decreased oxygen during storage improves survival of post-diapause Megachile rotundata (abstract). Dormancy Management to Enable Mass-rearing and Increase Efficacy of Sterile Insects and Natural Enemies. Report of the First Research Coordination Meeting of an FAO/IAEA Coordinated Research Project. 07/21/2014 to 07/25/2014. Vienna, Austria. p. 37. Interpretive Summary: The alfalfa leafcutting bee, Megachile rotundata, is the world’s most intensively managed solitary bee. M. rotundata is used primarily for alfalfa seed production in the northwestern United States and western Canada, but also provides pollination services for carrot, hybrid canola, onion, various legumes and other specialty crops. Under normal management practices, M. rotundata are overwintered as diapausing prepupae using a constant temperature (4-6°C) regime from late September until early spring of the following year. Those prepupae not used or sold are an economic loss to the producers. An improved storage protocol for diapausing and post-diapausing quiescent prepupae would decrease economic loss to the producers and help stabilize year-to-year cost fluctuation for customers. Our working hypothesis is: Any protocol that delays the onset of mortality also delays the onset of sublethal effects that degrade pollinator quality. Our first objective was to determine if diapausing prepupae could be stored for more than one year. We have clearly demonstrated that insect tolerance to low-temperature exposure can be significantly increased by a fluctuating thermal regime (FTR): short high temperature pulses during the low-temperature exposure. Storing diapausing and post-diapausing prepupae under FTR extended their survival into the second post-wintering growing season. We achieved further gains in storage duration by decreasing the concentration of oxygen the prepupae were exposed to during storage. Post-diapausing prepupae stored under FTR and under 10% oxygen survived 23 months without significant decrease in survival. To further our understanding of storage physiology of M. rotundata, we conducted two RNA-seq experiments. In the first, post-diapausing prepupae were stored under either constant 6°C or under FTR. Within the FTR treatment, transcripts involved in ion homeostasis, various metabolic pathways, and oxidative stress response were upregulated. In the second experiment, two groups of prepupae were collected depending on when they entered diapause (early and late season). The two groups were further subdivided according to how they were overwintered (constant 6°C or under field conditions). Samples were collected from the four treatments from October to June. Approximately 6400 differentially regulated transcripts were isolated. One notable observation was that there were environmental- (laboratory versus field) and seasonal- (early versus late) specific differentially regulated transcripts. These results indicate that diapause offers unique opportunities for significant improvement in storage of M. rotundata as well as for other agriculturally important insects. Technical Abstract: The alfalfa leafcutting bee, Megachile rotundata, is the world’s most intensively managed solitary bee. M. rotundata is used primarily for alfalfa seed production in the northwestern United States and western Canada, but also provides pollination services for carrot, hybrid canola, onion, various legumes and other specialty crops. Under normal management practices, M. rotundata are overwintered as diapausing prepupae using a constant temperature (4-6°C) regime from late September until early spring of the following year. Those prepupae not used or sold are an economic loss to the producers. An improved storage protocol for diapausing and post-diapausing quiescent prepupae would decrease economic loss to the producers and help stabilize year-to-year cost fluctuation for customers. Our working hypothesis is: Any protocol that delays the onset of mortality also delays the onset of sublethal effects that degrade pollinator quality. Our first objective was to determine if diapausing prepupae could be stored for more than one year. We have clearly demonstrated that insect tolerance to low-temperature exposure can be significantly increased by a fluctuating thermal regime (FTR): short high temperature pulses during the low-temperature exposure. Storing diapausing and post-diapausing prepupae under FTR extended their survival into the second post-wintering growing season. We achieved further gains in storage duration by decreasing the concentration of oxygen the prepupae were exposed to during storage. Post-diapausing prepupae stored under FTR and under 10% oxygen survived 23 months without significant decrease in survival. To further our understanding of storage physiology of M. rotundata, we conducted two RNA-seq experiments. In the first, post-diapausing prepupae were stored under either constant 6°C or under FTR. Within the FTR treatment, transcripts involved in ion homeostasis, various metabolic pathways, and oxidative stress response were upregulated. In the second experiment, two groups of prepupae were collected depending on when they entered diapause (early and late season). The two groups were further subdivided according to how they were overwintered (constant 6°C or under field conditions). Samples were collected from the four treatments from October to June. Approximately 6400 differentially regulated transcripts were isolated. One notable observation was that there were environmental- (laboratory versus field) and seasonal- (early versus late) specific differentially regulated transcripts. These results indicate that diapause offers unique opportunities for significant improvement in storage of M. rotundata as well as for other agriculturally important insects. |
