Hot time in the greenhouse
Posted: July 7, 2013
While some of the other lab members have been spending lots of time in the field, Tori and I (plus others, especially Emily) have been spending time in the greenhouse. This is the first summer solely working in the greenhouse, which has both provided opportunities and posed challenges. Working in the greenhouse has allowed me to control variables out of my control in the field and, importantly, has allowed me to (somewhat) easily work at a small spatial scale, increasing the amount of replication I can incorporate into my experiments. This is important because my research is examining the potential of crop genotypic (intraspecific) to improve the resistance and/or resilience of crop fields in the face of stress. Any diversity experiment is a series of tradeoffs. One must make decisions about the number of varieties to include in the experiment, the number of levels of diversity (monoculture vs. three-variety mixtures or monoculture vs. three-variety mixtures AND five variety mixtures), and, ultimately, the number of replicates. Many of these choices limit the other aspects of the experiment because there is only so much space and time. Greenhouse work also poses problems such as broken swamp coolers, extreme temperatures and pests. You don’t have to worry about groundhogs like you would in the field, but the tiniest of pests, thrips and spider mites, can prove devastating.
As an entomologist, the stressor that most interests me is pest pressure, so we are investigating whether mixtures of varieties can help reduce pest pressure. We just finished collecting data on aphid populations for an experiment with spring wheat and the bird cherry-oat aphid (Rhopalosiphum padi). We started with pots containing four wheat plants, either all of the same variety or four different varieties. We individually added three adults aphids to each plant and then assessed the aphid populations 7 and 14 days later. We were lucky enough that our days counting aphids in the greenhouse were not when the outdoor temperature was 90o+, but it was by no means pleasant. Everybody involved was amazing and we wrapped up data collection and counted many, many aphids with our little clicker counters: 23,090 the first week and 166,720 the following week. While I am well aware of the remarkable ability of the aphids to pump out clones of themselves, the numbers never cease to amaze me when I conduct an experiment like this. This is why they are pests.
In addition to studying the ability of genotypic diversity to manage the biotic stressor of pests, I am also beginning to work with abiotic stressors. My abiotic stressor of choice is water limitation (i.e. drought) because of the increased levels of drought crop fields will likely face with climate change. For experiments with drought and aphids, I will be using bird cherry-oat aphid again, but will shift to winter wheat. The main difference between spring and winter wheat is that winter wheat needs to be vernalized (exposed to cold weather) to produce seed. Thus far, we have primarily been screening a large pool of varieties for their resistance to aphids and to drought stress. This will allow us to choose a range of both aphid and drought resistances to include in our mixtures.
While sunny skies and warm weather make imposing drought easier, let’s all hope for non-extreme temperatures. The goal of these experiments isn’t to test the heat-tolerance of members of our lab.
- Ian Grettenberger (1 July 2013)