With global climate change, temperatures are expected to increase and precipitation is expected to decrease in some agricultural areas. Consequently, crops in these areas will need irrigation, but irrigation can cause higher soil salinity. As a first step towards engineering crops that are resistant to salt stress, we are studying the genetic architecture underlying salt stress in Brassica rapa. While some varieties of B. rapa are grown for their large edible leaves, other varieties are grown for their oil seeds. Taller plants may benefit oil seed production, but plant height can be inhibited by salt stress. In order to investigate the effects of salt stress on plant morphology, we conducted a greenhouse experiment with nearly 200 genotypes of B. rapa. We watered different plants with the same genotype with either tap water or water containing a low concentration of salt. Throughout plant development, we measured height and leaf number and then calculated the mean height to leaf number ratio for each of three developmental phases. We found an interaction between treatment (salt/control) and developmental phase in which this ratio was lower for plants in the salt condition than those in the control condition later in development. This interaction may indicate a tradeoff between competitive flowering and photosynthetic efficiency in response to salt stress. We also conducted quantitative trait loci analyses in order to identify locations along the B. rapa genome that may explain variation in height to leaf number ratio late in development. This analysis revealed several interesting loci along the genome that may form the basis of future genetics research. Identifying plant-environment interactions and their underlying genetic architecture can lead to crop improvements especially for agricultural areas affected by global climate change.
Authors: Eastyn Newsome, Ryan Gerbitz, Indi Saxena, Wolfgang Graff
Faculty Advisor: Robert Baker, Department of Biology
Graduate Student Advisor: Tyler Thrash, Department of Biology
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