The 2012 ASHS Annual Conference

Water is the most limiting resource in the environment. During episodes of drought, crop losses can be substantial due to both direct and indirect effects of dehydration. Even irrigation alternatives are not entirely satisfactory towards solving this problem due to their expense and to competition for urban water needs. It is therefore urgent that drought resistant and/or more water use efficient crops be identified or developed. Fruit trees are particularly difficult to monitor in the long term because of the limitations associated with most drought measurements. We have used suppression subtractive hybridization (SSH) to identify genes from apple root, bark and stem responding to simulated drought (40% of full saturation) and subsequent recovery. Very few genes identified as up- or downregulated in response to treatment overlapped between treatments.  In addition, very few genes overlapped betweem tissue. In order to understand more fully the mechanisms associated with fruit tree defense against dehydrative stress, we compared expression of select genes in root, bark, and leaf tissue from treated plants and their well- watered controls. Similarly, comparisons involving drought-recovery conditions were made, involving the resumption of normal watering of plants which had been maintained in drought-simulated conditions. The results demonstrate the importance of applying different approaches to analyze the transcriptome and to emphasize gene expression differences in tissues in response to drought.