Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 2011
Publication Date: July 1, 2011
Citation: Bassett, C.L., Glenn, D.M., Forsline, P.L., Wisniewski, M.E., Farrell, Jr., R.E. 2011. Characterizing water use efficiency (WUE) and water deficit responses in apple (Malus x domestica Borkh. and Malus steversii Ledeb.) M. Roem. HortScience. 46:1079-1084. Interpretive Summary: Frequent drought events have been predicted for the near future as a result of global warming. Dehydration is also an aspect common to other types of environmental stress, such as heat and freezing. Tree crops, like apple, are weakened with each event causing them to become more susceptible to disease and insect damage. We describe in this paper features of a commercial apple variety and Malus sieversii (wild ‘cousin’ of the cultivated apple) that relate to drought resistance. The wild apple species can provide genetic diversity to help us identify genes that are associated with drought and dehydration resistance. Transfer of these genes through standard breeding should result in enhanced drought tolerance of desirable apple varieties.
Technical Abstract: Reduced availability of water for agricultural use has been forecast for much of the planet. This is due in part to global warming, which has contributed to numerous cycles of drought worldwide, and due in part to greater urban demand for water in large metropolitan areas. Strategic improvement of water use efficiency (WUE) and drought tolerance in perennial crops, like fruit trees, could reduce water use without compromising yield or quality. We studied water use in apple trees using ‘Royal Gala’, a relatively water use efficient cultivar, as a standard. To examine whether or not genes useful for improving WUE are represented in a wild relative genetically related to M. × domestica, we surveyed Malus sieversii for traits associated with WUE and drought tolerance utilizing material collected from xeric sites in Kazakhstan. One such collection has been maintained in Geneva, NY, and surveyed for various phenotypes, as well as simple sequence repeats (SSRs). These data suggest that most of the diversity in this population is contained within a subpopulation of thirty-four individuals. Our results indicate considerable diversity in this group with respect to WUE and transpiration, while other traits such as leaf number, leaf size and stomata size, and density show little overall differences. These results imply that some of the genetic diversity is associated with changes in the biochemistry, uptake and/or transport of water, carbon, or oxygen that have allowed these trees to survive in water-limited environments.