1a. Objectives (from AD-416):
The objective of the project is to improve genetic resources in Prunus by providing genomic information for peach accessions held at the National Center for Germplasm Resources (NCGR) in the form of short read sequences and linking this information to peach germplasm with enhanced water use efficiency. This information can be used for marker discovery using the genotyping by sequencing (GBS) protocol and association mapping to facilitate identification of markers linked to genes responsible for improved water use efficiency and/or drought resistance.
1b. Approach (from AD-416):
Peach germplasm held at NCGR will be analyzed using a combination of physiological measurements for water use and genotyping with the GBS approach. Water use efficiency will be screened initially with the shoot ash analysis procedure described by ARS SYs for fruit trees. Selected germplasm will then be analyzed for stable carbon isotope discrimination. Individuals exhibiting the highest and lowest water use efficiencies will be analyzed by GBS.
3. Progress Report:
Recent studies indicate that increased frequency of heat stress, droughts and floods negatively affect crop yields. Climate variability and change also modify the risks of pest and pathogen outbreak, negatively affecting food, fiber, and forestry. Drought tolerance/resistance has been listed as a second major environmental hazard, after freeze and frost injury, for stone fruit in Prunus Vulnerability statement. Adaptation to long term drought is controlled by complicated interactions between anatomy, physiology, and biochemistry, all of which are directly or indirectly under genetic control. One measure of adaptation to arid conditions is water use efficiency (WUE = the ratio of units of photosynthesis to units of plant water loss through transpiraton). Developing fruit trees with more efficient uptake, transport, and/or use of water could lead to the development of varieties more tolerant of drought. Peach [Prunus persica (L.) Batsch] is one of the most economically important fruit crops that, due to its small genome size, taxonomic proximity to other important agronomic species and short juvenile period, has become a model plant in genetic studies of fruit trees. This proposal has two objectives: 1) identify peach varieties with the best WUE and 2) correlate these varieties with changes in gene structure by sequencing large sections of the genome from these individuals. We have screened 265 varieties of peach using ash analysis (negative correlates with the more expensive method of stable carbon isotope analysis) and have selected the most efficient water users for sequencing and further confirmation by isotope analysis. The sequencing data is currently being processed for identification of select genes and determination of difference that may contribute to improvement of water use. Select individuals can also be tested for drought tolerance in the greenhouse or growth chamber.