Project Number: 2036-13210-012-006-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Apr 1, 2020
End Date: Dec 31, 2023
Objective 1: Evaluate elite rootstocks from breeding populations for salinity tolerance. Objective 2: Identification of novel sources of salinity tolerance by screening 50 diverse parental lines from Prunus germplasm.
Objective 1: In 2020-21, we will evaluate up to 38 rootstocks (provided by Dr. Gradziel and Dr. Aradhya) in three replications (three plants per replication) in a randomized block design. Screening for salinity will be conducted in the field at the US Salinity Laboratory in Riverside CA. For our treatment we will use mixed ion composition to represent a range of natural water compositions, with Na as the main cation and Cl as the main anion. Control treatment will be basic ½-strength Hoagland’s nutrient solution containing essential macro- and micronutrients. After transplanting into 2-gallon pots, plants will be allowed to acclimatize for four weeks. We will focus on screening genotypes at moderate salinity levels (EC = 3 dS/m). Pots will be irrigated to a target leaching fraction of 0.3. Leaf samples will be taken four weeks after the initiation of treatment to determine tissue ion composition. Tissue samples will be dried, digested and analyzed to determine the concentration of major and minor elements. Plants will be assessed for height and trunk diameter before and after treatment and these parameters will be related to their Na and Cl tissue accumulation to establish salinity tolerance. We will evaluate the association of salt tolerance with leaf chloride and sodium content. From the results of 2020-21 trials, the top 10 hybrids will be selected. These selected hybrids, along with additional dozen new hybrids from Drs. Gradziel’s and Aradhya’s breeding programs will be evaluated in 2021-22. This second-year evaluation will allow us to find few top performing hybrids for salinity tolerance. Relation of salinity-tolerance data with other traits such as vigor, disease and nematode resistance will help in selecting hybrids with multiple superior traits that can be commercialized in a short-time span. Objective 2: In addition to screening of breeding material in Objective 1, we propose to test salinity tolerance of 50 diverse parental species from Prunus germplasm collection for rootstock breeding (also provided by Dr. Gradziel and Dr. Aradhya). The parental species will be selected based on species identified as salt tolerant in previous publications and unpublished research. Individual genotypes within these species and species crosses showing good combining ability (desirable root architectures, vigor, boron tolerance, etc.), and tolerance to nematodes (root knot, lesion, and/or ring) will be selected. Plants will be exposed to 2 salinity levels (1.4 and 3.0 dS/m) in 2021-22 and the selected lines will be reevaluated in 2022-23. In saline treatment, we will use a mixed-salt water composition to achieve target EC = 3.0 dS/m. Pots will be irrigated to a target leaching fraction of 0.3. Leaf samples will be taken four weeks after the initiation of treatment to determine tissue ion composition. Tissue samples will be analyzed for macro and micronutrients. Data will be recorded for trunk diameter and survival rate. Association between tissue ion concentrations and change in trunk diameter and survival rates will be determined as a parameter to evaluate tolerance to Na+ and Cl- toxicity.