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ARS Home » Pacific West Area » Riverside, California » Agricultural Water Efficiency and Salinity Research Unit » Research » Research Project #445043

Research Project: Evaluating New Breeding Material for Salinity Tolerance in Almond Rootstocks and Exploring Novel Sources of Salinity Tolerance in Prunus Germplasm

Location: Agricultural Water Efficiency and Salinity Research Unit

Project Number: 2036-13210-013-006-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Aug 1, 2023
End Date: Jul 31, 2027

Objective 1: Screen elite breeding lines and cultivar lines for salinity tolerance. Objective 2: Evaluate elite breeding lines for quantitative responses to drought and salinity stress parameters.

Objective 1: Screening results from our current project led to the identification of parental combinations that result in the most salt-tolerant hybrids. Based on these results, breeders will generate additional hybrids for future screening. We intend to screen between 30 and 40 rootstock hybrids for salinity tolerance each year, including some cultivar lines that are in regional variety trials. The rootstocks will be grown in 3-gallon pots in three replications (three plants per replication) in a randomized block design. Control treatment will be basic ½-strength Hoagland’s nutrient solution containing essential macro- and micronutrients. We will screen genotypes at moderate salinity levels (EC = 4 dS/m) as almonds are sensitive to salinity. Leaf samples will be taken four weeks after the initiation of treatment to determine tissue ion composition. Plants will be assessed for trunk diameter at the beginning of the experiment and 10-months later at the end of the experiment, and the change in truck diameter will be calculated. In addition, the survival rate will also be recorded. The survival rate and the trunk diameter will be associated with their Na and Cl tissue accumulation to establish salinity tolerance. We will evaluate the association of salt tolerance with leaf chloride and sodium content. The experiment will be continued for three growing seasons, 2023-24, 2014-25, and 2025-26. From the first growing season results, the top 10 hybrids will be selected — these selected hybrids, along with additional new hybrids from Drs. Gradziel’s and Kluepfel’s breeding programs will be evaluated in the second growing season. A similar setup will be used for the second and third growing seasons. Relation of salinity-tolerance data with other traits such as vigor, disease, and nematode resistance will help select hybrids with multiple superior traits that can be commercialized quickly. Objective 2: The experiment will be conducted on almond rootstocks planted in 3-gallon pots in the field in the growing season 2025-26. Ten selected rootstocks from the previous year’s screening will be evaluated for combined drought and salinity stresses. The experiment will evaluate the effect of three irrigation water salinities with EC of 0.7 dS m-1, 3.5 dS m-1, 4.5 dS m-1, designated S0, S1, and S2, respectively, and two water treatments 100% and 75% of ETc, designated D0 and D1, respectively. Water consumption will be determined by measuring changes in soil water content. Using a soil moisture probe, we will calibrate the soil before and after irrigation to ensure that the probe is accurately measuring water content. After that, we may use the probe measurements instead of weighing the pots to determine water content and calculate water to be applied. Parameters to be studied include survival rate, trunk diameter, and leaf ion concentration (as described in objective 1). Trunk diameter data will be analyzed using SAS/STAT software package. Information on salinity tolerance of different parental lines will be beneficial to research breeding programs, as these lines can be crossed to develop new salt-tolerant hybrid rootstocks.