Location: Forage and Range Research
Project Number: 2080-21000-018-10-I
Project Type: Interagency Reimbursable Agreement
Start Date: Oct 1, 2015
End Date: Aug 31, 2019
Objective 1: Develop diverse alfalfa populations to identity genes conditioning drought/salt tolerance traits. Objective 2: Develop molecular markers and strategies for selection of drought- and salt-tolerant alfalfa and breeding for superior varieties with drought and salt resistance.
Advanced breeding populations for drought and salt tolerance are also available in CoPI's Lab. Four cycles of selection have been completed for relative salt tolerance in alfalfa using the greenhouse method described by CoPI, et al. This recurrent selection scheme has resulted in two populations of alfalfa that will be utilized in this study that were selected for increased germination and plant growth in the presence of salt using the protocol described by Co PI et al. (2004). One population (SynAS) was derived from sativa-type dryland alfalfa cultivars and from cultivars previously reported to have some tolerance to saline conditions. The other population (BC79) was selected from a drought tolerant tetraploid falcata-type alfalfa. Prior to selecting for salt tolerance, the falcata BC79 population went through four cycles of recurrent selection for persistence and forage production under extreme drought conditions typical of the Great Basin Region of the Intermountain U.S. We will evaluate these drought- and salt-tolerant alfalfa populations in different field locations to determine relative forage production, fall dormancy, flowering date, seed production, forage quality and plant morphological and physiological traits including root length, root thickness, root penetration ability, drought resistance index, relative leaf water content, and osmotic adjustment of these lines compared with standard checks. We hypothesize that alfalfa genotypes will be identified from among these populations that would meet commercial standards for forage production under drought and saline conditions. In fall 2016, the 200 CO maternal half-sib families will be planted at Prosser, WA, and Logan, UT, according to a randomized complete block experimental design with three replicates. The families will be seeded field plots and include check cultivars, 'NuMex Bill Melton' and 'Wilson'. Field trials at both sites will be grown under deficit irrigation management to impose significant water stress on the alfalfa field plots. During 2017 to 2019, forage biomass will be measured on all plots. Immediately before each harvest, relative water content (RWC) will be measured to monitor alfalfa water status during each growing season. Forage samples will be collected to measure forage quality parameters using the NIRS instrument. To measure forage production under salt stress, a modification of Co PI et al. (2004) will be used. This will involve substituting the small cones described by Peel for much larger ones with eight times the soil capacity. The EC of the solution will be much lower 9.0 dS M-1 (3.5 SAR), which is sufficient stress to separate genotypes based on forage production without high mortality. Plants will be cut to a height of 5 cm at the onset of salt treatment and allowed to grow for five weeks and the resulting forage biomass harvested. This protocol can be repeated on the same plants by treating the plants with non-saline solution for one week and then repeating the salt treatment process. Excellent results have been achieved using this protocol.