2012 Annual Report
1a.Objectives (from AD-416):
Objective 1: Identify variability in physiological and biochemical response mechanisms associated with the use of saline waters on cultivars of selected agronomic or horticultural salt-sensitive crops and develop strategies to mitigate the negative effects of salts and toxic ions by making more effective use of the waters for crop production.
Objective 2: Identify genetic markers for qualitative and quantitative traits associated with physiological salt stress responses that impact agronomic or horticultural characters and that can be used to develop germplasm with improved salt tolerance.
1b.Approach (from AD-416):
Objective 1: We will conduct experiments on seed germination as related to water composition and salinity. We will evaluate germination rate of 20 alfalfa cultivars or populations, in the greenhouse, and then determine growth parameters and yield of 7 of these populations in the sandtank facility, four with expected salt tolerance and three regarded as more sensitive. Five salinity treatments of each water type (chloride and mixed anion) will be imposed. Data to be collected include seedling emergence, survival, yield, mineral analyses, and analysis of compatible solutes, carbohydrates, nitrogenous compounds and antioxidants and ion selectivity coefficients for plant uptake. We will identify and quantify physiological and biochemical traits in strawberry related to salt stress or ion toxicity. We will evaluate commercial varieties of unknown salt tolerance under both sulfate and chloride dominated waters of varying salinity. We will also obtain other Fragaria species as appropriate, and conduct comparable experiments. In addition to yield parameters, ion analyses of major and minor elements, we will also measure soluble carbohydrates, nitrogenous osmolytes and antioxidants.
Objective 2: In the greenhouse, seedling shoots of the model plant M. truncatula will be grown, salinity treatments imposed, plant material harvested and gene expression evaluated for selected salinity related genes identified by others. We will utilize quantitative real-time PCR (qPCR). We will also study gene expression levels in the model plant species Fragaria vesca. After initial identification of relevant genes related to salt stress in alfalfa, we will design a PCR primer array to facilitate salt tolerance screening of cultivars. Similar experiments will be conducted with the model species. As a second approach to identify genes involved in salt tolerance; we will use RNAseq method to get a comprehensive view of the whole transcriptome from normal and salt-stressed model plants. Subsequent RNAseq experiments will be conducted for selected cultivars of alfalfa and strawberry. Knowledge gained from qPCR and RNAseq analysis will be utilized to design qPCR arrays and to screen for salt tolerance. After selection of appropriate genes we will also examine the genetic material from varieties evaluated in Objective 1, based on information generated from the model plant studies and also evaluate usefulness of qPCR arrays for routine screening. Fragaria species, the diploid model system F. vesca, accessions of F. x ananassa, and strawberry cultivars will be grown with irrigation water compositions typical of degraded waters. Plant tissues will be analyzed for mineral ion analysis and secondary metabolite concentrations. Using two separate approaches (qPCR method to evaluate gene expression data and RNAseq technology to visualize transcriptome data) will aid in positive identification of genes putatively involved in salt tolerance. After identifying promising candidate genes, we will study expression of these genes in known salt tolerant cultivars of Medicago and Fragaria.
This report documents progress for the parent Project 5310-13210-010-00D Crop Genetic Improvement and Crop Management in Irrigated Areas Affected by Salinity and Toxic Ions which started December 2011 and continues research from Project 5310-13210-009-00D Salinity and Trace Element Management for Crop Production in Irrigated Agricultural Systems. This report documents the progress during the first 9 months of this project. Excellent progress has been made on the 12 month milestones. Objective 1 – Milestone.
1)Initiate and complete studies of alfalfa emergence and germination..
2)Initiate experiment to determine agronomic, physiological, biochemical traits in salt-stressed alfalfa. Objective 2 - Milestone.
2)Identify, locate, acquire, propagate alfalfa cultivars for genetic study. We initiated and completed the initial outdoor sandtank experiment with 4 U.S. alfalfa varieties under a range of salinities and are completing the analyses of the shoot ion composition, water use efficiency and photosynthesis data. We completed the germination study. We initiated a larger germination and salt tolerance study under varying salinity and water composition in the greenhouse with 15 varieties (7 from Argentina). We have collected samples for analysis of ion composition and secondary metabolites. Preliminary information indicates that there is no relationship between germination success of the varieties under elevated salinity and their biomass production under saline conditions. We also determined that the most tolerant varieties under chloride based salinity were not the most tolerant under mixed chloride-sulfate salinity.