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United States Department of Agriculture

Agricultural Research Service

Research Project: Crop Genetic Improvement and Crop Management in Irrigated Areas Affected by Salinity and Toxic Ions
2013 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.


3.Progress Report:
This report documents the progress during the first 18 months of this project. All but one of the 12 month milestones were completed and good progress has been made on the 24 month milestones. Five commercial cultivars of strawberry were acquired in October 2012 and planted outdoors at the Salinity Laboratory. After plant establishment, four levels of salinity were applied daily with irrigation water with three replicates of each treatment. Fruit production was recorded from January to June 2013. In June, plant samples were collected for major ion and micro nutrient analyses as well as antioxidant activity analyses in response to salinity of irrigation water. In June, we also collected soil samples from each treatment and prepared for electrical conductivity (EC), pH and major ion analyses of the saturation extracts. Plant canopy, root biomass and gas exchange measurements were also recorded during the experiment to evaluate cultivar tolerance to salinity. Significant differences in salt tolerance were established; cultivars with greater production under non-saline conditions maintained increased productivity under saline conditions. Twenty wild type strawberries from different countries were selected and ordered based on native climatic conditions. These plants are currently being propagated to generate enough plants for future salinity tolerance experiments.

We completed the ion analyses of plant samples from the outdoor alfalfa study conducted last year, performed statistical analysis of the data and prepared a manuscript draft. Plant samples from two seasons are being for their antioxidant capacity. Samples are currently being analyzed for their nutritional value for ruminant feed to determine if salinity affects nutritional value of this important forage. We completed a large greenhouse alfalfa germination study and an additional salt tolerance study under varying salinity and water composition with 15 geneotypes (7 from Argentina). We examined alfalfa production during 10 cuttings over 12 months, and made measurements of photosynthesis, respiration, stomatal conductance and other physiological parameters. We have collected samples and completed analysis of shoot ion composition during two seasons. We have collected material for analysis of secondary metabolites and root ion composition. We have also collected genetic material for further evaluation.

We initiated a rice study in the greenhouse, examining the interactive effects of elevated pH, salinity and nitrogen on plant biomass and rice grain yield. We pretreated the soils with varying levels of salinity and pH to achieve the target values in the soil. We examined 3 salinity levels (EC 2, 6 and 10), 3 pH levels (7, 8 and.
9)and three nitrogen levels (one optimal and two suboptimal), with three replications per treatment (81 total containers). We recorded total dry weight, shoot weight, number of tillers and panicles, grain weight and other physiological parameters. Data is being analyzed.


4.Accomplishments
1. Screening alfalfa varieties for salt tolerance. Determination of salt tolerance is an important consideration when selecting varieties for field planting. Typically, varietal tolerance to salinity has been done based on tolerance during germination. Our research indicated no relationship between germination success of alfalfa varieties under elevated salinity and their biomass production under saline conditions. These results indicate that salt tolerance of alfalfa needs to be conducted with evaluation at least through the seedling stage. Farmers will directly benefit from germplasm selection for planting under saline conditions if they have accurate knowledge of varietal salt tolerance information.


Review Publications
Ha, W., Suarez, D.L., Lesch, S.M. 2013. Predicting perchlorate uptake in greenhouse lettuce from perchlorate, nitrate and chloride irrigation water concentrations. Journal of Environmental Quality. 42:208-218.

Semiz, G.D., Unlukara, A., Yurtseven, E., Suarez, D.L., Telci, I. 2012. Salinity impact on yield, water use, mineral and essential oil content of fennel (Foeniculum vulgare Mill.). Journal of Agricultural Science. 18:177-186.

Smith, T.E., Grattan, S.R., Grieve, C.M., Poss, J.A., Lauchli, A.E., Suarez, D.L. 2013. pH dependent salinity-boron interactions impact yield, biomass, evapotranspiration and boron uptake in broccoli (Brassica oleracea L.). Plant and Soil. DOI: 10.1007/s11104-013-1653-9.

Last Modified: 8/19/2014
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