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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetic Improvement of Crop Plants for Use with Low Quality Irrigation Waters: Physiological, Biochemical and Molecular Approaches

Location: Water Reuse and Remediation Research

Project Number: 2036-13210-011-00-D
Project Type: In-House Appropriated

Start Date: Jun 15, 2016
End Date: Mar 11, 2018

Objective:
Objective 1: Characterize plant responses to salt stress and isolate important genes associated with salt tolerance [NP301, C1, PS 1A]. Objective 2: Evaluate and develop germplasm with increased tolerance to salt stress [NP301, C1, PS 1A].

Approach:
This project will focus primarily on two important California based crops, alfalfa and strawberry. Alfalfa is moderately tolerant to salinity, while strawberry is very sensitive to salt. Objective 1. We propose to dissect salt tolerance mechanism into its components and add genetic, physiological and biochemical tools to our selection approach, which earlier considered only biomass production and ion accumulation. For crops such as alfalfa that are polyploid and highly heterozygous, it is important to reduce variation by developing clonal material. We plan to use this alfalfa clonal material for the physiological, biochemical and genetic studies and study long term response to salt stress. We also propose to determine the levels of total phenolics, antioxidant capacity, quantification of photosynthetic activity, stomatal conductance, and use these biochemical/physiological indicators to characterize genotypes that are tolerant to high salt concentrations. We have identified 20 genes from the model plants such as Arabidopsis that are involved in different components of salt tolerance mechanism including i) ion efflux from root to soil, ii) ion accumulation in vacuoles, iii) retrieval of ions from xylem, iv) increased tissue tolerance to high concentrations of toxic ions and accumulation of compatible solutes. Strawberry genome has been sequenced, so homologs of Arabidopsis genes can be easily identified. For alfalfa that has not been sequenced, RNA-seq atlas can be used to design primers for PCR. We propose to study expression of these 20 genes in roots and leaves of the control and salt stressed plants using quantitative Reverse Transcription – PCR (qRT-PCR). Based on the correlation between salt tolerance index and expression profiles of genes involved in different components of salt tolerance mechanism, major genes that play important role in salinity stress will be identified. This analysis will not only help us in determining relative importance of different components of salt tolerance mechanism but will also facilitate identification of genes that can then be used to screen alfalfa and strawberry germplasms for salt tolerance. Objective 2. Expression analysis of genes will allow us to classify genotypes based on their ability to regulate different components of salt tolerance mechanism. For example, a genotype may be really good in excluding Na+ from root to soil but may not be as good in tissue tolerance to excessive sodium in the leaf tissue. We propose to make crosses between selected genotypes to combine different components of salt tolerance. Segregating populations will be subjected to physiological studies to select individual plants with enhanced salt tolerance. Gene expression analyses will be performed on these selected plants to confirm presence of multiple components of salt tolerance mechanism. This knowledge will be particularly important for breeders and geneticists in isolating genes or quantitative trait loci (QTL) important in salt tolerance. In addition, some of the salt tolerant genotypes developed and evaluated in this project may be integrated by alfalfa and strawberry breeders in their breeding programs.

Last Modified: 09/22/2017
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