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


2016 Annual Report

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].

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.

Progress Report
This is a new project which began on June 15, 2016. We have achieved the first step to meeting objectives; we acquired seeds of various cultivars of diploid strawberry Fragaria vesca. We will be propagating this material under controlled conditions to generate clones for salt tolerance experiment. We have also initiated experiments to make crosses between alfalfa genotypes with different salt tolerance mechanisms. In last few weeks, we have generate selfed crosses of 12 alfalfa genotypes. To consolidate and strengthen complementary research, a National Program 211, Water Availability and Water Management project, 2036-13210-010-00D, “Crop Genetic Improvement and Crop Management in Irrigated Areas Affected by Salinity and Toxic Ions” was redirected to NP 301 Plant, Microbial and Insect Genetic Resources, Genomics, and Genetic Improvement. For more information, please see the report for this previous project that terminated on June 14, 2016.



Review Publications
Sandhu, D., Atkinson, T., Noll, A., Johnson, C., Espinosa, K., Boelter, J., Abel, S., Dhatt, B.K., Singsaas, E., Sepsenwol, S., Goggi, S., Palmer, R. 2016. Soybean proteins GmTic110 and GmPsbP are crucial for chloroplast development and function. Plant Science. 252:76-87 doi: 10.1016/j.plantsci.2016.07.006.