1a.Objectives (from AD-416):
Characterize the physiological mechanism(s) of salinity tolerance in selected alfalfa lines by identifying how the plants cope with saline soils.
1b.Approach (from AD-416):
Three major salinity tolerance mechanisms in plants have been identified; salt secretion, exclusion and sequestration. It is hypothesized that salt-tolerant alfalfa may utilize one or more of these mechanisms. Detailed physiological analysis will be conducted to determine which mechanism(s) confer salinity tolerance to experimental lines of alfalfa. Alfalfas with contrasting salinity tolerance will be analyzed for salt gland formation, deposit of salt crystal on tissue surface, salt contents in different tissues and distribution of salt at the cellular and sub-cellular level. In addition, assays for oxidative stress and detoxification will also be performed.
During FY2013: The objective of this research is to characterize the physiological mechanism(s) of salinity tolerance in the selected alfalfa lines by identifying how the plants cope with saline soils. Physiological parameters, including total salt concentration in shoots and roots, relative water content, number of leaves, stem node elongation were also measured on alfalfa plants propagated in the greenhouse. Selected lines of alfalfa were tested to confirm their improved tolerance to salinity compared to their parental lines based on biomass production and other parameters. The selected line appeared to be the best among the three selection lines tested. The new line also showed better plant health as the other two selection lines. For example, it is able to maintain relative water content and it accumulates chlorophyll (based on chlorophyll content index measurement) instead of showing a decrease in chlorophyll content as their parental lines under salinity stress. All three selected lines showed much healthier root growth under salinity conditions based on both visual examination and root dry weight production, which leads to a greater increase in root/shoot (dry weight) ratio compared to their corresponding parental lines under salinity. These results indicate the roots may play an important role in salt tolerance in these selected lines.