Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Yajun Wu


Alfalfa (Medicago sativa), being a leguminous, highly fibrous, and proteinaceous plant has always been one of the top choices for the forage production but has high cost of irrigation in many dry and warm areas such as California and Arizona. Thus, a reduction of irrigation by using the higher water use efficiency (WUE) varieties can help the growers in reducing the cost and is critical for sustainable agriculture production. WUE is closely related to water loss through transpiring stomata. A study in our lab reported that Riverside (RS) an alfalfa genotype that has naturized in the national grassland in South Dakota, showed a higher WUE, compared to various commercial varieties and collections. Further studies in the lab revealed that RS showed a greater stomatal sensitivity to ABA in closure. In this study we examined if the stomatal density in different genotypes could play a role in the WUE of the plant by having impact on stomatal conductance. Alfalfa exhibits high density of stomata on adaxial surfaces. We found that variations in stomatal densities among genotypes exist, but stomatal density did not show correlation with the stomatal conductance, a contributing factor to WUE, emphasizing on the importance of stomatal sensitivity to ABA for higher WUE. One of the families of ABA receptors, Pyrobactin resistant like (PYL) in Arabidopsis is found to play essential role in drought conditions. We hypothesized that homologs of PYL in alfalfa could be involved in regulating stomatal conductance and hence play an essential role in WUE of the plants. The current study involved identifying the PYL-like gene family in alfalfa and analyzing the change in gene expression levels during water stress conditions. The 15 identified MsPYL proteins showed conserved domains and ABA receptor properties with START-like sequences. We demonstrated that MsPYL9 gene shows upregulation in RS genotype while showing no change in AF, genotype with lower WUE. This suggests that possibly, MsPYL9 could be related with higher WUE of RS. For this study we used two germplasms of alfalfa, but an understanding of candidate genes correlated with better WUE will bring new insights and potentially help improving alfalfa production in dry areas.

Library of Congress Subject Headings

Alfalfa -- Water requirements.
Alfalfa -- Drought tolerance.
Alfalfa -- Genetics.
Plants -- Transpiration.
Plant physiology.
Water use.

Number of Pages



South Dakota State University



Rights Statement

In Copyright