Date of Award
12-17-2015
Document Type
Thesis
Degree Name
Environmental Sciences, MS
First Advisor
Argelia Lorence
Committee Members
Ana McClung; Erik Gilbert; Gregory Phillips
Call Number
LD 251 .A566t 2015 G52
Abstract
Rice is economically, culturally, and socially important to many people in the world. Arkansas is the main rice producer in the USA. Climate change continues to increase the incidence of abiotic stresses such as cold, heat, drought, water excess, and soil salinity. These stresses pose a particular challenge to rice cultivation. Rice has lower yields under cold stress, particularly when plants are exposed to cold at the seedling and reproductive stages. Early spring plantings and field irrigation with underground cold water expose rice seedlings to cold stress. Previous studies in Arabidopsis thaliana have shown that lines engineered to have elevated vitamin C (ascorbate, AsA) content are tolerant to multiple abiotic stresses including cold. We hypothesized that foliar ascorbate content increases in response to cold stress in rice seedlings. To address this hypothesis we studied the role of ascorbate content at the seedling stage as a response to cold stress in tolerant and sensitive rice (mPing) lines. The mPing lines are segregating for a transposable element called mPing that is related to abiotic stress response. mPing lines significantly increased foliar ascorbate content when exposed to cold stress. However this increase was not associated with the cold tolerance response observed in a previous study evaluated at the germination stage. Our findings indicate that ascorbate plays a role in the cold-stress response, independent of the cold tolerance at the germination stage. Our second hypothesis is that the broad genetic diversity of the Rice Diversity Panel 1 (RDP1) is associated to significantly different levels in foliar ascorbate content. We evaluated the RDP1 to identify accessions with high and low foliar ascorbate content, and associated those to cold tolerance. Under normal conditions, foliar ascorbate varies significantly among the RDP1 accessions, revealing that the genetic variability present in the RDP1 is associated to significantly different levels in foliar ascorbate content. To assess the correlation of this variability with cold tolerance we exposed the accessions with significantly different AsA content from a standard AsA control to cold stress. Two out of three (66.7%) high AsA accessions were cold tolerant, whereas only three out of nine (33%) low AsA accessions were cold tolerant, as established by coleoptile length reduction. This 2-fold difference (66.7% vs. 33%) indicates a positive effect between high AsA content and cold tolerance. While high AsA content is not the only factor in establishing cold tolerance, our results show that ascorbate supports this tolerance. The final part of this research associated the results of foliar ascorbate content by subpopulation using genome wide association studies (GWAS).This analysis indicate that hits in chromosome 5 and 2 are promising genomic regions that can be further studied to identify candidate genes involved in synthesis, degradation, or regulation of ascorbate content in rice.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Castillo Gonzalez, Sonia Elizabeth, "Assessing Foliar Ascorbate Content in a Rice Diversity Panel and In Selected Mapping Population Lines with Varying Levels of Seedling Cold Tolerance" (2015). Student Theses and Dissertations. 697.
https://arch.astate.edu/all-etd/697
