Differential Physiological and Metabolic Responses to Drought Stress of Peanut Cultivars and Breeding Lines

Abstract

The Virginia–Carolina region is the most important peanut (Arachis hypogaea L.) production region for the large‐seeded, virginia‐type peanut in the United States, but 85% of the production is rainfed and predisposed to water deficit stress. The mechanisms virginia‐type peanut uses in response to drought stress are poorly understood. We evaluated several physiological and metabolic characteristics and their relationship with pod yield in eight virginia‐type cultivars and advanced breeding lines in rainfed and irrigated field trials in 2011 and 2012. Each year, evaluations were performed at three sampling dates in conjunction with growth stages beginning flower, pod, and seed. Significant (p ≤ 0.05) genotypic variation in membrane injury, chlorophyll fluorescence (Fv/Fm ratio), and relative levels of metabolites and lipid‐derived fatty acids was observed in response to water regime and sampling time. In general, in both years, the Fv/Fm ratio, organic acids, and fatty acids decreased in rainfed vs. irrigated plants, while the relative levels of sugar and cyclic polyols increased. Because higher levels of organic acids and lower levels of sugars were associated (p ≤ 0.05) with higher pod yield, we conclude that natural stress responses rather than adaptive mechanisms to drought prevailed for the genotypes used in this study. Based on its minimal changes in the Fv/Fm ratio and metabolite levels of the rainfed vs. irrigated plants, line SPT 06‐07 showed improved tolerance to water deficit stress; this line can be an important source for drought tolerance improvement of the virginia‐type peanut.

Heat Stress Related Physiological and Metabolic Traits in Peanut Seedlings

“…For example, major organic acids including, ascorbate, shikimate, and quinate showed significant decreases in their relative steady-state levels in heat-stressed seedlings, especially during the last two time-points (Days 4 and 7). Similar results were reported in drought-stressed wheat (Bowne et al, 2012) and field grown mature peanut plants (Singh, 2013). However, fumarate, malate, tartrate, citrate, and threonate increased either throughout entire heat stress exposure or in the first days of heat stress.…”

“…The uniqueness of SPT 06-07 in comparison with the other genotypes was also shown by the step-wise variable classification analysis, where SPT 06-07 was selected as the sole genotype of Group II, which was significantly different from Group I, that included the remaining genotypes. SPT 06-07 has exhibited improved drought tolerance of mature plants in field studies (Singh, 2013;Singh et al, 2014). Further, this shows that SPT 06-07 could be an important source for improvement of peanut tolerance to heat and drought stress at multiple growth stages.…”

“…Even though we were able to highlight some metabolites, e.g., hydroxyproline, galactinol, and pinitol, that could explain specific differential physiological (F v /F m ratio and MI) responses in peanut plants, overall our data suggested general stress responses by seedlings rather than adaptive mechanisms under heat stress. Among the cultivars, Bailey seedlings seemed to have better tolerance to early season heat stress; MI was low (Table 2) and the F v /F m change due to the heat exposure was significantly less than for other genotypes (Singh, 2013). At least in part, this may explain the good crop stand and high yields observed in farmer fields for this cultivar, grown on over 85% peanut acreage in the VC region.…”

“…Virginia-type peanut cultivars (CHAMPS, Bailey, and Phillips) and advanced breeding lines (N04074FCT, N05006, N05008, N05024J, and SPT 06-07) were selected for this experiment. They were selected based on their differential response to reduced soil moisture in the field, therefore potentially different response to heat (Singh et al, 2014). Seeds were surface sterilized with 70% ethanol for 1 min and rinsed twice with sterile water.…”

Metabolite Profiles of Raw Peanut Seeds Reveal Differences between Market‐Types

“…The field of metabolomics aims to identify as many small molecular-weight compounds as possible using untargeted analyses (Cevallos-Cevallos, Reyes-De-Corcura, Etxberria, Danyluk, & Rodrick, 2009). Metabolomic analyses usually provide qualitative data, to illustrate the relative differences in amounts of certain compounds as a result of subjecting the object of study to different treatments (Almstetter, Oefner, & Dettmer, 2012;Cevallos-Cevallos et al, 2009;Singh et al, 2014). These include those small molecular-weight compounds that are the result of secondary metabolism.…”