Heritability of N₂ Fixation Traits, and Phenotypic and Genotypic Correlations between N₂ Fixation Traits with Drought Resistance Traits and Yield in Peanut

Abstract

Drought stress reduces growth and yield in peanut (Arachis hypogaea L.) and also reduces nitrogen fixation (NF). Peanut production in drought prone areas should be enhanced by the development of cultivars that can fix more nitrogen (N) under drought conditions. The aims of this study were to estimate heritability for NF and to estimate phenotypic and genotypic correlations among traits related to NF with drought‐resistance traits and yield under well‐watered and drought conditions. A total of 140 lines in the F4:7 and F4:8 generations derived from four crosses, parental lines, and a non‐nodulating line as a non‐N2‐fixing reference plant were evaluated in the dry seasons 2005/2006 and 2006/2007. These lines were evaluated in rhizobium inoculated soil without N fertilizer under field capacity (FC) and 2/3 available soil water (AW). Data were recorded for specific leaf area (SLA), SPAD chlorophyll meter reading (SCMR), nodule number (NN), nodule dry weight (NDW), shoot dry weight (SDW), pod dry weight (PDW), total dry weight (TDW), harvest index (HI), and NF. Broad‐sense heritability (h2b) and narrow‐sense heritability (h2n) estimates for NF under FC and 2/3 AW were in the same ranges (h2b = 0.84 to 0.98 and h2n = 0.29 to 0.39). Positive relationships between NF under FC and 2/3 AW (r = 0.73, P ≤ 0.01) indicated that selection for the lines that fixed high N under well‐watered conditions should produce lines that fixed high N under drought conditions. Selection for NF under drought conditions might be more effective in improving yield because of a higher correlation between NF and PDW (rG = 0.43, P ≤ 0.01) under drought conditions than under FC (rG = 0.13). The use of SCMR and SLA as surrogate traits for NF would be less effective than direct selection because of weak correlations between these traits and NF.

Effects of salt stress and rhizobial inoculation on growth and nitrogen fixation of three peanut cultivars

“…1). Peanut shoot dry weight can be considered a valid yield indicator, as positive correlations with pod dry weight and also N fixation have been reported under water deficit conditions (Pimratch et al. 2009).…”

“…1A). Significant positive correlations found between N fixation, shoot dry weight and pod dry weight under water stress have led to proposed selection for high N fixation as a way to enhance peanut yield under water‐limited conditions (Pimratch et al. 2009).…”

“…1). Peanut shoot dry weight can be considered a valid yield indicator, as positive correlations with pod dry weight and also N fixation have been reported under water deficit conditions (Pimratch et al 2009). Non-inoculated Jambo plants were little affected by salinity, and their shoot dry weight tended to increase upon salt stress exposure.…”

Legumes in the reclamation of marginal soils, from cultivar and inoculant selection to transgenic approaches

“…Classical heritability studies of selected traits are also ongoing (Pimratch et al 2009) and new molecular techniques, such as microsatellite characterization (Lazrek et al 2009) and transcriptome and proteome studies, will help to better classify and characterize tolerant and sensitive legume cultivars.…”

Response of growth and nitrogen fixation to pod elimination of three annual Medicago species submitted to drought and subsequent recovery

“…Three species of annual Medicago, M. rigidula, M. scutellata, and M. polymorpha were used in 87 this study. The rate of 300 mg bacteria per 60 kg of seed was used(Pimratch et al, 2008). After incubation, pods were removed from half 89 of the seeds for the treatments assigned to "without pods".…”