|Pimratch, S - KHON KAEN UNIVERSITY|
|Jogloy, S - KHON KAEN UNIVERSITY|
|Vorasoot, N - KHON KAEN UNIVERSITY|
|Toomsan, B - KHON KAEN UNIVERSITY|
|Kesmala, T - KHON KAEN UNIVERSITY|
|Patanothai, A - KHON KAEN UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2009
Publication Date: May 15, 2009
Citation: Pimratch, S., Jogloy, S., Vorasoot, N., Toomsan, B., Kesmala, T., Patanothai, A., Holbrook Jr, C.C. 2009. Heritability of N2 fixation traits, and phenotypic and genotypic correlations between N2 fixation traits with drought resistance traits and yield in peanut under different water regimes. Crop Science 49:791-800. Interpretive Summary: Unpredictable rainfall creates drought stress which reduces the yield of peanut in areas throughout the World. This drought stress also reduces nitrogen fixation in peanut. Breeding peanut varieties with enhanced nitrogen fixation under drought stress should result in greater yields. The objective of this study was to determine the feasibility of breeding peanut with enhanced nitrogen fixation under drought stress. Four segregating breeding populations were evaluated under well-watered and under drought condition to estimate the heritability for nitrogen fixation. Heritability estimates were moderately high under both stressed and non-stress conditions, indicating that it should be possible to select for improved nitrogen fixation. Positive relationships were observed between nitrogen fixation under both conditions indicating that selection for nitrogen fixation under well-watered conditions should produce lines that fixed high nitrogen under drought conditions. However, selection for nitrogen fixation under drought conditions might be more effective in improving yield because of a higher correlation with yield than under well-watered conditions.
Technical Abstract: Drought stress reduces growth and yield in peanut and also reduces nitrogen fixation (NF). Peanut production in drought prone areas should be enhanced by the development of cultivars that can fix more 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 non-N2 fixing reference plant were evaluated in the dry seasons 2005/2006 and 2006/2007 in rhizobium inoculated soil without N fertilizer under FC and 2/3 AW. Data were recorded for SLA, SCMR, NN, NDW, SDW, PDW, TDW, HI and NF. Heritability 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**) 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 (rG = 0.43**) than under FC. The use of SCMR and SLA as surrogate traits for NF would be less effective than direct selection because of weak correlations.