Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2013
Publication Date: 8/1/2013
Citation: Devi, J., Rowland, D., Payton, P.R., Faircloth, W.H., Sinclair, T. 2013. Nitrogen Fixation Tolerance to Soil Water Deficit Among Commercial Cultivars and breeding Lines of Peanut. Field Crops Research. 149:127-132. Interpretive Summary: Legumes have the unique ability to fix atmospheric nitrogen, via symbiotic relationships with rhizobacteria, allowing them to grow with little or no nitrogen fertilizer. An important question, however, is the ability of grain legume species to sustain nitrogen fixation under water deficit. Even though the early reports on peanut nitrogen fixation indicated a substantial tolerance to soil drying, these results are based on a very limited number of genotypes. Agricultural productivity is most limited by water availability and this trend of declining water resources will continue in the future. Therefore, selection of genotypes for nitrogen fixation tolerance to drought is likely to be important to avoid an inadvertent increase in sensitivity to water deficit. The objectives of this study were to examine in the sensitivity of nitrogen fixation activity in diverse peanut genotypes from U.S. and Indian germplasm collections to initially characterize the level of diversity in stress tolerance and potentially identify tolerant germplasm for improving crop stress tolerance. Experiments were carried out under controlled conditions and field trials. Overall, this study highlighted two important features in peanut about nitrogen fixation sensitivity to soil drying. First, there are currently limited differences in sensitivity to soil drying among the tested commercial cultivars. Second, among the Indian breeding lines that had shown a wide range in sensitivity of nitrogen fixation to soil drying, there was a correlation in the sensitivity found in the greenhouse tests and the field experiments. ICGV 86015 showed the greatest tolerance to the field water-deficit regimes, which was consistent with the tolerance it exhibited in the greenhouse study. In general, the nitrogen fixation of the commercial cultivars was substantially tolerant of soil water-deficits, but there still appeared to be a possibility for increasing its tolerance to water-deficit conditions in commercial cultivars. These results offer encouragement that large numbers of genotypes might be screened under field conditions for nitrogen fixation drought tolerance by measuring the relative nitrogen accumulation ratio under water-limited conditions.
Technical Abstract: Peanut is often grown in the U.S. on sandy soil with limited water holding capacity. Since nitrogen fixation activity of other grain legume species, and some peanut cultivars, has been found to be especially sensitive to soil drying, this study was undertaken to examine a possible limitation in U.S. commercial cultivars. The first test was done in the greenhouse with ten commercial cultivars subjected to controlled soil drying. The only significant difference was that nitrogen fixation activity in Georgia 06G was more tolerant of soil drying than York. The second test was done in the field at two locations by exposing plots to limited water for several weeks. Nitrogen accumulation during this period was measured as an index of nitrogen fixation tolerance of limited water availability. No significant differences were found among the commercial cultivars. In addition to the commercial cultivars in the field study, several breeding lines from India which had been characterized for nitrogen fixation drought sensitivity in the greenhouse were included. Among these breeding lines, ICGV 86015 showed the greatest tolerance to the field water-deficit regimes, which was consistent with the tolerance it exhibited in the greenhouse study. In fact, among the Indian breeding lines that had shown a wide range in sensitivity of nitrogen fixation to soil drying, there was a correlation in the sensitivity found in the greenhouse tests and the field experiments. In general, the nitrogen fixation of the commercial cultivars was substantially tolerant of soil water-deficits, but there still appeared to be a possibility for increasing its tolerance to water-deficit conditions in commercial cultivars.