Nitrogen-fixation drought tolerance in virginia-type peanut

Abstract

ABSTRACTSymbiotic nitrogen-fixation activity of grain legumes commonly does not exhibit tolerance to soil drying, including in peanut (Arachis hypogaea L.). Since the demand for nitrogen of peanut is large in the synthesis of seeds with high protein concentration, loss of nitrogen-fixation activity can result in major yield decreases. The objective of this study was to search the germplasm of virginia-type peanut for sources of nitrogen-fixation drought tolerance. The first phase was a field screen in one growing season of 100 lines from which leaves were harvested and nitrogen concentration measured. Research in soybean had shown that low leaf-nitrogen concentration was associated with nitrogen-fixation drought tolerance. A wide range of leaf nitrogen concentrations was observed, and 10 lines of low leaf nitrogen (23.1 to 26.4 mg N g−1) were identified for the second phase of study. The second phase of study was done in a greenhouse with 5-week old plants sealed in pots subjected to a 2-week dry down. Each day, the plants were briefly exposed to acetylene to measure acetylene reduction activity as an indicator of nitrogen-fixation activity. The soil water content, at which a decline in nitrogen fixation was initiated, was not different among seven lines. Three of the lines exhibited high sensitivity of nitrogen fixation to soil drying. None of the lines, however, exhibited substantial tolerance of nitrogen fixation to soil drying, indicating a need to search an even more diverse population of peanut to identify a genetic source for tolerance.