|King, A - UNIVERSITY OF ARKANSAS|
|Purcell, L - UNIVERSITY OF ARKANSAS|
Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2003
Publication Date: October 15, 2003
Citation: King, A., Purcell L.C., Sinclair, T.R., Nelson, R. 2003. Screening Maturity Group IV Soybean Plant Introductions for Drought-Tolerant Dinitrogen Fixation [abstract][CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting, November 2-6, 2003, Denver, CO. Technical Abstract: N2 fixation in soybean decreases with moderate soil drying. Shoot ureides, products of N2 fixation, are reportedly negatively correlated with genotypic differences in sensitivity of N2 fixation to water deficits. From 1995 to 1998, petiole ureide levels were determined for MG IV plant introductions (PI) from the soybean germplasm collection in Urbana, IL. Eighty PI with low ureides (0 to 5 µmol/gdw) and eight PI with high ureides (46 to175 µmol/gdw) were evaluated for shoot biomass and N accumulation and shoot ureide concentration during a progressive water deficit in a field study in 2000. Nine PI were identified as potentially tolerant and six as sensitive to drought, with one PI in each group having high ureides in the original screen. There was no correlation between shoot ureide level and biomass or N accumulation in the field. In the growth chamber, nitrogenase activity (acetylene reduction assay) was measured in response to soil drying for the 15 sensitive or tolerant lines. Drought-sensitive cultivar >KS4895' was included as a check. Five PI had drought-tolerant and one had drought-sensitive N2 fixation relative to KS4895. The drought-sensitive PI was the high ureide PI (58 µmol/gdw) that was identified as potentially sensitive in the field experiment. Studies are underway to investigate the physiological basis of differences in sensitivity among these lines and to incorporate drought-tolerant N2 fixation into commercial germplasm.