Submitted to: Photosynthetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 12, 2006
Publication Date: March 1, 2007
Citation: Fritschi, F.B., Ray, J.D. 2007. Soybean Lear N, Chlorophyll Content, and Chlorophyll A/B Ratio. Photosynthetica. 45(1):92-98, 2007 Interpretive Summary: Nitrogen concentration in soybean leaf tissue may be a tool for screening soybean lines for increased yield potential; however, measuring nitrogen concentration can be expensive and time consuming. Other researchers have suggested chlorophyll measurements as a substitute for directly measuring nitrogen concentration. The objective of this study was to assess variation in soybean chlorophyll characteristics and to test if chlorophyll concentration and/or composition could be used as a rapid screening method to predict genotypic variation in leaf tissue nitrogen concentration. Over 800 different soybean lines from the USDA-ARS Soybean Germplasm Collection were analyzed. The relationship between leaf chlorophyll and nitrogen concentrations was not sufficiently close for chlorophyll to be useful as a predictive tool for leaf nitrogen concentration against a broad spectrum of soybean genotypes. This research demonstrates that scientists need to either measure nitrogen concentration directly or develop alternatives that do not involve measuring chlorophyll.
Technical Abstract: The objective of this study was to assess genotypic variation in soybean chlorophyll concentration and composition, and to test if these data could be used as a rapid screening method to predict genotypic variation in leaf tissue N concentration. Chlorophyll concentration and composition were examined among 833 soybean (Glycine max L. Merr.) accessions and related to SPAD meter readings and leaf N concentration. In the initial year of the study (2002), the relationship between leaf chlorophyll and leaf N concentration (R2 = 0.043) was not sufficiently close for chlorophyll to be useful as a predictive tool for leaf N concentration. Therefore, leaf N concentration was not determined in 2004 but, samples were again collected for determination of chlorophyll concentration and composition. In 2002, the soybean accessions separated into two distinct groups according to leaf chl a/b ratios, with the majority falling into a group with a mean chl a/b ratio of 3.79. However, approximately 7% of the genotypes could be readily assigned to a group with a mean chl a/b ratio of 2.67. Chl a/b analyses in 2004 confirmed the results obtained in 2002 and of 202 genotypes, all but 6 fell into the same group as in 2002.