Evaluating Soybean Germplasm for Specific Leaf Weight

Abstract

Specific leaf weight (SLW) defined as the mass of tissue per unit leaf area has been positively correlated with leaf photosynthesis in several species and has therefore been suggested as a potentially useful selection criterion. Little research has been done to assess the range in genetic variability of SLW in soybean [Glycine max (L.) Merr.] as a first step in evaluating the potential of selection for SLW. In previous reports, comparisons of SLW among lines of differing maturity have been confounded with environmental conditions associated with the various sampling times. The objectives of this research were to determine the phenotypic variability of SLW that exists in a portion of the Maturity Group I soybean germplasm of comparable maturity, and to estimate the genetic component of that variability. Four leaf discs, 8.7 mm in diam., were cut from each of two leaflets of five plants for 231 Maturity Group I accessions in the USDA soybean germplasm collection. One leaflet each was collected from the most recently fully expanded leaf and the next youngest leaf on each plant between R5 and R6 growth stages. All selected leaves were in an unshaded position in the canopy and sampled near solar noon on clear sky days. Plots were grown at Urbana, IL in 1983 and 1984 and at West Lafayette, IN in 1984 with one replication in each environment. Averaged across all locations and years accession means for SLW ranged from 47 to 86 g m−2. ‘Hodgson 78’ replicated nine times in each 1984 environment, had a mean SLW of 62 g m−2. Repeatability for SLW was 0.48 indicating that effective selection for this trait should be possible.