Oxygen, Carbon and Nitrogen Isotopes Composition of Cultivated and Wild Soybean.

Biological and physical processes influence the isotopic composition of plants. Carbon and O isotope discrimination can be used in efforts to select and breed for crop cultivars with greater drought tolerance while N isotope signatures is widely used to assess biological N fixation. However, efforts leveraging O, C and/or N isotope signatures have not been extensively researched in cultivated (Glycine max) or wild (G. soja) soybean.

To characterize and compare isotope signatures in cultivated and wild soybean, diversity panels of 83 cultivated soybean plant introductions (PIs) and 83 wild soybean genotypes were grown in field experiments in 2013 and 2014. Shoot tissue isotope analyses from the 2013 season revealed δ¹⁸O, δ¹³C and δ¹⁵N values of cultivated soybean ranging from 20.1 to 23.6‰, -32.7 to -26.7‰, and 1.6 to 5.9‰, respectively, and averages of 22.1 (δ¹⁸O), -28.6 (δ¹³C), and 4.1 ‰ (δ¹⁵N). The ranges of isotope signatures for the wild genotypes were 21.3 to 26.0‰ (δ¹⁸O), -32.5 to -26.3‰ (δ¹³C), and 2.7 to 9.1‰ (δ¹⁵N), with averages of 23.5 (δ¹⁸O), -27.6 (δ¹³C) and 6.3‰ (δ¹⁵N). While two populations had similar ranges of δ¹³C signature, overlapping set broader ranges in δ¹⁸O and δ¹⁵N were observed in wild compared to cultivated soybean. Thus, preliminary results suggest that wild soybean genotypes may encompass diversity in δ¹⁸O and δ¹⁵N signatures that may be useful for soybean breeders.