|Ainsworth, Elizabeth - Lisa|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2014
Publication Date: 4/30/2014
Citation: Koester, R.P., Skoneczka, J.A., Cary, T.R., Diers, B.W., Ainsworth, E.A. 2014. Historical gains in soybean (Glycine max Merr.) seed yield are driven by linear increases in light interception, energy conversion, and partitioning efficiencies. Journal of Experimental Botany. 65(12):3311-3321. Interpretive Summary: Soybean (Glycine max Merr.) is the world’s most widely grown legume crop and provides an important source of protein and oil for food and animal feed. Soybean yields have increased substantially throughout the past century due to improvements in genetics and farming practices. Yet, the plant physiological mechanisms underlying the historical improvements in soybean yield have not been studied. We investigated 24 soybean cultivars released between 1923 and 2007 in side-by-side field trials. Seed yield increased on average by 26.5 kg ha-1 yr-1, and the increase in seed yield was driven by improvements in the ability of the soybean canopy to intercept light, turn the light energy into biomass and partition carbon to seeds. We found that modern soybean varieties are capturing almost as much light as theoretically possible and partitioning more than 55% of the final biomass to seeds. However, there is room for improvement in the efficiency by which modern soybean varieties convert solar energy into biomass. This study provides a better understanding of the physiological basis for past yield gains in soybean and identifies targets for soybean improvement in the future.
Technical Abstract: Soybean (Glycine max Merr.) is the world’s most widely grown leguminous crop and an important source of protein and oil for food and feed. Soybean yields have increased substantially throughout the past century with yield gains widely attributed to genetic advances and improved cultivars, as well as advances in farming technology and practice. Yet, the physiological mechanisms underlying the historical improvements in soybean yield have not been studied rigorously. In this two year experiment, twenty-four soybean cultivars released between 1923 and 2007 were grown in field trials. Physiological improvements in the efficiencies by which soybean canopies intercepted light, converted light energy into biomass, and partitioned biomass into seed were examined. Seed yield increased on average by 26.5 kg ha-1 yr-1, and the increase in seed yield was driven by improvements in all three efficiencies. Although the time to canopy closure did not change in historical soybean cultivars, extended growing seasons and decreased lodging in more modern lines drove improvements in interception efficiency. Greater biomass production per unit of absorbed light resulted in improvements in conversion efficiency. Over 84 years of breeding, soybean seed biomass increased at a rate greater than total above-ground biomass, resulting in an increase in partitioning efficiency. A better understanding of the physiological basis for yield gains helps identify targets for soybean improvement in the future.