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Title:   Author  item
                                            KOESTER, R - University Of Illinoisitem
                                            Skoneczka, Jeffreyitem
                                            DIERS, B - University Of Illinoisitem
                                            Ainsworth, Elizabeth

                                                         - *Lisa*
  Submitted to: Plant Biology Annual Meeting
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 5/1/2012
                                    Publication  Date: 7/20/2012
                                    Citation: Koester, R.P., Skoneczka, J.A., Diers, B.W., Ainsworth, E.A. 2012. Identifying physiological gains in the historic Midwest soybean germplasm [abstract]. Plant Biology Annual Meeting. Paper No. P29001.Interpretive Summary:
                                Technical Abstract: Soybean yields in the US have steadily increased throughout the past century due to advances made in breeding and management practices. Despite these historical gains, world food production must increase by 50% by 2030 to meet population demands according to the UN, raising the question of whether the current rate of yield increase will meet this demand. Although there is a directed effort to increase yield potential through targeted biotechnological strategies, there is a knowledge gap on how traditional breeding has physiologically altered plants to achieve current soybean yields. In order to identify physiological changes that have contributed to yield improvement, 24 soybean cultivars with release dates spanning 1923 to 2007 were grown in Champaign, IL. Physiological traits including photosynthetic rate, maximum Rubisco activity, maximum electron transport rate, dark respiration rate, and efficiencies of light interception (Ei), solar energy conversion (Ec), and carbon partitioning (Ep) were measured. Over the 84 years of genetic improvement examined, daily photosynthetic carbon uptake was shown to have a significant positive linear trend which amounted to a 7.7% total gain at mid vegetative growth and an 11.8% total gain at early reproductive development, but not at later stages when drought stress was severe. Season-long averages of Ei and Ec did not change with year of release, while Ep increased linearly by a 21.9% total gain during the years examined. Yield increased by 16.7 kg/ha per year for a total increase of 72.3%. While Ei and Ep are thought to be theoretically at maxima, Ec is below the theoretical maximum and therefore has been suggested as a target for improvement. Further understanding of what physiological traits have been altered in the historic soybean germplasm could lead to targeted strategies for future increases in soybean yield potential.


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