Is there potential to adapt soybean (Glycine max Merr.) to future [CO₂]? An analysis of the yield response of 18 genotypes in free‐air CO₂ enrichment

Abstract

Rising atmospheric [CO2] is a uniform, global change that increases C3 photosynthesis and could offset some of the negative effects of global climate change on crop yields. Genetic variation in yield responsiveness to rising [CO2] would provide an opportunity to breed more responsive crop genotypes. A multi-year study of 18 soybean (Glycine max Merr.) genotypes was carried out to identify variation in responsiveness to season-long elevated [CO2] (550 ppm) under fully open-air replicated field conditions. On average across 18 genotypes, elevated [CO2] stimulated total above-ground biomass by 22%, but seed yield by only 9%, in part because most genotypes showed a reduction in partitioning of energy to seeds. Over four years of study, there was consistency from year to year in the genotypes that were most and least responsive to elevated [CO2], suggesting heritability of CO2 response. Further analysis of six genotypes did not reveal a photosynthetic basis for the variation in yield response. Although partitioning to seed was decreased, cultivars with the highest partitioning coefficient in current [CO2 ] also had the highest partitioning coefficient in elevated [CO2]. The results show the existence of genetic variation in soybean response to elevated [CO2], which is needed to breed soybean to the future atmospheric environment.

Phenotypic plasticity conditions the response of soybean seed yield to elevated atmospheric CO2 concentration

“…Since no significant CO 2 3 cultivar interaction in the efficiency in pod production among the cultivars was observed in this study (Supplemental Table S1), the cultivars with the strongest responsiveness of biomass to eCO 2 produced more pods and a greater seed yield, in agreement with Bishop et al (2015), who compared 18 cultivars over two seasons in a free-air carbon dioxide enrichment study. It is interesting that, although we observed a difference in the photosynthetic stimulation due to eCO 2 among the nine cultivars, the degree of photosynthetic stimulation was not related to that of seed yield (Table I), which is in agreement with the previous findings (Ziska et al, 2001;Shimono et al, 2009;Bishop et al, 2015). Thus, there was no evidence for the contribution of leaf photosynthesis and NSC accumulation Table I.…”

“…The present study confirms that the methodology of Shimono (2011) can be used in prescreening to select eCO 2 -responsive soybean cultivars. Some researchers have expressed concerns about the heritability of the CO 2 response in soybean (Bishop et al, 2015) and in other crops. Our experiment raised the possibility that CO 2 responsiveness is heritable, since the most responsive cultivar (cv Mandarin) is a parent of the second most responsive cultivar (cv Harosoy).…”

“…Kimball et al, 2002), since [CO 2 ] is a growth-limiting resource for C 3 plants. There is a large genotypic variation in the yield response to eCO 2 , both among cultivars and between species, with responses ranging from -15% to +20% per 100 mmol mol -1 CO 2 increase from the current level for rice (Ziska et al, 1996;Moya et al, 1998;Baker, 2004;Shimono et al, 2009;Hasegawa et al, 2013), -6% to +35% for wheat (Manderscheid and Weigel, 1997;Ziska et al, 2004;Ziska, 2008;Tausz-Posch et al, 2015), -5% to +55% for soybean (Ziska and Bunce, 2000;Ziska et al, 2001;Bishop et al, 2015;Bunce, 2015), and -6% to +21% for field bean (Phaseolus vulgaris; Bunce, 2008). These large differences in eCO 2 responsiveness within crop species suggest that active selection and breeding for genotypes that respond strongly to gradual but steadily increasing [CO 2 ] may ensure sustained productivity and improve food security in a future eCO 2 world (Ainsworth et al, 2008;Ziska et al, 2012;Tausz et al, 2013).…”

Using FACE Systems to Screen Wheat Cultivars for Yield Increases at Elevated CO2

“…Intraspecific variation in the responsiveness of yield has been reported in many C 3 crops species: barley [1], common bean [2], cow pea [3], oat [4], rape [5], rice [6,7], soybean [8,9], and wheat [10,11]. Such variation could allow the achievement of larger field yield increases as CO 2 rises, if new cultivars could be developed to better exploit the rising CO 2 [12].…”

“…The two FACE experiments which have compared the largest number of cultivars have been for up to 18 cultivars of soybeans in Illinois [8] and eight cultivars of rice in Japan [6]. The FACE rings were 20 m in diameter for soybean (but only one-half of the plot was used for the 18 cultivars), and 17 m diameter for rice.…”