Physiological processes associated with soybean genetic progress in Argentina

Abstract

The main physiological processes associated with soybean [Glycine max (L.) Merr.] genetic yield progress in central temperate Argentina are largely unknown. This knowledge is critical to identify opportunities to accelerate yield gains via trait‐based hybridization. Our objectives were to: (a) evaluate the influence of biomass accumulation vs. harvest index (HI) in explaining genetic progress, and (b) assess the role of radiation and/or N capture and use efficiency (RUE and NUE, respectively) as drivers of biomass accumulation. We tested 173 cultivars released from 1980 to 2014 in two high‐yielding environments. Additionally, a crop modeling exercise was performed to demonstrate the physiological perception that any genetic increase in RUE would only translate into more yield if there is enough water for the realization of that RUE. Observed genetic progress was 42 kg ha−1 yr−1, or ∼1% yr−1, and was mostly explained by increased aboveground biomass accumulation. This higher biomass of modern cultivars was associated with increased RUE and total N uptake. This suggests that, if residual genetic variation is still present in current soybean cultivars, future genetic improvements should focus on further improving N uptake to increase RUE. Increases in RUE are associated with increased stomatal conductance and water use. Therefore, it would be expected that genetic progress is faster in environments with increased rainfall. Our modeling exercise was consistent with this hypothesis and showed that soybean genetic progress simulated in different locations within a rainfall gradient was positively associated with cumulative seasonal precipitation.

Genetic improvement of soybeans in Brazil: South and Midwest regions

“…(2016) reported a genetic gain of 43 kg ha −1 yr −1 . In a more recent study, the same authors reported similar results, with a genetic gain of 42 kg ha −1 yr −1 or approximately 1% yr −1 (de Felipe et al., 2020); estimated rates of genetic gain higher than those obtained in our study and those reported in the previously mentioned studies performed in other countries. The studies by de Felipe et al.…”

“…Studies performed in other important countries, have reported rates of genetic gain similar to those obtained in this study for the Midwest Region, such as in the United States (approximately 10 to 23 kg ha −1 yr −1 ), China (approximately 6 to 16 kg ha −1 yr −1 ), India (approximately 23 kg ha −1 yr −1 ), and Canada (approximately 10 kg ha −1 yr −1 ), but lower than those obtained in recent studies (approximately 43 kg ha −1 yr −1 ) conducted in Argentina (Boehm Jr. et al., 2019; de Felipe et al., 2016, 2020; Jin et al., 2010; Morrison et al., 2000; Ramteke et al., 2011; Rincker et al., 2014; Rogers et al., 2015; Wang et al., 2016; Wu et al., 2015). However, as previously discussed, the rates of genetic gain are highly dependent on the set of genotypes tested and the number of environments evaluated, which may explain the differences observed in the cited studies.…”

“…The studies by de Felipe et al. (2016, 2020) evaluated crops in only three and two environments (location × year), respectively. In contrast, the present study and most of the previously mentioned studies involved several environments and a wide cultivation area, where the average yield of the cultivars tended to be lower.…”

“…In the recent studies, de Felipe et al. (2016, 2020) evaluated soybean genetic gain arising from conventional (nontransgenic), RR1, and RR2 IPRO technologies from 1980 to 2015 in Argentina. These authors did not observe discontinuities in rates of genetic gain across the years, suggesting that there were no qualitative yield advantages associated with the biotechnological events, although the importance of these technologies for the management of the crop is incontestable.…”

“…In a more recent study, the same authors reported similar results, with a genetic gain of 42 kg ha −1 yr −1 or approximately 1% yr −1 (de Felipe et al, 2020); estimated rates of genetic gain higher than those obtained in our study and those reported in the previously mentioned studies performed in other countries. The studies by de Felipe et al (2016de Felipe et al ( , 2020) evaluated crops in only three and two environments (location × year), respectively. In contrast, the present study and most of the previously mentioned studies involved several environments and a wide cultivation area, where the average yield of the cultivars tended to be lower.…”