Genetic Relationships Among Physiological Processes, Phenology, and Grain Yield Offer an Insight Into the Development of New Cultivars in Soybean (Glycine max L. Merr).

Miguel Angel Lopez,Fabiana Freitas Moreira,Katy Martin Rainey

doi:10.3389/fpls.2021.651241

Abstract

Soybean grain yield has steadily increased during the last century because of enhanced cultivars and better agronomic practices. Increases in the total biomass, shorter cultivars, late maturity, and extended seed-filling period are frequently reported as main contributors for better soybean performance. However, there are still processes associated with crop physiology to be improved. From the theoretical standpoint, yield is the product of efficiency of light interception (Ei), radiation use efficiency (RUE), and harvest index (HI). The relative contribution of these three parameters on the final grain yield (GY), their interrelation with other phenological–physiological traits, and their environmental stability have not been well established for soybean. In this study, we determined the additive–genetic relationship among 14 physiological and phenological traits including photosynthesis (A) and intrinsic water use efficiency (iWUE) in a panel of 383 soybean recombinant inbred lines (RILs) through direct (path analyses) and indirect learning methods [least absolute shrinkage and selection operator (LASSO) algorithm]. We evaluated the stability of Ei, RUE, and HI through the slope from the Finley and Wilkinson joint regression and the genetic correlation between traits evaluated in different environments. Results indicate that both supervised and unsupervised methods effectively establish the main relationships underlying changes in Ei, RUE, HI, and GY. Variations in the average growth rate of canopy coverage for the first 40 days after planting (AGR40) explain most of the changes in Ei. RUE is primarily influenced by phenological traits of reproductive length (RL) and seed-filling (SFL) as well as iWUE, light extinction coefficient (K), and A. HI showed a strong relationship with A, AGR40, SFL, and RL. According to the path analysis, an increase in one standard unit of HI promotes changes in 0.5 standard units of GY, while changes in the same standard unit of RUE and Ei produce increases on GY of 0.20 and 0.19 standard units, respectively. RUE, Ei, and HI exhibited better environmental stability than GY, although changes associated with year and location showed a moderate effect in Ei and RUE, respectively. This study brings insight into a group of traits involving A, iWUE, and RL to be prioritized during the breeding process for high-yielding cultivars.

Highlights

Through the combined contribution of breeding, agronomy, and climate change, soybean yield has achieved a dramatic improvement
These 383 recombinant inbred lines (RILs) come from 32 families classified into three main classes according to the type of cross originally made: high yielding (HY), high yielding under drought conditions (HYD), and diverse ancestry (DA)
High positive additive–genetic correlations were identified for efficiency of light interception (Ei) with AGR40 and K, contrasting with a negative correlation found between Ei and R8, SFL, and radiation use efficiency (RUE) (Table 2)

Summary

Introduction

Through the combined contribution of breeding, agronomy, and climate change, soybean yield has achieved a dramatic improvement. Selection for yield was the first target and later complemented with pest resistance, while proprietary breeding programs joined public efforts at the level of currently providing most of the soybean seed required for farmers in North America (Carter et al, 2004; Specht et al, 2014). Augmented total dry matter production has contributed heavily in better yielding regardless of the mixed reports about increased or constant dry matter partition to the seeds (Kumudini et al, 2001; Rowntree et al, 2014; Balboa et al, 2018). Increase in seed weight is not always consistent or, if positive, less than 0.10 g per 100 seeds, suggesting bigger contribution to increased yield from more seeds per plant, or more plant per hectare (Specht and Williams, 1984; Voldeng et al, 1997; Morrison et al, 2000; Wilson et al, 2014)

Methods

Results

Discussion

Conclusion