Parsimonious root systems and better root distribution can improve biomass production and yield of soybean

Authors: Fallen, Benjamin; NOH, ENOCH - CLEMSON UNIVERSITY; NARARYANAN, SRUTHI - CLEMSON UNIVERSITY; PAYERO, JOSE - CLEMSON UNIVERSITY

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2022
Publication Date: 6/23/2022
Citation: Fallen, B.D., Noh, E., Nararyanan, S., Payero, J. 2022. Parsimonious root systems and better root distribution can improve biomass production and yield of soybean. PLoS ONE. https://doi.org/10.1371/journal.pone.0270109.
DOI: https://doi.org/10.1371/journal.pone.0270109

Interpretive Summary: Soybean is the most important oilseed and one of the most important and affordable protein sources worldwide. Soybean is the second most-planted field crop, and the second most revenue-generating crop in the United States. The United States, Brazil and Argentina are the top producers of soybean in the world and together, they account for >80% of global soybean production. Worldwide, soybean production is threatened by several environmental stresses, of which drought is one of the most devastating. To date, soybean genetic improvement has primarily focused on increasing yield. However, in recent years, root architecture has gained interest as a selection criterion in breeding programs. Recent research has shown that breeding for individual root characteristics related to yield under stress has advantages over direct selection for yield because the underlying individual root characteristics are likely controlled by less genes than that of yield and demonstrate less genotype-by-environment interaction. The objective of this study was to investigate whether root system characteristics are related with aboveground growth and yield of soybean. Aboveground growth and performance was evaluated by measuring biomass production, leaf area index, seed yield, soil water depletion, and water use efficiency. Root production and root system size were characterized based on root count and root length. Our results demonstrated two novel characteristics of soybean root system architecture that improve aboveground growth and yield. The first demonstrated reduced root development, likely to restrict belowground growth and allocate more resources for shoot growth. This characteristic, which can be referred as a parsimonious root phenotype, might be advantageous for soybean improvement in high input production systems that typically exist in the United States. The second exhibited a similar strategy: while maintaining a root system at an intermediate size, roots were selectively distributed at deeper depths (53-70 cm). The beneficial root characteristics identified in this study (parsimonious root development and selective root distribution in deeper depths) will be useful for breeding programs in developing varieties for optimal, drought, and compacted-soil conditions.

Technical Abstract: Enhancing the acquisition of belowground resources has been identified as an opportunity for improving soybean productivity worldwide. Root system architecture is gaining interest as a selection criterion in breeding programs for enhancing soil resource acquisition and developing climate-resilient varieties. Here we are presenting two novel characteristics of soybean root system architecture that improve aboveground growth and yield. Eleven selected soybean genotypes were tested under rain-fed conditions in 2019 and 2020 at two locations in South Carolina, in which one of the locations was characterized by compacted soils. The elite SC breeding line SC07-1518RR, exotic pedigree line N09-12854, and slow wilting line N09-13890 were superior genotypes in terms of biomass production, seed yield, and water use efficiency. Genotypes N09-12854 and N09-13890 demonstrated reduced root development (based on total root count and length), likely to restrict belowground growth and allocate more resources for shoot growth. This characteristic, which can be referred as a parsimonious root phenotype, might be advantageous for soybean improvement in high-input production systems (characterized by adequate fertilizer application and soil fertility) that exist in many parts of the world. Genotype SC07-1518RR exhibited a similar strategy: while it maintained its root system at an intermediate size through reduced levels of total root count and length, it selectively distributed more roots at deeper depths (53-70 cm). The increased root distribution of SC07-1518RR at deeper depths in compacted soil indicates its root penetrability and suitability for clayey soils with high penetration resistance. The beneficial root phenotypes identified in this study (parsimonious root development and selective root distribution in deeper depths) and the genotypes that possessed those phenotypes (SC07-1518RR, N09-12854, and N09-13890) will be useful for breeding programs in developing varieties for optimal, drought, and compacted-soil conditions.