Phenotyping seedlings for selection of root system architecture in alfalfa (Medicago sativa L.)

Plant Methods

Bruna Bucciarelli¹  Samadangla Ao²  Yuanyuan Cao³  Christopher N. Topp⁴  Maria J. Monteros⁵  Zhanyou Xu⁶  Deborah A. Samac⁷ 

[1] Department of Agronomy and Plant Genetics, University of Minnesota, 1991 Upper Buford Circle, 55108, St. Paul, MN, USA;Department of Agronomy and Plant Genetics, University of Minnesota, 1991 Upper Buford Circle, 55108, St. Paul, MN, USA;Kohima Science College, 797002, Jotsoma, Nagaland, India;Department of Plant Pathology, University of Minnesota, 1991 Upper Buford Circle, 495 Borlaug Hall, 55108, St. Paul, MN, USA;School of Life Sciences, Anhui Agricultural University, 230036, Hefei, Anhui, China;Donald Danforth Plant Science Center, 975 N Warson Road, 63132, Olivette, MO, USA;Noble Research Institute, 2510 Sam Noble Parkway, 73401, Ardmore, OK, USA;Bayer Crop Science, 63017, Chesterfield, MO, USA;USDA-ARS, Plant Science Research Unit, 1991 Upper Buford Circle, 55108, St. Paul, MN, USA;USDA-ARS, Plant Science Research Unit, 1991 Upper Buford Circle, 55108, St. Paul, MN, USA;Department of Plant Pathology, University of Minnesota, 1991 Upper Buford Circle, 495 Borlaug Hall, 55108, St. Paul, MN, USA;

关键词: Alfalfa;    Branch root;    Root system architecture;    Seedling phenotyping;    Tap root;   

DOI  :  10.1186/s13007-021-00825-3

来源: Springer

【 摘 要 】

BackgroundThe root system architecture (RSA) of alfalfa (Medicago sativa L.) affects biomass production by influencing water and nutrient uptake, including nitrogen fixation. Further, roots are important for storing carbohydrates that are needed for regrowth in spring and after each harvest. Previous selection for a greater number of branched and fibrous roots significantly increased alfalfa biomass yield. However, phenotyping root systems of mature alfalfa plant is labor-intensive, time-consuming, and subject to environmental variability and human error. High-throughput and detailed phenotyping methods are needed to accelerate the development of alfalfa germplasm with distinct RSAs adapted to specific environmental conditions and for enhancing productivity in elite germplasm. In this study methods were developed for phenotyping 14-day-old alfalfa seedlings to identify measurable root traits that are highly heritable and can differentiate plants with either a branched or a tap rooted phenotype. Plants were grown in a soil-free mixture under controlled conditions, then the root systems were imaged with a flatbed scanner and measured using WinRhizo software.ResultsThe branched root plants had a significantly greater number of tertiary roots and significantly longer tertiary roots relative to the tap rooted plants. Additionally, the branch rooted population had significantly more secondary roots > 2.5 cm relative to the tap rooted population. These two parameters distinguishing phenotypes were confirmed using two machine learning algorithms, Random Forest and Gradient Boosting Machines. Plants selected as seedlings for the branch rooted or tap rooted phenotypes were used in crossing blocks that resulted in a genetic gain of 10%, consistent with the previous selection strategy that utilized manual root scoring to phenotype 22-week-old-plants. Heritability analysis of various root architecture parameters from selected seedlings showed tertiary root length and number are highly heritable with values of 0.74 and 0.79, respectively.ConclusionsThe results show that seedling root phenotyping is a reliable tool that can be used for alfalfa germplasm selection and breeding. Phenotypic selection of RSA in seedlings reduced time for selection by 20 weeks, significantly accelerating the breeding cycle.

【 授权许可】

CC BY