Skip to main content
ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #62883
Title: INHERITANCE OF ROOT TYPES IN ALFALFA

Author
item JOHNSON, L - CAL/WEST SEEDS
item MARQUEZ-ORTIZ, J - INIFAP-CELALA, APDO
item BARNES, DONALD - RETIRED ARS EMPLOYEE
item Lamb, Joann

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Root characteristics determine how well plants can absorb water and nutrients from soil. We are developing new types of alfalfa that will remove excess nitrate-nitrogen to prevent potential pollution of surface and ground water. To develop new alfalfas with unique root traits, we needed to discover which traits were inherited and which were not under genetic control. Inherited traits are more predictable and can be expressed in different environments. Alfalfa usually has a single deep taproot but has different amounts and sizes of root branches and variable amounts of tiny fibrous roots. Until now, plant breeders have concentrated on developing alfalfa for herbage yield and quality or disease resistance, and roots generally have been ignored. In this research, we studied the heritability and effects of environment of several root traits in alfalfa. We found that taproot width, fibrous root mass, and branch root number, width, and position were heritable. Other root traits studied were not under genetic control and were artifacts caused by the environment. Alfalfa produced larger roots at one location than at another, but relative differences between plant populations with different root types did not change. This means that plant breeders would not be limited to certain locations to study root traits. Larger and more numerous roots were produced when plants had more space to grow, which means that plant breeders must choose consistent spacing to study root traits. These results show that plant breeders should be successful in developing alfalfa with particular root traits, such as strong taproots or many branched roots. These new alfalfas will provide a new tool to protect the environment while providing a valuable crop for farmers.

Technical Abstract: Understanding the inheritance of root traits is essential to determine selection procedures for developing alfalfa (Medicago sativa L.) populations with specifically adapted root types. Objectives of this research were to determine the inheritance of seven root morphological traits of alfalfa, to determine the effect of plant spacing and geographic location on these traits, and to evaluate the association between root traits and fall dormancy and herbage yield. Progenies of diallels with fixed effects, and design II matings with random effects, were planted at two locations in 30 cm rows with 2.5 cm between plants within the row. Plants were evaluated for fall dormancy and herbage yield in late October, 1991, and then dug and evaluated for taproot diameter, lateral root number, lateral root diameter, lateral root position, fibrous root mass, percent determinate taproots, and determinate taproot position. Single plants from mthe ends of the plots were evaluated separately from plants in the middle of the plots. General combining ability was important for taproot diameter, lateral root number, lateral root diameter, lateral root position, and fibrous root mass. These traits had moderate to high heritabilities. No genetic variances were detected for percent determinate taproots or determinate taproot position. Plant spacing affected root morphology, but few progeny X spacing-within-plot effects were observed. Location affected root morphology, but few progeny X location effects were observed. Taproot diameter was the root trait most highly correlated with fall dormancy and herbage yield. Selection for taproot diameter, lateral root number, lateral root diameter, lateral root position, and fibrous root mass at one location with consistent plant spacing should be successful.