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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #93255
Title: A METHOD TO CHARACTERIZE ROOT MORPHOLOGY TRAITS IN ALFALFA

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

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Forage yield and long term survival of plants is believed to be influenced by root growth patterns in alfalfa. Historically, root research has been conducted under field environments with plants being dug for evaluation over several years. Studying field grown root systems is labor intensive and time consuming. Therefore, the idea of using greenhouse and modified field environments to study root traits in alfalfa would be attractive. Results showed that greenhouse environments or transplanting plants from the greenhouse to the field were not appropriate for studying root traits in alfalfa. Characterization of alfalfa root traits should be conducted at the end of the first growing season in seeded plots in the field with uniform spacing between plants. This research describes a useful method for characterizing root traits that can be used in plant breeding programs to develop new varieties with increased forage yield and long term survival lof alfalfa.

Technical Abstract: Productivity and persistence in alfalfa (Medicago sativa L.) has been shown to be influenced by root morphology. Our objectives were to identify the optimum age, cultural practices, and environmental conditions to characterize taproot diameter (TD), lateral root number (LRN), fibrous root mass (FRM), and determinate taproot percentage (DTP) in alfalfa. Experiments were conducted with diverse alfalfa germplasms to study (1) root trait development over time during the establishment year; (2) the relationship of root traits evaluated under greenhouse vs. field conditions; (3) the effect of seeding vs. transplanting and plant spacing; (4) the effect of different locations, N fertilizer, and years on root morphology traits. No germplasm differences were observed for rate of root trait development and both solid seeded and spaced plants reached a plateau in rate at approximately 17 weeks of age. No correlations were found between greenhouse cultured plants and 21 week old field grown plants for LRN or FRM. Transplanting alfalfa caused most plants to have a branched taproot at the point where the tip of the taproot had been at the time of transplanting (determinate taproot). All root traits were affected by plant spacing, but no germplasm by plant spacing interactions were found. Only TD had a significant germplasm by location interaction. Both TD and LRN increased with N fertilizer and between the establishment and first production years, but no germplasm by N rate or germplasm by year interactions were found. Characterization of LRN and FRM in alfalfa should be conducted in seeded field plots with uniform plant spacing at one location 22 weeks after planting. More than one location would be desirable for characterization of TD.