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USDA-ARS, Forage and Range Research Lab., 695 N. 1100 E., Logan, UT 84321-6300
Logan, UT. Joint contribution of the Utah Agricultural Experiment Station, Utah State University and the USDA-ARS
* Corresponding author (Mike.Peel{at}ars.usda.gov).
ABSTRACT
‘Don’ (Reg. No. CV-205, PI 655519), a diploid falcata alfalfa (Medicago sativa subsp falcata L.), was developed by the Forage and Range Research Laboratory in Logan, UT, in cooperation with the Utah Agricultural Experiment Station, Utah State University. Recent interest in falcata alfalfa has been high due to its value for increasing the productivity of rangelands. Don was selected for persistence under harsh conditions, uniform yellow flower color, increased seed production, and large-stature plants. Don traces to PI20725, an original collection made by N.E. Hansen in the Don Province of Russia. Don was tested as AU021. Don is significantly more persistent than typical sativa (M. sativa Subsp sativa L.)–type alfalfas and is meant for use in mixed plantings with grasses either in range or pasture situations typical of the Intermountain region of the western United States. In comparative trials, including irrigated and nonirrigated, where 25 to 50% mortality was observed on sativa alfalfas, Don showed no mortality. When used in mixtures, the production advantage of Don with tall fescue [Schedonorus phoenix (Scop.) Holub; syn. Festuca arundinaceae Schreb.] and meadow brome (Bromus riparius Rehm.) ranged from 10 to 32% When Don is grown with crested wheatgrass on dry rangelands, similar production advantages are expected, which will make rangelands more productive. Furthermore, when grown in mixtures with grasses, Don will not dominate; rather, it has a low growth habit and stays well below the canopy of most cool-season grasses.
The usefulness of falcata-type alfalfa in rangelands has been mentioned in both the popular press and in the scientific literature. Hendrickson et al. (2007), Mortenson et al. (2005), and Xu et al. (2004) demonstrated the value of including a falcata-type alfalfa in rangeland situations to increase long-term productivity. Mortenson et al. (2005) in particular stated that "the practice of interseeding yellow flowered alfalfa into rangelands is sustainable over decades and will increase forage production and improved nutritive value." The value of the falcata-type alfalfas are also being recognized by producers, and it is being referenced in farm and trade magazines (Bliss, 2003; Peck, 2008; Smith 1996). Much of the activity can be traced to Smith (1996), who described naturalized falcata alfalfa on his ranch in South Dakota. Smith indicated that the falcata alfalfa on his ranch likely originated from seed sent by N.E. Hansen of South Dakota State University to his great uncle (Charlie Smith) in 1915. Hansen's practice of sending samples of alfalfa seed to ranchers and producers was well documented by Rumbaugh (1979), corroborating Smiths origin for the falcata alfalfa he uses.
‘Don’ (Reg. No. CV-205, PI 655519) is a diploid falcata alfalfa (Medicago sativa subsp. falcata L.) developed by the USDA–ARS Forage and Range Research Laboratory and the Utah State University Agriculture Experiment Station (Logan, UT). Don was tested under the experimental designation AU021. It was publicly released on 31 Jan. 2008. Don represents a new approach in alfalfa development; is being released for use exclusively in mixed plantings and is meant for use on semiarid rangelands and irrigated pastures. It is being released because of its high persistence under harsh conditions and when grown in a mixture with grasses. In addition, because of its low growth, it does not dominate in a mixed planting. Don should prove useful to private and public land mangers for use on Conservation Reserve Program–type plantings and in revegetation of degraded rangelands and improved pastures. It should be of particular interest to public land managers interested in a persistent, nonaggressive legume.
The name Don was chosen as a reflection of its origin. Its history is rather exceptional and is provided verbatim as recorded in available records. A population of Don alfalfa was obtained by Dr. M.W. Adams of South Dakota State University from the University of British Columbia about 1950. This population was derived from the original PI 20725 collected by N.E. Hansen in the Don Province of the Lower Volga region of Southeast Russia. Rumbaugh (1979) listed one of Hansen's collections as S.P.I. 20725 and described the contribution of S.P.I. 20725, which is probably PI 20725.
Methods
In the early 1960s, PI 20725 was used by Dr. Melvin D. Rumbaugh in genetic studies at Brookings, SD. The studies included seven other diploid alfalfas, which are minimally described in Tamimi and Rumbaugh (1963). After a number of years, Rumbaugh noted that remnants from PI 20725 were persisting in some subsequent tetraploid alfalfa breeding nurseries. Seed collected from these surviving plants (the exact number was not recorded) was used to establish the original breeding nursery. While the collected material was uniformly expressing the Don phenotype, it is certainly possible that crossing occurred with other diploid alfalfa in the original studies. The original breeding nursery was evaluated at Brookings, SD, where one cycle of selection was completed in 1976 for uniform flower color and increased plant size and seed production. A second evaluation nursery was established in 1978, and a cycle of selection was completed at the Utah State University's Agriculture Experimental Station Bluecreek Farm. The Bluecreek Farm receives an annual precipitation of 36.5 cm, mostly in the form of snow during the winter months. A third cycle of selection was initiated in 1984 at Utah State University's Evans Farm (Providence, UT), which receives an average annual precipitation of 44.0 cm. Selection focused on persistence, yellow flower color, and increased plant size and seed production. In 1997, a 1500-plant nursery was established at Evans Farm. The material was evaluated in 1998 and 1999, and 96 plants were selected in fall 1999. Large-stature upright plants of uniform fine-leaf type and yellow flower color were selected. Seed from these plants was produced in isolation and designated Breeder seed. This seed was used to establish a foundation seed field in Logan, UT, in 2002.
Data Collection
Don was tested as AU021 in six separate trials to measure establishment, persistence, forage yield, and production when grown in mixtures with tall fescue [Schedonorus phoenix (Scop.) Holub; syn. Festuca arundinaceae Schreb.] and meadow brome (Bromus riparius Rehm.). Trials were on Utah State University experimental farms at Nephi, UT (annual precipitation 30 cm), Evans Farm, and Bluecreek. In 2002, a trial was established at Evans Farm to test Don in monocultures with other alfalfas and in mixtures with ‘Martin’ tall fescue and ‘Cache’ meadow brome. The trial was established as a randomized complete block design (RCBD) with a strip plot arrangement using the line-source irrigation system described by Hanks et al. (1976). Reported data are only from the highest irrigation level meeting evapotranspiration and the lowest not receiving any supplemental irrigation. Mortality was estimated from the mixed seeding with grasses following Vogel and Masters (2001). This consisted of the number of squares (15 cm2) out of 32 containing a live plant and reported as a percentage. In 2003, dryland trials were established in an RCBD at Nephi and Bluecreek with the primary purpose to compare the relative persistence of Don with other commonly available cultivars and secondarily to compare relative forage production under harsh conditions. A relative dormancy was determined following a modified version of the method of Teuber et al. (1998) at Nephi, the difference being that irrigation was not possible. However, in 2005 sufficient fall rainfall occurred at the Nephi location to initiate growth. Mortality in these trials was the difference between actual plant counts from the original and final plant populations. A second dryland uniform trial was established in an RCBD at Evans Farm and Bluecreek in 2004 to measure establishment and forage yield. In 2005, a trial was established in an RCBD at Evans Farm with other falcata and sativa alfalfas. All forage harvests were with a Swift Current Sickle bar harvester (Swift Current, SK).
A Partec PA II flow cytometer (Münster, Germany) was used to verify Don's ploidy level using Partec's CyStain UV Precise P kit and protocol. A plant of ‘Vernal’ alfalfa (Brink et al., 1955) known to be a tetraploid was used as a standard, and 120 seedlings of Don were tested. The seedlings were then grown out to characterize the morphology of Don.
Characteristics
Long-term persistence is difficult to demonstrate without trials that extend for the duration of expected persistence. Even so, we were able to demonstrate Don's potential for persistence. Don showed no decrease in plant stand over a 3-yr period when grown in a monoculture or mixtures with tall fescue or meadow brome (Table 1 ). In the same trial, no differences in mortality among alfalfa cultivars were observed when grown in monocultures with irrigation; however, without irrigation, Amerigraze and P53V08 showed significantly more mortality than Don. Furthermore, when grown in mixtures with grasses, ‘Ladak’, ‘Spreador3’, ‘Amerigaze’, and ‘P53V08’ showed significant mortality, ranging from 25 to nearly 50% In contrast, Don showed no measurable mortality when grown in mixtures with either meadow brome or tall fescue (Table 1). Variable results for mortality were observed under dryland conditions. No significant differences among entries were observed at Bluecreek for mortality (Table 2 ). However, mortality was high among most cultivars at Nephi, with Don showing significantly less mortality than three of the four check cultivars used for comparison.
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It was apparent from all trials that Don is highly dormant. In fall 2005 conditions at Nephi were favorable to collect dormancy data. Average ratings were 1.0, 4.8, 2.6, 3.5, and 2.2 for Don, ‘Dona Ana’, Ladak, Saranac, and Vernal, respectively. Initiation of vigorous spring growth can be as much as a week behind Vernal, and after the initial spring growth Don will go completely dormant without moisture. When dry conditions persist during autumn, plants of Don may appear to have died when they are actually only dormant and will regrow the following spring.
Histograms from the flow cytometery showed Don with peaks at one-half the gain of Vernal, a teraploid (2n = 4x = 32), demonstrating that Don is a diploid. Based on the number of plants tested, if teraploid plants were present in the cultivar, they would represent less than 1% of individuals.
Morphological Characteristics
Don has a semidecumbent bowl-shaped growth habit like that describe by Sinskaya (1950) as a 2 to 3. The low growth habit will not be a detriment to grazing but does make it difficult to harvest with a mechanical harvester. This is a probable reason that its yield is lower in trials where much of the forage is not picked up by a mechanical harvester. When used as intended for grazing in mixtures with grasses, the low growth habit of Don could be an advantage. Its growth does not extend above the canopy of most grasses, whereas growth of typical sativa-type alfalfa can extend above the canopies of many grasses.
Don has yellow flowers. During Foundation seed production, plants with light purple and variegated flowers were observed. These accounted for less than 1% of the plants and were rogued out. During the late bud stage, 1 to 2% of the flower buds were observed to have a purple hue, but after these flowers were fully opened they were indistinguishable from any other yellow flower. The bright yellow flowers of Don are attractive and as such should make it desirable for use as a low-maintenance ornamental along roadways in the Intermountain western United States. After maturity, the mature seeds would provide a source of protein to wildlife throughout winter months. Under favorable conditions, Don flowers later than Vernal and tends to be somewhat later maturing. Pod shape ranges from sickle to one complete coil. Don has small fine leaves and fine stems. Seeds of Don are small, with 880,000 seeds kg–1, compared to typical commercial alfalfa around 500,000 seeds kg–1. Those unfamiliar with the seed of Don could easily confuse it with seed of sweet clover [Melilotus officinalis (L.) Pallas]. It also has a high percentage of hard seed, which has been measured from 50 to as high as 78%. For range seeding situations, this should prove to be an advantage when dormant seeding Don with grasses during autumn as germination of the hard seed would be delayed. Because of its small seed size, it is not necessary to plant more than 1 kg ha–1 for mixed seedings. Planting for seed production should be much less.
The rooting characteristics of Don are much different than a typical sativa-type alfalfa. Rooting depth is much less, and the roots are more fibrous. The crown of Don is typically 3 to 4 cm below the soil surface, with some buds much lower. While not quantified, it has been observed that the top main part of the crown can be removed, and the plants will still initiate growth from well below the soil surface.
Availability
Breeder and Foundation seed will be maintained by the USDA–ARS Forage and Range Research Laboratory, Logan, UT. Seed will be made available to commercial growers by the Utah Crop Improvement Association, Logan, UT 84322-4820 for production of Registered and Certified seed. Breeder and Foundation seed have been produced by the Forage and Range Research Laboratory. Small seed samples for research purposes can be obtained from the National Plant Germplasm System. Appropriate recognition should be given when this cultivar contributes to the development of new germplasm or cultivars.
Footnotes
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication October 13, 2008.
References
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