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a USDA-ARS and North Carolina ARS, 1119 Williams Hall, Raleigh, NC 27695-7620
b BASF Plant Science, 26 Davis Dr., Research Triangle Park, NC 27709
c 13 Furches St., Raleigh, NC 27695
* Corresponding author (joe_burns{at}ncsu.edu).
‘Performer’ switchgrass [Panicum virgatum L.] (Reg. No. CV-247, PI 644818) was cooperatively developed as a cultivar by the USDA-Agricultural Research Service and the North Carolina Agricultural Research Service, North Carolina State University, Raleigh, NC and released on 1 November 2006. Incorporation and preservation of the unique switchgrass germplasm adapted to the Southeastern U.S. is important in the development of a new cultivar with improved nutritive value and, hence, forage quality (i.e., intake and digestion). Generally, forage quality and dry matter yield are negatively associated. The development of this new cultivar retained acceptable dry matter yield, but with improved nutritive value over existing cultivars, and over other adapted warm-season grasses, which is valuable to the ruminant industry.
Performer was developed from three cycles of selection occurring under natural environmental conditions. The original source population (Cycle 0) consisted of a selected group of 161 lowland form switchgrass plants, representing 11 different germplasm sources. The 11 germplasm sources, with cultivar or location of origin in parentheses, were 63–85 (Pangburn), 63–90 (Kanlow), 63–78 (SC 56–23), 63–69 (Pinehurst, NC), 63–79 (Wilmington, NC), 63–75 (Bn-11361), 63–73 (F-687, Am-181, Stuart), 63–76 (Bn-11362), 63–72 (F-286, Am-180, Wahass, O.), 63–70 (Pinehurst, NC), and 63–71 (Am-175, Jasper County, SC). The 161 plants were evaluated for dry matter yield and in vitro dry matter digestion (IVDMD). A total of 31 plants were selected from this group on the basis of the arithmetic product of forage yield and IVDMD. These plants, in addition to two other plants that were selected to maintain their germplasm [accession 63–87 (Pangburn)], were allowed to cross-pollinate at random, with the resulting progeny bulked in equal amounts across clones to represent Cycle 1.
Cycle 1 was represented by the 660 half-sib progeny derived from the 33 selected Cycle 0 plants. The progeny were evaluated for dry matter yield, IVDMD and N concentration (Talbert et al., 1983; Godshalk et al., 1986). A total of 33 plants were selected for various combinations of these traits. Six synthetic populations were formed using three different indices. Index I had weights of one for initial growth yield, zero for IVDMD and zero for N concentration. A value of zero was assigned to N concentration to establish it as a covariate, thus preventing declines in N concentration as a result of selection. One 16-clone synthetic was produced. A second index (Index II), with weights of one on initial growth yield, 62 on IVDMD, and zero for N concentration, produced 16-, 8-, and 4-clone synthetics. The third index (Index III) consisted of weights of zero on initial growth yield, one for IVDMD, and zero for N concentration. One 16-clone synthetic and a 4-clone synthetic were produced from Index III. A given plant (among the 33 plants selected) was frequently present in more than one synthetic. All six synthetics were planted in crossing blocks and allowed to open pollinated in isolation from one another. The progeny were subsequently harvested and bulked in equal amounts across clones to constitute Cycle 2.
Cycle 2 consisted of open-pollinated progeny from the six synthetics described above. As a result of varied representation in the six synthetics of the 33 plants selected from Cycle 1, family size of the progeny ranged from 20 to 100 members per half-sib family. The 33 Cycle 2 families (progeny) were evaluated in a randomized complete block design with four replicates at the Central Crops Research Station at Clayton, NC during 1985 and 1986 (Godshalk et al., 1988a, 1988b). Each progeny row contained seven plants and data were collected on the middle five plants of a given row. Dry matter yield and IVDMD data were recorded for initial growth (June) and regrowth (late July to early August), all in the boot to early emergence stage and on a per plant basis, for each of the progeny rows. The plants were ranked for IVDMD over initial growth and regrowth, and the top eight plants were selected to constitute Cycle 3. The eight selected plants were transplanted into an isolated crossing block, with 16 replicates per plant. They were allowed to open-pollinate and the seed was harvested and bulked evenly by weight to constitute Breeder seed of the cultivar Performer. Seed was harvested from this polycross nursery over two years.
Performer switchgrass was selected for its improved IVDMD, with consideration to digestible nutrients per hectare when grown in replicated experiments, which included the commercial cultivars Alamo and Cave-in-Rock. These cultivars represented a widely used lowland type and an upland type, respectively. Plantings were made in two different climatic and geological regions. Trials were located in the Tide Water Coastal Plain and conducted at the Tidewater Research Station, Plymouth, NC, and in the Central Coastal Plain and conducted at the Central Crops Research Station, Clayton, NC. Experiments were conducted up to four years following the year of establishment. Samples were obtained at harvest in the last two to three years of each experiment, depending on location. Three harvest dates at both locations were during the end of May, end of July, and early October, from late vegetative to early heading growth stages. Samples were oven-dried to a constant weight, ground, and used for subsequent laboratory analysis to estimate IVDMD and other nutritive value constituents.
The IVDMD of Performer (565 g kg–1) was highly significantly (P < 0.01) greater than that of both Cave-in-Rock (523 g kg–1) and Alamo (523 g kg–1), while lignin concentration of Performer (54 g kg–1) was highly significantly (P < 0.01) less than the lignin concentration of both Cave-in-Rock (63 g kg–1) and Alamo (62 g kg–1). Crude protein concentrations were similar among the three cultivars, averaging 72 g kg–1. Although dry matter yield of Performer (12,811 kg ha–1) was less compared to Alamo (14,529 kg ha–1, P = 0.02), it is important to note that the yield of digestible forage (dry matter yield x IVDMD) was not different between Performer (7567 kg ha–1) and Alamo (7984 kg ha–1). This means that the producer sacrifices no losses in the production of digestible dry matter hectare–1 by the use of Performer, which has potential to improve animal daily performance.
Two cultivars and five synthetics were harvested for hay in June and fed to steers surgically modified with an esophageal fistula to permit the collection of the consumed forage representing the animals diet (masticate). Masticates were quick-frozen in liquid nitrogen, freeze dried and passed through a vibrating sieve to determine masticate particle size. The whole masticate (animal diet) showed all entries to be similar in percentage dry matter (137 g kg–1), but differed in median particle size, IVDMD and NDF. Performer had larger median particle size (1.76 mm) compared with Cave-in-Rock (1.34 mm, P < 0.05), but smaller compared with Alamo (2.09 mm, P < 0.05). The IVDMD of the diet selected from Performer was greatest (665 g kg–1), compared with either Cave-in-Rock (560 g kg–1, P < 0.05) or Alamo (607 g kg–1, P < 0.05), whereas NDF concentrations were similar between Performer and Alamo (687 and 685 g kg–1, respectively), but greater for Performer compared with Cave-in-Rock (670 g kg–1, P < 0.05).
Examination of the particle size classes of large ( 
1.7 mm), medium ( < 1.7 and > 0.50 mm), and small ( < 0.50 mm) showed Performer and Alamo switchgrass to have a similar proportion of the dry matter as large (53.2 and 55.2%, respectively) and medium (33.0 and 32.1%, respectively) particles and Performer had a greater (P = 0.05) proportion of large particles and a lesser (P < 0.05) proportion of medium particles compared with Cave-in-Rock (35.7 and 44.9%, respectively). Performer was intermediate in its proportion of small particles. Strikingly, the greatest (P < 0.05) IVDMD was noted for Performer for all three particle-size classes averaging 656, 666, and 689 g kg–1 for the large, medium and small particles, respectively. This compares with 538, 561, and 595 g kg–1, respectively, for Cave-in-Rock and 599, 605, and 642 g kg–1, respectively, for Alamo. The NDF concentrations were similar among Performer and the two cultivars for all three particle-size classes (NDF ranges for large, medium, and small were 695–703, 675–691, and 599–628 g kg–1, respectively). The superiority of Performer in IVDMD, and hence, nutritive value, was further documented by evaluation of the dry matter for each individual sieve size (i.e., particles retained on a 4.0, 2.8, 1.7, 1.0, 0.5, and 0.25-mm sieve or that passed though the 0.25-mm sieve). The IVDMD of Performer particles was greatest among the three cultivars, being as high as 700 g kg–1 for the very finest-sized particles ( < 0.25 mm) and never falling below 650 g kg–1 for the other size particles. On the other hand, Cave-in-Rock had lowest IVDMD and values only exceeded 600 g kg–1 for the very finest-sized particles and fell below 520 g kg–1for the largest particles. Alamo, although greater in IVDMD compared with Cave-in-Rock, was much inferior to Performer, with IVDMD greater than 650 g kg–1 for only the finest-sized particles, with the rest of the particle sizes falling below 620 g kg–1. These data support greater daily digestible dry matter intake and, hence, greater daily animal responses from Performer compared with the two commercial checks.
Performer is an eight-clone synthetic that provides digestibility significantly improved versus that of Cave-in-Rock and Alamo. The area of adaptation is primarily the Southeastern U.S. Seed of Performer has been deposited in the National Center for Genetic Resources Preservation (NCGRP, USDA-ARS). Breeder seed of Performer is being maintained by the North Carolina Agricultural Research Service, Box 7620, N.C. State University, Raleigh, NC 27695. U.S. Plant Variety Protection will not be sought for Performer. At time of submission, Ernst Conservation Seeds, Meadville, PA/Garrett Seed Farm, Smithfield, NC has been granted exclusive rights to produce and market Peformer switchgrass through contractual agreements with the North Carolina Agricultural Research Service. Seed requests for other research purposes (variety testing, etc.) should be directed to the corresponding author, and such seed will only be distributed under a Material Transfer Agreement. Seed of this release is deposited in the National Plant Germplasm System where it will be available after 20 years for research purposes, including development and commercialization of new 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 February 20, 2007.
References
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