Switchgrass biomass composition altered by six generations of divergent breeding for digestibility.

Biomass composition of switchgrass (Panicum virgatum L.) can affect its utilization by ruminants and its conversion to liquid fuels in a biorefinery. The objective of this study was to evaluate the effects of six generations of divergent breeding for forage in vitro dry matter digestibility (IVDMD) on switchgrass biomass composition, forage quality traits, and ethanol yield. Initially there was one cycle of selection for both low (C-1) and high IVDMD (C1 = cv. Trailblazer), followed by four additional breeding cycles for high IVDMD. In cycles 4 and 5, winter survival was included as a selection criterion because of decreased winter survival of the C3 population. The experimental populations that were produced by these breeding generations and nine half-sib families from cycle 5 were evaluated for two post-establishment years at the research station in eastern Nebraska, where all the breeding work was conducted. The six breeding generations resulted in significant differences among the populations for all the 28 cell wall and non-cell-wall composition variables measured, forage quality, and ethanol yield traits measured except for total biomass C, cell wall concentration, soluble glucose, and etherified ferulates. These traits included all cell wall and nonstructural carbohydrates. Breeding for the heritable complex trait IVDMD affected a large number of plant biomass characteristics and also adversely affected plant biomass yield and winter survival. K.P. Vogel, R.B. Mitchell, and G. Sarath, USDA-ARS, Grain, Forage, and Bioenergy Res. Unit, 137 Keim Hall, Dep. of Agronomy and Horticulture, Univ. of Nebraska-Lincoln, Lincoln, NE 68583-0937; H.G. Jung, USDA-ARS (retired), Plant Science Research Unit and Dep. Agronomy and Plant Genetics, 411 Borlaug Hall, 1991, Upper Buford Circle, St. Paul, MN 55108-6026; B.S. Dien, USDA-ARS Fermentation Biotechnology Res. Unit, National Center for Agricultural Utilization Res., 1815 N. University Street, Peoria, IL 61604; M.D. Casler, USDA-ARS, U.S. Dairy Forage Res. Center, 1925 Linden Drive West, Madison, WI 53706-1108. Mention of trade names or commercial products in this publication is solely to provide specific information and does not imply recommendations or endorsement by the U.S. Department of Agriculture. The USDA is an equal opportunity employer. Received 18 Sept. 2012. *Corresponding author (Ken.Vogel@ars.usda.gov). Abbreviations: ADL, reduced acid detergent lignin; BW IVDMD, in vitro dry matter digestibility; MSFS, multi-step family selection; NIRS, near infrared reflectance spectrometry; RRPS, restricted recurrent phenotypic selection; SSF, simultaneous saccharification and fermentation; see Table 2 for an extensive listing of abbreviations for biomass composition or conversion traits. Published in Crop Sci. 53:853–862 (2013). doi: 10.2135/cropsci2012.09.0542 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA 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.