Masters Theses

Date of Award

5-2014

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Fred L. Allen

Committee Members

Hem S. Bhandari, Dennis R. West, Arnold M. Saxton

Abstract

Switchgrass (Panicum virgatum L.) is widely accepted as a forage crop throughout the United States. It is known for its performance on field sites that may be marginal for row crop production and as a warm season grass to fill gaps for cool season forages. With the increase of fuel and fertilizer costs, forage producers need higher yields and better quality than ever before. The objectives of this research were to: (i) compare four F1 [first generation] half-sib populations for their potential of producing superior lines for forage production, (ii) assess the genetic variances for yield, and (iii) evaluate correlations between yield and other agronomic traits for the purpose of indirect selection. The four parental lines were PI 421999 (AR), PI 607837 (TX), Cimarron (OKS), and NSL-2001-1 (OKN). Seed for one hundred and forty F1 half-sib progeny were produced in a polycross nursery at the East Tennessee Research and Education Center (ETREC), Plant Sciences Unit, Knoxville and planted in 2009. The parents and half-sibs were evaluated at the ETREC, Holston Unit in 2012 and 2013. Data were collected and analyzed on forage yield and nutritive value traits such as protein content, acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and relative feed value (RFV). Early-season yields of the F1 half-sib populations ranged between 1.00 and 1.08 kg plant-1[per plant] in 2012 and 1.41 and 1.51 kg plant-1 in 2013. Genetic variance for yield was not exhibited on a population basis, but was identified in five sub-families in 2012 and ten sub-families in 2013, three sub-families showing genetic variance for yield for both years. The average protein content of populations ranged between 10.3 and 10.8 % [percent] in 2012 and 10.2% for all populations in 2013 for the early-season harvest. The average protein content of the populations for the late-season harvest ranged from 8.1 to 8.6% in 2012 and 9.7 to 10.5% in 2013. ADF ranged from 36.7 to 43.3% and NDF ranged from 73.6 to 79.9% over the two harvests of each year. Moderate correlations were found between yield and: height and canopy regrowth density.

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