Morphology of Alfalfa Divergently Selected for Herbage Lignin Concentration

Abstract

Programs to improve alfalfa (Medicago sativa L.) nutritive value have used selection criteria based on total herbage cell‐wall composition. There is only limited information addressing the effect of total‐herbage based phenotypic selection on changes in dry‐matter partitioning of the plant and on the nutritive value of plant parts. The objective of this study was to determine the effects of divergent herbage selection for alfalfa cell‐wall components on plant morphology. Two groups of germplasm were observed. Group 1 consisted of six syn‐2 lines derived from two‐parent combinations, which were randomly selected from ‘Saranac‐AR’ for high (HL) or low (LL) herbage acid‐detergent lignin concentration. Group 2 had HL and 13 LL lines that were full‐sib lines produced on pairs of parents from the Group 1 synthetics. Group 1 was grown for two harvests in a greenhouse and one harvest in the field, and Group 2 was grown for two harvests in the field. Compared with HL lines, LL lines had a greater leaf‐to‐stem ratio, especially in the fraction above the sixth node from the stem base. For LL lines, this ratio in the upper plant fraction was 53, 26, and 18% greater than HL lines for Group I greenhouse, Group 1 field, and Group 2, respectively. When harvested at the same time, LL lines were less mature than HL lines, and, for Group 2, main stem length of LL lines was about 30 mm shorter than HL lines. Dry‐matter yield of HL lines was 17, 28, and 28% greater than LL lines for Group 1 greenhouse, Group 1 field, and Group 2, respectively. Most of the differences between divergent types were related to changes above the sixth node. Thus, selection for improved nutritive value in total herbage of alfalfa may result in marked changes in plant morphology.

In vitro ruminal undegradable proteins of alfalfa cultivars

“…1a). This suggests that selection on the basis of one of the nutritive value parameters would affect LWR, which agrees with other studies (Kephart et al 1989).…”

“…Several studies also reported no correlation or weak correlations between digestibility and DMY when cultivars or lines were compared on a single sampling date corresponding to a normal harvesting date (Heinrichs et al 1969;Hill and Barnes 1977;Sunberg et al 1983;Coors et al 1986;Julier and Huyghe 1997). Other studies, however, reported a reduced forage DMY as a result of selection for improved nutritive quality (Kephart et al 1989).…”

Effect of Acid Detergent Lignin Concentration in Alfalfa Leaves on Three Components of Resistance to Alfalfa Rust

“…Breeding alfalfa for increased digestibility is a promising means to increase the nutritive value of forages (4,10,11,14,20,21,23). Both public and private alfalfabreeding programs routinely employ ADL as a selection criterion that is related to digestibility.…”

“…An important fraction of the potential energy from alfalfa forage is unusable by ruminants due to the limited digestibility of cell walls (4,5,(7)(8)(9)(10)23). The plant cell wall is a complex matrix composed of polysaccharides, proteins, phenolics (including lignin), water, and minerals (7).…”

Genetic Improvement of Switchgrass and Other Herbaceous Plants for Use as Biomass Fuel Feedstock

“…Direct selection in forages for cell wall components has been conducted less frequently than for IVDMD or NDF concentration. Alfalfa was selected for low and high ADL concentrations (Hill 1981), but because selection was imposed on total herbage the observed changes in ADL were primarily caused by shifts in leaf-to-stem ratio between the low and high ADL selection lines (Kephart et al 1989(Kephart et al 1990. Selection in corn or maize (Zea mays L.) vegetative tissue for divergent concentrations of ADF resulted in genetic alteration of NDF, ADF, and ADL concentrations for both leaf sheath and stem tissues (Buendgen et al 1990).…”