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

Abstract

As plant breeders select alfalfa (Medicago saliva) genotypes for improved digestibility by ruminants, there may be an increased risk of yield losses due to plant disease. This is because increases in digestibility are often associated with a decrease in lignin content and lignin has been shown to play an important role in plant defense mechanisms against disease and pests. The method most often employed by public and private alfalfabreeding programs to assess digestibility is acid detergent lignin (ADL) analysis. ADL concentration was determined for individual alfalfa plants from two different alfalfa populations. Plants representing a range of ADL concentrations within each population were arbitrarily selected, cloned, and used in experiments to quantify the relationship between leaf ADL concentration and components of resistance to Uromyces striatus, the causal agent of alfalfa rust. Three components of resistance were quantified: infection efficiency (pustules per cm2 leaf area), latent period (the time from inoculation to when 50% of the pustules were visible), and sporulation capacity (the number of urediniospores produced per pustule). Although analysis of variance found significant differences among clones for infection efficiency, latent period, and sporulation capacity, regression analysis revealed little or no relationship between ADL concentration and components of alfalfa rust resistance. F statistics for regression equations and t statistics for slope parameters generally were not statistically significant and when these statistics were significant, coefficients of determination (r2) values indicated that ADL concentration explained only 23% or less of the variation in resistance components. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. As plant breeders select alfalfa (Medicago sativa) genotypes for improved digestibility by ruminants, there may be an increased risk of yield losses due to plant disease. This is because increases in digestibility are often associated with a decrease in lignin content and lignin has been shown to play an important role in plant defense mechanisms against disease and pests. The method most often employed by public and private alfalfa-breeding programs to assess digestibility is acid detergent lignin (ADL) analysis. ADL concentration was determined for individual alfalfa plants from two different alfalfa populations. Plants representing a range of ADL concentrations within each population were arbitrarily selected, cloned, and used in experiments to quantify the relationship between leaf ADL concentration and components of resistance to Uromyces striatus, the causal agent of alfalfa rust. Three components of resistance were quantified: infection efficiency (pustules per cm 2 leaf area), latent period (the time from inoculation to when 50% of the pustules were visible), and sporulation capacity (the number of urediniospores produced p...

An investigation on improved source population for the alfalfa (Medicago sativa L.) breeding

“…Among genotypes, Cay-2 (7.41%), Yalvac-3 (7.37%), Sandıklı-2 (7.33%), Yesilova-1 (7.46%), Keciborlu3 (7.48%), G.Dost-1 (7.49%), Bucak-3 (7.65%) and Sandikli-1 (7.68%) genotypes had less ADL content compared with the other alfalfa genotypes (between 8.54-7.83 %). Lignin ensures strength to plants and allows the plant vascular system to transport water in the plant without leakage (Webb et al, 1996). Along with that lignin increasesd with advanced maturity in alfalfa.…”

Responses to Divergent Selection for Fiber Concentration at Two Disease Potentials in Smooth Bromegrass

“…Breese and Davies (1970) reported that successful divergent selection for WSC in perennial ryegrass ( Lolium perenne L.) for three generations resulted in higher susceptibility to crown rust infection (caused by Puccinia coronata Corda) for the families with high WSC. Webb et al (1996) reported that plants selected for low ADL in alfalfa ( Medicago sativa L.) showed greater susceptibility to alfalfa rust (caused by Uromyces striatus J. Schröt.)…”

Reactions of Smooth Bromegrass Clones with Divergent Lignin or Etherified Ferulic Acid Concentration to Three Fungal Pathogens

“…Schröt., the causal agent of alfalfa rust. Although there were significant differences among clones for infection efficiency, latent period, and sporulation capacity, there was little or no relationship between lignin concentration and components of alfalfa rust resistance (Webb et al, 1996).…”