Assessment of Genetic Variability of Cell Wall Degradability for the Selection of Alfalfa with Improved Saccharification Efficiency

Abstract Alfalfa (Medicago sativa L.) has a high potential for sustainable bioethanol production, particularly because of its low reliance on N fertilizer. We assessed near-infrared reflec-tance spectroscopy (NIRS) as a high-throughput technique to measure cell wall (CW) degradability in a large number of lignified alfalfa stem samples. We also used a powerful immu-nological approach, glycome profiling, and chemical analyses to increase our knowledge of the composition of CW poly-saccharides of alfalfa stems with various levels of degradabil-ity. NIRS accurately predicted CW degradability in four different alfalfa cultivars, as assessed by glucose released following enzymatic saccharification (R200.94). There was a large genetic diversity for enzyme-released glucose. The 10 genotypes with the highest (D+) and 10 genotypes with the lowest (D−) amounts of enzyme-released glucose of a biomass-type (Orca) and a winterhardy-type (54V54) cultivar were further characterized. Glycome profiling showed that there were very few differences in CW polysaccharide com-position between the two groups, although the D+ genotypes were at least 35 % more degradable than the D − genotypes. Determination of CW composition by chemical analyses showed that a higher lignin content of the D − genotypes was closely related to their lower enzyme-released glucose (R0−0.83). In each cultivar tested, 20 D+ genotypes and 20 D − genotypes were intercrossed to generate D+ and D − pop-ulations. Assessment of CW enzyme-released glucose in the progenies showed that this trait is genetically inherited. The large genetic diversity for enzyme-released glucose and its potential for selection support the huge potential of alfalfa for the sustainable production of bio-ethanol