Field assessment of alfalfa populations recurrently selected for stem cell wall digestibility
Citation
Bertrand, A., Claessens, A., Thivierge, M.N., Rocher, S., Lajeunesse, J., Castonguay, Y., Seguin, P. (2018). Field assessment of alfalfa populations recurrently selected for stem cell wall digestibility. Crop Science, [online] 58(4), 1632-1643. http://dx.doi.org/10.2135/cropsci2018.02.0119
Plain language summary
This paper describes the progress of our work aimed at developing an alfalfa variety with reduced lignin content and increased digestibility using conventional breeding techniques (non-GMO). The paper first describes our method of selecting the best genotypes and crosses to obtain new, more digestible populations. It then describes the field trials carried out to confirm the validity of our approach. The populations obtained after two cycles of selection had a digestibility that was 15% higher than the initial populations at all three sites during the three years of the study. Important traits such as yield, winter survival and energy content of the plants were not affected by selection. In conclusion, recurrent selection for the stem digestibility approach that we have developed is an effective way to increase the fermentable energy of alfalfa for ruminant nutrition.
Abstract
Genetic variability for stem cell wall (CW) digestibility could be exploited to improve rumen-fermentable energy in alfalfa (Medicago sativa L.) forage. We evaluated in the field the response to recurrent selection for stem CW digestibility in alfalfa. Digestibility was assessed as the concentration of glucose released after enzymatic hydrolysis of fiber (enzyme-released glucose, ERG). Two initial cultivars, 54V54 and Orca, and populations obtained after successive cycles of divergent selection for stem CW digestibility (D−1, D−2, D+1, and D+2) were established at three field sites in north, central, and south of Québec. Field trials conducted over two growing seasons showed that populations obtained after two selection cycles (D+2) had significantly higher CW digestibility (+20.7 mg ERG g−1 CW) than initial cultivars (average of 13% improvement of digestibility). The D+2 populations did not differ from the initial cultivars with regard to biomass yield, winter survival, and stem water soluble-carbohydrate concentration. Increases of ERG concentrations were observed in response to each selection cycle, and broad-sense heritability highlights a moderate control of genetic factors over environmental factors for CW digestibility. Recurrent selection for stem CW digestibility is a valuable approach to increase fermentable energy in alfalfa forage and improve N utilization by ruminants.