High-energy alfalfa (Medicago sativa L.) developed by recurrent phenotypic selection for nonfiber carbohydrate concentration in stems

Abstract

In forages, genetic improvement in readily fermentable energy can improve the energy-to-protein balance, thus reducing N losses to the environment. This study aimed to evaluate the effects of recurrent selection targeting high nonfiber carbohydrate (NFC) concentrations in alfalfa stems on nutritive value and biomass yield. Populations developed after one to three cycles of recurrent selection for NFC (NFC1, NFC2, and NFC3) and a control population (NFC0) were evaluated in a field trial at three sites across Canada, and in a greenhouse trial along with the population developed after a fourth cycle of selection for NFC (NFC4). When comparing NFC3 to NFC0, increases in NFC concentration of 14 and 28 g kg⁻¹ dry matter (DM) were observed in field and greenhouse trials, respectively. This increase reached 45 g kg⁻¹ DM for NFC4 compared to NFC0 in the greenhouse trial. Crude protein (CP) concentration was similar among populations in both trials, resulting in an increase in their NFC/CP ratio. Fiber concentrations were lowered, which resulted in an increase in in vitro DM digestibility of more than 10 g kg⁻¹ DM for NFC3 in the field and for NFC4 in the greenhouse trials, as compared with NFC0. None of the selected populations displayed significant annual yield differences. The recurrent phenotypic selection for high stem NFC concentrations is an effective approach to improve alfalfa NFC concentration while increasing its energy-to-protein balance and digestibility, and maintaining its biomass productivity.