Portal de Periódicos da CAPES

Breeding for root yield in alfalfa

1991; Canadian Science Publishing; Volume: 71; Issue: 3 Linguagem: Inglês

10.4141/cjps91-106

1918-1833

G. Saindon, R. Michaud, C. St-Pierre,

Genetics and Plant Breeding

Winter survival of alfalfa (Medicago sauva L.) has often been associated with the size of the root system but breeding for a larger root system has never received much attention. The objectives of this study were to detect variability for root traits among seven alfalfa entries grown under two nitrogen fertilizer treatments (R- and N-treatments) which consisted of Rhizobium nitrogen fixation and inorganic nitrogen fertilizers, respectively; to select for root yield in two alfalfa cultivars grown under the same two treatments and to measure resulting progress; and to determine which of the two N regimes is more appropriate for root yield selection. Variability for root yield, number of laterals, crown width and top yield was found among R-treated entries whereas only the crown width varied among the N-treated ones. The evaluation under both treatments showed that one cycle of bidirectional phenotypic selection made under both the R- and N-treatments was sufficient to allow the formation of divergent populations for root yield with the exception of Apica-derived populations which showed inconsistent or no responses when evaluated under the N-treatment. Independently of the cultivars and treatments used for selection and evaluation, asymmetries of response were observed. Possible explanations are proposed but additional cycles of selection are needed to provide definitive conclusions. Indirect selection responses observed for top yield, crown width, and root branching should make selection for increasing root yield in alfalfa attractive. Key words: Medicago sativa L., root branching, realized heritability, asymmetry of response, indirect response