Effect of divergent selection for root size in field-grown alfalfa

The size of the root system as measured by its electrical capacitance was e valuated on two alfalfa (Medicago sativa L.) cultivars (Zuzana, Palava) for 3 yr. Plants with root system size (RSS) significantly larger or smaller t han the cultivar mean were selected and their open-pollinated progenies wer e evaluated in the following 3 yr. Progenies of plants with large RSS tende d to have larger RSS and higher forage yield than progenies of plants with small RSS. The differences for both parameters were significant (P < 0.05) in the case of Zuzana. It is concluded that RSS is a useful selection crite rion in alfalfa breeding.