The Size of the Root System of Lucerne Varieties Grown for Forage and Seed, and its Relation to Yield

The size of the root system as determined by its electrical capacity was evaluated in lucerne plants of two varieties and three new synthetic populations in field experiments during four years (1981–1987). The average size of the root system of plants which were harvested three times, per year for forage was about 11 % smaller than that of plants grown for forage in the primary growth and for seed in the secondary growth of each year. The smallest root system was determined in the variety ‘Bobrava’ and the synthetic population ZE‐S‐VH (relatively 100 and 100.9 %), followed by the variety ‘Palava’ and the synthetic population ZE‐S‐IV (1 05.1 anc 106.7 %). The largest root system was Sound in the synthetic population ZE‐S‐V (111.7%). One of the five parental Tories in ZE‐S‐IV and ZE‐S‐V exhibited significant effects of general combining ability for root system size. The large root system could also be due to higher resistance to vascular wilt. The larger root system is related to higher persistence, stability for more: cuts, higher level and stability of forage and seed yield in comparison to the control variety. The results present evidence for succesfully breeding, lucerne for larger root systems.