Screening the Alfalfa Core Collection for Acid Soil Tolerance
Since previous work indicated U.S. alfalfa (Medicago sativa ssp. sativa L.) cultivars are limited as genetic sources of acid soil tolerance, new germplasm needs to be identified and used. The objective of this paper was to screen the PI Core Collection for acid soil tolerance in the greenhouse. Initially, 192 of the 200 PIs in the core collection were screened during 1992 and 1993 in Georgia using replicated cups containing a lower zone of unlimed, unfertilized subsoil with an upper seed germination zone containing the same soil, but limed and fertilized. Acid soil tolerance of each PI was estimated by recording the root dry weight entering the unlimed layer and comparing it with an acid soil tolerant check, GA-AT. A repeat study using the same screening procedure with 14 PIs was then performed during 1994. Among these 14, seven had initially shown superior root growth to GA-AT, while seven demonstrated poorer root growth than GA-AT. None of the seven superior PIs were found to possess better root, crown, or top growth compared with GA-AT, while the poor rooting PIs remained inferior to GA-AT for all measured variables. Within the limits of this screening procedure, these findings indicated that germplasm with exceptional acid soil tolerance will be difficult to isolate from the alfalfa PI collection.
Copyright © . .