SCREENING KENTUCKY-BLUEGRASS FOR ALUMINUM TOLERANCE

Aluminum (Al) toxicity is a growth-limiting factor in acid soils for many turfgrasses. The genetic diversity among turfgrass cultivars for Al tolerance is not well known. One hundred-fifty Kentucky bluegrass (Pea pratensis L.) genotypes (cultivars, selections, and breeding lines) belonging to seven ecotypes were selected to screen for Al tolerance under greenhouse conditions using solution culture, sand culture, and an acid Tatum subsoil (Clayey, mixed, thermic, typic, Hapludult). This soil had 69% exchangeable Al and a pH of 4.4. An Al concentration of 320 mu M and a pH of 4.0 in a modified 1/4 strength Hoagland nutrient solution was used in solution screening and sand screening. The grasses were seeded and grown four to five weeks before harvesting. Differences were identified among cultivars and the seven ecotypes by measuring relative growth. 'Battan', 'Viva', and 'Nassau' were the most Al-tolerant cultivars based on the rank average of the three screening methods. Among the seven ecotypes, BVMG, which refers to cultivars such as 'Baron', 'Victa', 'Merit', and 'Gnome', were most Al tolerant while Midwest ecotypes, which are frequently referred to as common Kentucky bluegrasses, consistently exhibited the least Al tolerance. The results indicate that the Kentucky bluegrass cultivars vary genetically in Al tolerance and that there is potential to improve such tolerance with breeding and to refine cultivar-specific management recommendations regarding soil pH.