Application of canonical discriminant analysis for the assessment of genetic variation in tall fescue

Tall fescue pastures are perennial in habit and are continually exposed to intensive natural selective forces. Therefore, the genetic composition of tall fescue cultivars changes with time and the selection is cumulative. The objective of this study as to investigate the genetic diversity of tall fescue cultivars and age groups within cultivars in response to natural selective forces using a multivariate statistical method. canonical discriminant analysis. Ungrazed survivors from four cultivars (GA-5 EF, GA-5 EI, Johnstone, and KY-31) were collected randomly from four 1-yr-old paddocks. These paddocks were then grazed at 2.50, 3.75, 5.00, and 6.25 Angus yearling steers ha 1 for 2 yr, and grazed survivors were collected in a similar fashion as that of ungrazed sur hors. The ungrazed and grazed groups were compared in a 2-yr stud. along with plants grown directly from the original seed lots. Significant genetic diversity was noticed among these four tall fescue cultivars and clearly depicted the relationship of cultivars by ancestry and endophyte status. Significant genetic diversity between GA-5 EF and GA-5 EI indicated that the removal of endophyte resulted in a different cultivar with altered morphological and agronomic characteristics. Significant genetic diversity was observed among the age groups in GA-5 EF, GA-5 EI. and Johnstone. The age groups of KV-31 were stable in terms of genetic variation. These results indicated that changes in genetic variation occurred in a short period of time, that is, 3-yr old paddocks of GA-5 EF, GA-5 EI. and Johnstone.