Principal component analysis applied to the study of yield and nutritional characteristics of forage cultivars

The objective of this study was to evaluate the importance of various yield and nutritional characteristics for the differentiation of forage cultivars using principal component analysis (PCA). Data were obtained from an experiment conducted with a complete randomized block design (RCBD) with 6 replications. Eleven cultivars of forage grasses of the species Urochloa brizantha, U. ruziziensis, Megathyrsus maximus, Cenchrus ciliaris, Andropogon gayanus and Setaria sphacelata were evaluated. For yield characteristics, PCA revealed that the first 3 components explained 82.0% of total variation between forage cultivars. Similar results were observed for nutritional characteristics with the first 3 components explaining 91.4% of total variation in leaf chemical composition and 83.8% of variation in stem chemical composition. Variables that contributed most to discrimination between forage cultivars were: number of tillers per plant; number of leaves per plant; median leaf width; stem dry matter yield; leaf:stem ratio; % dry matter, % crude protein (CP) and % neutral detergent fiber of leaves; and % CP, % ether extract and % acid detergent fiber of stems. PCA was effective in identifying the key parameters that need to be measured in evaluating grass species and allowed a reduction in the number of yield and nutritional characteristics to be assessed in experiments designed to evaluate forage cultivars. This reduced both the workload and the costs involved while still allowing valid conclusions.