Avaliação de características morfológicas e comparação de métodos de estimativas de índice de área de cladódio na palma forrageira

Abstract

The experiment was accomplished at the Experimental station of Caruaru belonging at Instituto Agronômico de Pernambuco, aiming to evaluate the relationship among the morphologic and productive characteristics of cactus forage clones, for identification of characteristics related directly to production, as well as to verify the best indirect method for estimating the cladode area index (IAC). The experiment was accomplished using clones from a germplasm bank with a total of 441 cactus clones. A random selection of 50 clones was performed for evaluation in this study. The following plant characteristics were evaluated: plant width, plant height, cladode area index (IAC) by two methods (regression equation and contours accomplished in papers), growth habit, presence of hair and thorns. The following measures were performed on the cladodes: cladode length, cladode width, cladode perimeter, cladode thickness, angle,number and size of thorns. It was performed a descriptive statistics analysis of the data as well as path analysis, being considered main dependent variable the dry matter production (t/ha/2years). As explanatory independent variables, the following variables were used: average plants height (AP), plant width (LP),width of the primary article (LA1), width of the secondary article (LA2), length of the primary article (CA1), length of the secondary article (CA2) and thickness of the tertiary article (EA3). The variables presented positive correlations, ranging from low to high magnitude; however, significant results were obtained just for plant height, plant width, width of the primaryarticle and length of the primary article. The plant height presented larger correlation with the dry matter production (r = 0,61), however, its contribution for the dry matter production through direct effect showed low magnitude. This fact indicates that other characteristics are influencing the correlation, being necessary to the association of plant height with other characteristics seeking to the production of dry matter. The association of the characteristic plant height with plant width promoted high correlation phenotypic (0,71) and larger direct effect (0,69) in the production of dry matter exhibiting strong influence in the expression of this characteristic. The most efficient methodology for the obtaining the IAC was for the contour of the cladodes in paper leaves, even so, it requests time for execution of the work. Researchers that want to activate the work can use the methodology of regression equation to measure IAC in a satisfactory way