Características atômicas, morfofisiológicas, químicas e biológicas de lâminas foliares de genótipos de Panicum maximum

Abstract

The experiment was carried out at Embrapa Beef Cattle, in Campo GrandeMS and in the forage laboratory of UFGD, in Dourados-MS, from January to November 2007. Twenty-three Panicum maximum genotypes pre-selected from the Embrapa Beef Cattle breeding program were evaluated. The objective of this research was to verify which of the easily measurable and low cost anatomical and morphophysiological characteristics were most correlated with the chemical and biological ones, and may discriminate the most promising genotypes as to nutritive value in the initial phases of the process of selection and breeding and also which is the best method of grouping of genotypes. The experimental design used was a randomized blocks design with three replications, and 12m2 plots. Two harvests were done during the rainy season for the anatomical and morphophysiological evaluations of leaf blades. Simple linear correlation analysis (138 observations per characteristic) and canonic correlations between the anatomical, morphophysiological, chemical and biological characteristics were done using the statistical program SAS (SAS Institute, 1998). For each character studied the mean grouping test Scott-Knott was used. For the genetic divergence of the evaluated genotypes, the grouping methods of Tocher and of nearest neighbor were used, based on the generalized distance of Mahalanobis and analysis of graphic dispersion of canonic variables. All the analysis were done using the computational program GENES. The anatomical characteristics: adaxial epidermis, abaxial, adaxial + abaxial, mesophile and vascular tissue + schlerenquima, and the morhophysiological: specific leaf area and length, were the ones that best discriminated the genotypes. The bundle sheath cells (BPF) and width presented phenotypic instability not being recommended to discriminate the groups of genotypes. The genotypes which outstanded as to their quality potential, based on their anatomy were: cv. Aruana, PM42, PM43, PM45, PM47 and cv. Tanzânia. As to the morphophysiological characteristics, the genotypes cv. Aruana, PM31, PM37, cv. Massai, PM38, PM42, PM43, PM44, PM45, PM46 and cv. Tanzânia presented the largest specific leaf areas. Therefore, for this research, the best genotypes were: cv. Aruana, PM42, PM43, PM45 and cv. Tanzânia. Of the multivariate analysis, the methods of Tocher explained better the grouping of the genotypes.