ABSTRACT
Summary Objectives of this research were to study the performance of eight populations of D. uncinatum and ten populations of D. intortum, with relation to morphological and agronomic characters; to estimate the genetic variation between populations and between plants within populations; and to estimate genetic and phenotypic parameters for these characters. The experiment was conducted at the National Research Center for Dairy Cattle (EMBRAPA), Minas Gerais, Brazil. It was set up in a randomized complete-block design, with 10 replications. The plots, composed of the two species, were subdivided in 18 subplots. Each supblot contained 4 individual plants spaced 1.5 m apart. The following characters were evaluated at the beginning of the flowering period: length of main stem (LMS), number of lateral branches (NLB), dry-matter percentage (DMP), fiber content (FC), and crude-protein percentage (CPP). Results obtained in analysis of variance showed significant differences between species for the characters LMS, NLB, DF, DMY, and CPP. In addition, significant differences were observed for all characters analyzed in D. uncinatum. In D. intortum there were populations that differed only in respect to LMS, DF, DMY, and DMP. Analysis of variance within subplots indicated the largest variability among plants within populations for DF. On the other hand, as values of the coefficient of genotypic determination (b) were higher in D. uncinatum, it should be easier to obtain changes through selection in the populations of that species than in D. intortum. On the basis of the b values, DF, FC, and CPP are expected to be the characters more easily alterable by selection in D. uncinatum.
