Avaliação de clones de Pennisetum purpureum Schum. de porte baixo, na Zona da Mata de Pernambuco

Abstract

The experiment was carried out at the Experimental Station of Itambé, from the Pernambuco Agricultural Research Enterprise (IPA), aiming to evaluate different morphologic descriptors and the chemical composition of different dwarf clones of Pennisetum sp. as well as to estimate the heritability of several characters. Nine clones of dwarf elephant-grass were used (Taiwan A.146 - 2.14, Taiwan A.146 - 2.27, Taiwan A.146 - 2.37, Taiwan A.146 - 2.114, Merker México - 6.2, Merker México - 6.5, Merker México - 6.31, cv. Mott, CNPGL92F198.7). The experimental area was established in the beginning of April/2005. It was used vegetative propagation, using stem fractions. The experimental design used was randomized blocks with three replications. It was performed a manual staging cut at 10 cm from ground level, in May of 2005, followed by five cuts with 60 dayintervals at 10 cm from ground level. The morphologic descriptors were applied after 60 days of the staging cut. At the harvest time, the clones were characterized morphologically, and two types of estimates were used: grading scale through visual observations(descriptors) and direct measures (direct in the plant). An indirect measurement of character desirability was also performed. For the study of the chemical composition, it was utilized the clones that survived from the morphologic evaluations. All clones presented semi-erectleaves, with grading average of 3,73, except for the clone Taiwan A.146 - 2.37 that presented tendency to have more erect leaves. Regarding the intensity of basal tillering, the clones Merker México - 6.2, Merker México - 6.5, and Taiwan A.146 - 2.14 presented the smallest grades (3.93, 3.93, and 4.40, respectively). The intensity of axial tillering was absent in the clone Merker México - 6.2 with grade 1.93, medium for the clone Taiwan A.146 - 2.37 which received grade 5.66, and low for the remaining clones. In a general way, average intensity of total tillering was observed among the clones, indicating that the materials may be used in forage banks as well as under grazing. The tallest plants were the ones that presented larger desirability, therefore, this characteristic should be considered in the selection. The heritability estimate was high for all the appraised characters in dwarf elephant-grass. For DM production, leaf/stem ratio, and the concentration of DM, NDF, andNFC, no differences were observed (P <0.05) among the clones. For leaf CP, the clone Mott(14.1%) was superior to the clone Taiwan A. 146-2.114 (12.0%), but did not differ from other clones. The concentration of TCH and NFC didn't differ (P>0.05) for leaf of dwarf elephant-grass clones under cut at 60 days of regrowth, presenting averages of 74.4 % and 14.8 % for TCH and NFC, respectively. For stem CP, the clone Mott (12.3 %) was superior than clone Taiwan A.146 - 2.27 (9.0 %) and didn't differ from the others. For ADF, the clone Taiwan A.146 - 2.37 (42.0 %) was superior to the clone Mott, not differing from the others. The clones Taiwan A.146 - 2.37, originated from the IPA/UFRPE breeding program, was similar to the Mott cultivar. Heritability values showed genetic variability among clones at 60 days of regrowth. Some morphologic descriptors applied allowed to characterize theevaluated genotypes. The clones Taiwan A. 146-2.27, Taiwan A. 146-2.37, Taiwan A. 146- 2.114, and Merker Mexico 6.31 were taller, showed greater total tillering intensity, and were more desirable. As a results, these clones have greater potential for use under cut.