VARIAÇÃO E PARÂMETROS GENÉTICOS EM DOIS BANCOS DE GERMOPLASMA DE Tabebuia heptaphylla (Velloso) Toledo

Abstract

The aim of this study was to investigate the genetic variation and to estimate genetic parameters for growth, form and survival traits at 22 and 21 years of age in two progeny tests of Tabebuia heptaphylla, established in Luiz Antônio Experimental Station, belonging to the Forestry Institute of the State of São Paulo. The test I was established with 19 progenies from Bauru provenance and the test II by 15 progenies from Assis provenance. Significant differences among progenies were observed in the test I for form and survival and in test II for survival. The survival in both tests was relatively high (> 77%), indicating that both populations present good adaptation to environmental condition of Luiz Antônio. The coefficient of genetic variation ( CV_g ) was generally low (≤ 4.6%), suggesting that the adopted sampling strategy to conserve the genetic variation of the populations was not efficient or both population have low genetic variation. The coefficients of heritability at individual plants ( h²_d ) and within progenies levels ( h²_i )were equally low (maximum of 0.09). The coefficient of heritability at progeny means level (h²_m ) was high for stem form (minimum 0.43) and survival (0.78), showing that both tested material have genetic potential for selection. The estimative of the status number before the selection in test I and II indicated that the 570 and 450 individuals, respectively, correspond to 39 and 31 not endogamic and relative trees. After selection of six plants per progeny, the status number was reduced and the 114 and 90 selected trees in test I and II, respectively, correspond to 32 and 25 trees non endogamic and without relatedness. In general terms, the results indicated that low genetic variation and small status number was retained in both germoplasm banks.