Eficiência da amostragem de matrizes de Cedrela Fissilis Vell. para melhoramento e conservação genética baseado em caracteres juvenis
Biernaski, Fabrício Antonio
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Conservation of local genetic variability of native forest tree species is important for maintaining the ecological balance of a region, as well as for allowing its future use in tree genetic improvement programs. Red-cedar (Cedrela fissilis Vell.) is a forest tree species of high value-added wood. However, the lack of genetically selected material and adequate silvicultural techniques for the species is a deterrent to its use in commercial forest plantations. Currently, there exists a strong demand of red-cedar saplings for environmental restoration, requiring materials that are both of high genetic variability and representatives of the region to be restored. This work aimed to assess the efficiency of sampling Cedrela fissilis trees for genetic improvement and conservation programs. A progeny test was established in a nursery with seeds from 48 sampled trees collected in the municipalities of Rio Negrinho, Mafra and São Bento do Sul, state of Santa Catarina, and in the municipalities of Lapa, Rio Negro, Campo do Tenente and Antonio Olinto, state of Paraná (33 sampled trees distributed among three sites and 15 trees dispersed in the studied region). The experiment was established in a randomized complete-block design, with 8 blocks and 20 plants per plot. The weight of 100 seeds per sampled tree was obtained. The following data were obtained for the saplings: emergency velocity index; sapling base diameter and height (at the intervals of 61, 102 and 145 days after germination); sapling survival; number of leaves per sapling; dried weight of aboveground parts and roots; and the foliar area of the third fully expanded leaf counting from the apical meristem. The Maximum Restricted Likelihood Method (REML) was employed, using the software SELEGEN, to analyze genetic variation among groups of sampled trees, as well as to estimate genetic parameters and to perform gain simulations based on genetic selection. It was verified that the three groups of trees from different sites did not differ significantly, which makes it possible to use their seeds for the purpose of forest restoration in the studied region, without threatening the local gene pool of the species, because the area belongs to the same tree seed transfer zone. The characters evaluated in the nursery have a high genetic control and can be used to assess genetic variability of Cedrela fissilis's populations samples. It was shown that both seed weight and emergency velocity index strongly influenced the initial development of saplings. Over time, however, this influence ceased. Finally, it is possible to conclude that the used sampling design was adequate to capture a wide genetic variability of the area of study, indicating that it is possible to use the genetic material sampled in programs of genetic conservation and improvement of the species.
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