Análise dialélica na avaliação do potencial de híbridos de Pinus elliottii x Pinus caribaea para a formação de populações de melhoramento

Abstract

Uma das dificuldades no melhoramento florestal é o longo ciclo de seleção de materiais genéticos superiores em qualidade e produtividade, problema que pode ser contornado via seleção precoce de híbridos. O objetivo da presente pesquisa foi estimar os parâmetros genéticos para caracteres silviculturais e verificar a viabilidade da seleção precoce em híbrido de Pinus elliottii x Pinus caribaea, visando a formar uma população base de melhoramento. O experimento foi estabelecido em delineamento em blocos ao acaso, com seis blocos, parcelas lineares de seis plantas e 24 tratamentos (21 progênies de polinização controlada e três testemunhas). Os caracteres diâmetro à altura do peito (DAP) e altura total (H) foram avaliados no quarto e oitavo ano após o plantio. Os quadrados médios referentes às capacidades geral (CGC) e específica (CEC) de combinação foram significativos para a H aos quatro e oito anos e para DAP aos oito anos. As diferenças significativas entre os tratamentos indicam a existência de variação genética, sugerindo a possibilidade de ganhos com a seleção. As correlações genéticas entre caracteres e entre idades foram altas, variando de 0,96 a 0,99, indicando que a seleção precoce pode ser uma ferramenta efetiva para implantação de uma população de melhoramento para o híbrido.

Selection of Pinus spp. progenies in Lavras (Minas Gerais, Brazil) at 36 months of age

“…According to the classification of Resende (2002), heritabilities below 0.15 were classified as low magnitude, heritabilities between 0.15 and 0.50 are classified as intermediate magnitude, and heritabilities above 0.50 are classified as high magnitude. The heritabilities observed were similar to those obtained by Tambarussi et al (2010), Souza et al (2017) and Tambarussi et al (2018) and are higher than those reported by Silva et al (2011).…”

“…The progenies of Pinus caribaea var. hondurensis had results similar to those reported by Durigan et al (2004) in Assis, São Paulo, at three years after planting; by Donadoni et al (2010) in Vilhena, Rondônia, at three years of age and by Tambarussi et al (2018) in Canoinhas, Santa Catarina, at four years after planting. The latter observed an average of 5 cm DBH, 4 m H and 1.63 m² plant -1 CPA, which demonstrates the potential of the tested progenies for the region of Lavras.…”

“…These results favored the use of indirect selection, where progenies ranked with high DBH values consequently showed high H values (Sebbenn et al 2010). Consistent with these results, Tambarussi et al (2018) found a strong genetic correlation between DBH and H (0.84). For the correlation between CPA and DBH or H, intermediate phenotypic and environmental correlations were observed, which indicates that these variables are similarly influenced by the environment, as the correlation corresponding to environmental causes is considered the total effect of all the variable factors in the environment that caused a positive correlation (Falconer & Mackay 1996).…”

“…variation present in the total phenotypic variance, which according toSouza et al (2017), estimates the reliability of the phenotypic value as an indicator of reproductive value; for this reason, the mentioned heritabilities are frequently included in expressions aimed at gain prediction, which in turn assists breeders in making decisions in genetic improvement programs.Resende & Duarte (2007) reported that, to promote selection and recombination for plant breeding, recommended selection accuracy values are above 0.70. The selective accuracy values were similar to those obtained byTambarussi et al (2018), who selected Pinus elliottii x Pinus caribaea hybrids at four years after planting and found an accuracy of 0.91 for DBH and 0.93 for H Souza et al (2017),. working with Pinus caribaea var.…”

“…Direct selection performed on one trait can affect gains in other traits (Missio et al 2004). When selecting Pinus elliottii x Pinus caribaea hybrids using DBH, Tambarussi et al (2018) noted that the genetic correlations indicated probable positive selection effects for both DBH and H as well as for tree CPA (Falconer & Mackay 1996). These results suggest that selection using the FIGURE 2: Gains from selection for DBH, H and CPA using the direct method and the method of Mulamba & Mock (1978) for progenies of Pinus caribaea var.…”