RESUMO
Rootstock-induced dwarfing of apple scions revolutionized global apple production during the twentieth century, leading to the development of modern intensive orchards. A high root bark percentage (the percentage of the whole root area constituted by root cortex) has previously been associated with rootstock-induced dwarfing in apple. In this study, the root bark percentage was measured in a full-sib family of ungrafted apple rootstocks and found to be under the control of three loci. Two quantitative trait loci (QTLs) for root bark percentage were found to co-localize to the same genomic regions on chromosome 5 and chromosome 11 previously identified as controlling dwarfing, Dw1 and Dw2, respectively. A third QTL was identified on chromosome 13 in a region that has not been previously associated with dwarfing. The development of closely linked sequence-tagged site markers improved the resolution of allelic classes, thereby allowing the detection of dominance and epistatic interactions between loci, with high root bark percentage only occurring in specific allelic combinations. In addition, we report a significant negative correlation between root bark percentage and stem diameter (an indicator of tree vigour), measured on a clonally propagated grafted subset of the mapping population. The demonstrated link between root bark percentage and rootstock-induced dwarfing of the scion leads us to propose a three-locus model that is able to explain levels of dwarfing from the dwarf 'M.27' to the semi-invigorating rootstock 'M.116'. Moreover, we suggest that the QTL on chromosome 13 (Rb3) might be analogous to a third dwarfing QTL, Dw3, which has not previously been identified.
Assuntos
Mapeamento Cromossômico , Loci Gênicos , Malus/crescimento & desenvolvimento , Malus/genética , Modelos Genéticos , Casca de Planta/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/genética , Ligação Genética , Marcadores Genéticos , Genótipo , Fenótipo , Caules de Planta/anatomia & histologia , Polimorfismo de Nucleotídeo Único/genética , Locos de Características Quantitativas/genética , Estações do AnoRESUMO
O objetivo deste estudo foi testar e selecionar modelos que expressam o volume com e sem casca e determinar o fator de forma e a porcentagem de casca para uma área de floresta ombrófila aberta na região noroeste de Mato Grosso. Foi realizada a cubagem rigorosa de 91 árvores para a obtenção do diâmetro, espessura de casca, altura total do fuste e volume sólido. Dez modelos volumétricos foram testados, sendo que para a seleção do melhor modelo foram usadas as estatísticas do coeficiente de determinação ajustado, erro padrão da estimativa, seguida da análise de resíduos e distribuição gráfica dos resíduos. Os modelos selecionados foram validados pela aplicação do teste L&O. O fator de forma médio obtido foi de 0,7424 e 0,7297 com e sem casca, respectivamente. O volume médio de casca foi de 0,4292 m³ (7,45% do volume total). O modelo de Schumacher-Hall foi o que melhor se ajustou aos dados de volumes com e sem casca.
This study aimed to test and select models, with and without bark volume, and to determine the form factor and bark percentage of an open ombrophylous forest in northwest Mato Grosso. 91 trees were cubed by obtaining diameter, bark percentage, stem height and solid stem volume. A total of 10 models were tested. Statistical procedures, such as adjusted determination coefficient, residual error and distribution of residuals, were tested. The selected models were validated by the L&O test. The average form factor was 0.7424 and 0.7297, with and without bark, respectively. The average volume of bark was 0.4292 m³ (7.45% of total volume). The Schumacher-Hall model showed the best performance for volumes with and without bark.
