ABSTRACT: The phenotypic and genetic analysis of apple (Malus × domestica Borkh) genotypes is essential for breeding species. Information on the morphology and genetic structure of apple offers significant help for germplasm maintenance and selection of suitable material to breed superior cultivars. This study shows the results of an investigation on the morphology and the genetic diversity for 19 apple cultivars, which are preserved in an ex situ collection in Naoussa, Central Macedonia, Greece. Information was recorded over a 5-year period for 47 traits describing plant morphology and phenotype, as well as leaf and fruit quality. Data were analyzed using the principal component analysis (PCA) method. The Euclidean distance metric and the Ward’s agglomeration method were used in an unsupervised hierarchical cluster analysis of all cultivars. The cultivars were grouped into four main clusters, suggesting that the characterized apple collection has a high potential for specific breeding goals. Furthermore, the cultivars were genotyped using seven microsatellite primers. Moderate levels of polymorphism were detected, and 38 distinctive alleles (5.4 alleles per primer pair) were identified. Both multivariate clustering approach (phenotypic data) and the genetic distance clustering approach (genetic data) grouped the apple cultivars according to their type. Hence, these data could be used for protection or patenting processes of existing or new apple cultivars carried out by the EU-Community Plant Variety Office.

Enxertia é usada no melhoramento da produção, da qualidade do fruto e na resistência `a doenças em espécies vegetais arbóreas. Os mecanismos moleculares sobre as respostas à enxertia estão sendo delineados somente agora. Um deles envolve a transferência a longa distância de material genético do porta-enxerto ao enxerto, aludindo a um componente epigenético para o processo de enxertia. Nesta pesquisa foram investigadas as mudanças herdáveis no padrão de metilação de DNA de genomas de enxertos de solanaceae, em enxertia interespecífica com Cucurbitaceae. As mudanças na metilação de DNA global em enxertos de pepino, melão e melancia, heteroenxertados em porta-enxertos de moranga, foram examinadas usando análise MSAP. Ocorreu incremento significativo de metilação de DNA em pepino e melão, apontando para um efeito epigenético em Cucurbitaceae heteroenxertadas. A exploração do marcador epigenético diferencial em diferentes combinações de porta-enxertos/enxertos pode levar ao desenvolvimento de marcas epimoleculares para geração e seleção de vegetais enxertados de qualidade superior.

Grafting has been used to improve yield, fruit quality and disease resistance in a range of tree and vegetable species. The molecular mechanisms underpinning grafting responses have only recently started to be delineated. One of those mechanisms involves long distance transfer of genetic material from rootstock to scion alluding to an epigenetic component to the grafting process. In the research presented herein we extended published work on heritable changes in the DNA methylation pattern of Solanaceae scion genomes, in Cucurbitaceae inter-species grafting. Specifically, we examined global DNA methylation changes in scions of cucumber, melon and watermelon heterografted onto pumpkin rootstocks using MSAP analysis. We observed a significant increase of global DNA methylation in cucumber and melon scions pointing to an epigenetic effect in Cucurbitaceae heterografting. Exploitation of differential epigenetic marking in different rootstock-scion combinations could lead to development of epi-molecular markers for generation and selection of superior quality grafted vegetables.