Effect of polyploidization on morphology in two apple (Malus x domestica) genotypes

Because polyploidy often results in enhancement of desirable properties, artificial genome doubling is commonly used in agri- and horticultural crop breeding programs. In this study genome doubling was induced in two apple genotypes. The effect on vegetative morphological and physiological traits of the plants was then comprehensively determined by comparing the obtained tetraploid apple plants with their diploid counterparts. Out of 17 different physio- and morphological characteristics, 15 were significantly affected in one or both genotypes. The response of these 15 characteristics also appeared to have been caused by two effects; 10 of the 15 characteristics exhibited a common response to ploidy change over both genotypes while five traits showed a genotype-specific response to polyploidization. Tetraploid leaves also exhibited a darker leaf colour, which could be correlated to a higher pigment concentration. Furthermore, the results also show a decreased elongation rate and leaf size in tetraploids, which is suggested to be due to the observed lower cell density in the polyploid apple plants.