Field performance of vegetative form traits of neopolyploids produced by in vitro colchicine treatment in Pyrus communis

• Phenotypic traits performances of somatic chromosome doubling neopolyploids growing in greenhouse and in the field were examined.
• Neopolyploids showed a wide range of variation in vegetative traits.
• All neopolyploids had shorter plant height than their diploid control.
• Neopolyploid generally had thicker leaf lamina than their diploid control.

The induction of polyploidy to improve agronomically and economically useful characters is a process commonly used in crop plants. Neopolyploids were obtained from the diploid pear cultivar ‘Fertility’ by in vitro colchicine treatment. Different clones of polyploids were rooted to be transferred to the greenhouse and then to the net house, a survey orchard was established. The morphological characteristics and the performance of 3 tetraploid clones, 2 triploid clones, 1 mixploid clone and a diploid control were investigated under greenhouse and field conditions. Results revealed that plants of different neopolyploids showed markedly different phenotypic traits. Compared to the diploid control, three out of four polyploid clones plants had significantly thicker leaves and a shorter petiole length. The significance of the difference in leaf index (ratio of leaf lamina length to leaf lamina width) between diploid and polyploids depended on the individual clone of the neopolyploid plants. In the greenhouse and the field, the triploid clone ‘3x − 1’ and the tetraploid clones ‘4x − 1’ and ‘4x − 2’ had significantly decreased leaf index, and the triploid ‘3x − 2’ had significantly increased leaf index. However, the tetraploid clone ‘4x − 4’ and the mixploid clone ‘Mix − 1” showed phenotypic abnormalities, such as stunted growth and leaf malformation. The ex vivo grafted shoots of the pentaploid ‘5x − 1’ and ‘5x − 2’ were very difficult to maintain or had a very short survival period. The grafted plants of triploid ‘3x − 2’ showed a compact habit. Most neopolyploid plants had significantly shorter internodes and all had reduced plant height compared to the height of their parent diploid plants.