Comparison of the morphology, growth and development of diploid and autotetraploid 'Hanfu' apple trees

- It reports relevant morphological and biological characteristics associated with growth and development in diploid and autotetraploid apple.
- The autotetraploid apple plants exhibited significant characteristics of polyploidy.
- The autotetraploid plants delayed flowering until 5 years of age, which was 2 years older than the age at which the diploids first flowered.

Artificial induction of polyploidy is an efficient technique for improving the biological properties and developing new varieties of many plants. Autotetraploid plants were generated through in vitro chromosome doubling of the 'Hanfu' apple cultivar (Malus × domestica) using colchicine treatment. In the present study, we analysed and compared the differences in the morphological and biological characteristics of diploid and autotetraploid 'Hanfu' apple cultivars from 2009 to 2014. We found that the autotetraploid plants flowered at 5 years of age, which was 2 years later than in the diploid plants. Compared with the diploid plants, the autotetraploid plants showed retarded growth and significant dwarfing characteristics before flowering, but their growth was restored after flowering. The stomata were larger and the leaves were not only larger and heavier but also darker green in the autotetraploid than in the diploid plants. The chlorophyll content of the leaves was significantly higher and the photosynthetic efficiency and fluorescence performance were increased in the autotetraploid plants. Additionally, the volume and size of the flowers, fruits and seeds were greater and the soluble solid contents were higher in the autotetraploid than its diploid counterparts. In this study, we provide the first detailed analysis of the morphological and biological characteristics associated with growth and development in diploid and autotetraploid 'Hanfu' apple, and the results will make a meaningful contribution to the breeding of polyploid apples.