Endoreduplication level affects flower size and development by increasing cell size in Phalaenopsis and Doritaenopsis

Abstract

Endoreduplication is an alternative form of the cell cycle that is common in approximately 90 % of angiosperm species. Endoreduplication, determined using flow cytometry, occurs in various tissues of Phalaenopsis and Doritaenopsis species belonging to the Phalaenopsis (Phal.) alliance. In this study, flowers and leaves of nine cultivars from the small, middle, and large flower groups of the Phal. alliance were used to investigate the relationship between endoreduplication level and flower size. Some degree of endoreduplication was detected in all cultivars. A higher level of endoreduplication (2C–16C) was observed in cultivars from the large flower group than in those from the middle and small flower groups (2C–8C). In the leaves, endoreduplication tended to be found in middle and large flower group cultivars, but it varied with the cultivar rather than the flower group. Different patterns of endoreduplication were recorded at various stages of flower development in the Phal. hybrids ‘Queen Beer’ (small flower group) and ‘KV01’ (large flower group). Endoreduplication during flower development caused an increase in ploidy levels from 2C–4C to 2C–8C in ‘Queen Beer’, and from 2C–8C to 2C–16C in ‘KV01’; thus higher ploidy levels were detected in cultivars from the large flower group. Endoreduplication levels affected flower size and development by increasing cell size, indicating a positive relationship between endoreduplication and petal size in the Phal. alliance. Controlling flower size via the adjustment of the level of endoreduplication should be considered in breeding programs aimed at developing new cultivars.