S05 - Session P3 - Cytogenetic analysis for ploidy level determination of phalaenopsis cultivars in Korea

Authors: Samantha Sevilleno *, Hye Ryun An, Ki Byung Lim, Yoon Jung Hwang

Phalaenopsi s is one of the most popular cultivated orchids worldwide due to its attractive and long-lasting flowers. Interspecific and intergeneric hybridization have been used to produce novel cultivars in Phalaenopsis orchids. Their basic chromosome number is n = 19, and previous studies have shown a diverse number of chromosomes, implying the frequent occurrence of polyploidy which may cause a disturbance during meiosis of interspecific hybrids. Despite of the cytogenetic data available for Phalaenopsis species, limited information is known on the significant breeding stocks of Phalaenopsis cultivars, which is crucial in formulating systematic breeding programs. In this study, cytogenetic analysis in Phalaenopsis cultivars was conducted to determine their ploidy level as well as their genetic characteristics and variations. Somatic metaphase chromosome spreads were prepared from young roots of twenty cultivars. Results have shown a variation in chromosome numbers. P. 'Snow Angel' and P. 'Snow Dream' were observed to be triploid cultivars (2n=3x=57), while a few cultivars were true tetraploid (2n=4x=76) such as the P. 'Joyful', P. 'K7', P. ' Beauty Queen', P. ' Purple Queen' and P. 'Pink Marble'. One cultivar, P. 'Little Mary', was a hypotriploid (2n=3x-1=56). Several cultivars were hypotetraploid, such as P. 'Santiago' and P. 'Santos (2n=4x-5=71); P. 'Orange Dream' and P. 'Pink Lady' (2n=4x-4=72); and P. 'Aria' and P. 'Taida Salu x Rueylih Stripe (2n=4x-1=75). Hypertetraploid chromosome numbers were observed in P. 'SM5116', P. 'Valentino' and P. 'V8' (2n=4x+1=77); and P. ' Pinky', P. 'Little Prince', and P. 'Tiny Bell' (2n=4x+2=78). These findings on the chromosome numbers of selected Phalaenopsis cultivars will provide fundamental knowledge to orchid breeders in relation to selecting the right variety for cultivation.