BREEDING BARRIERS IN RED PHALAENOPSIS ORCHIDS

Breeding barriers in producing hybrids by intergeneric, inter- and intra- specific hybridization in Phalaenopsis have been observed. In this study, four cultivars of red Phalaenopsis which are known to be difficult in hybridization, including Doritaenopsis Ever Spring Prince ‘#1’ (ESP), Dtps. Queen Beer ‘KHM 159’ (QB), Dtps. Taida Salu ‘KHM 101’ (TS), and Phalaenopsis Brother Girl ‘B’ (BG) were investigated for the mechanisms underlying the crossing barriers. Root tip squash observation showed that all of these selected cultivars are triploids with 2n = 3x = 57 chromosomes. To test their crossing behaviors, these four cultivars were either self- crossed, or used as the pollen and pistillate parents in reciprocal crossing with three cultivars with normal behavior in crossing, including Phal. Brother Irene ‘Feng Fong’, Phal. Sogo Yukidian ‘V3’, and Phal. Tai Lin Redangel ‘V31’. These normal cultivars are tetraploids with 2n = 4x = 76 chromosomes. The crossing results showed that the closure of stigma cavities occurred in TS and BG, while such stigma closure was never observed when QB or ESP was used as the pollen parent in crosses. However, hybrid progenies were obtained only from the crosses between ESP or TS (pistillate parent) with the normal cultivars. Taken together, these results suggest that crossing difficulties in these four selected cultivars may be caused by odd chromosome set and some other factors of male or female parents.