Asymbiotic and Symbiotic Seed Germination of Anoectochilus Formosanus and Haemaria Discolor and Their F1 Hybrids

Abstract

Two orchid species Anoectochilus formosanus Hayata and Haemaria discolor var. dawsoniana, which have different flowering times in nature, were induced to flowering synchronously by controlling the culture temperature and light duration in the phytotrons. They were crossed, and the F1 hybrid seeds were collected and named as H. discolor × A. formosanus (HA) and A. formosanus × H. discolor (AH). It was found that fifty days after the asymbiotic culture in MS medium, the germination rates of all the four kinds of seed were higher than 70%. For the symbiotic seed germination on oatmeal agar (OMA) medium, only the R02, as compared to the R01 and R04 isolates of Rhizoctonia spp., had a more than 80% germination rate. SEM observation of various seed germination stages for the non-mycorrhizal and the mycorrhizal protocorms of A. formosanus showed that 70 days after seed sowing, the inoculated seeds developed to a more advanced stage than the non-inoculated control. Asymbiotic and symbiotic germination occurred after the uptake of water, and the seed coat was ruptured by the enlargement of embryo. Afterward the papilla, protocorm and apical meristem appeared. In the symbiotic germinated embryos, the fungal hyphae penetrated the protocorm and formed pelotons, which was the tolypophagy type of infection. No hypha infection was found in the asymbiotic germinated embryos.