Petrocosmea grandiflora Hemsl. (Gesneriaceae) is a perennial herb endemic to China with large and beautiful bluish violet flowers of potential horticultural value. The first specimen of this species was collected in 1893 by British botanist Hancock in Mengzi County, Yunnan Province, and it was described by Hemsley in 1895, with the type specimen deposited at the Herbarium of the Royal Botanic Gardens, Kew, UK. For 121 years the species remained unseen until it was rediscovered in the wild in 2016. However, despite multiple field explorations only three populations have so far been found in the wild, with < 1,000 individuals in total. Petrocosmea grandiflora has been categorized as a Yunnan Key Protected Wild Plant, as a Plant Species with Extremely Small Populations in Yunnan Province, and as a Threatened Species of Higher Plants in China, and it should be categorized as Critically Endangered according to the IUCN Red List assessment criteria.

During September 2022–December 2023, with the support of a conservation programme (2021SJ14X-06) of Yunnan Forestry and Grassland Bureau, we successfully established an in vitro regeneration protocol using direct somatic embryogenesis and shoot organogenesis from leaf explants of P. grandiflora. The explants were surface sterilized and inoculated on induction media. After 8 weeks, the regeneration rate of adventitious shoots was 98%, and the induction rate of somatic embryos was 53%. Three months after transplanting rooted plantlets, the survival rate was > 90%.

(a) Petrocosmea grandiflora flowering in the wild; (b) adventitious shoot formation induced from one leaf explant; (c) somatic embryogenesis from one leaf explant; (d) seedlings growing on medium; (e) regenerated plantlets 3 months after transplanting.

The successful regeneration of P. grandiflora using plant tissue culture opens up possibilities for restoring wild populations, although protection of the three known populations is also required. We plan to model the future trend of these populations to guide conservation efforts, and to use P. grandiflora as a germplasm source to study and cultivate new flower varieties for social and economic benefits.