African violet (Saintpaulia ionantha H. Wendl.): classical breeding and progress in the application of biotechnological techniques

Abstract

As a result of its domestication, breeding and subsequent commercialization, African violet (Saintpaulia ionantha H. Wendl.) has become the most famous and popular Saintpaulia species. There is interest in producing cultivars that have increased resistance to pests and low temperature, in the introduction of novel horticultural characteristics such as leaf shape, flower colour, size and form, and in improved productivity and enhanced flower duration in planta. In African violet, techniques such as the application of chemical mutagens (ethylmethanesulfonate, N-nitroso-N-methylurea), radiation (gamma (γ)-rays, X-rays, carbon ion beams) and colchicine have been successfully applied to induce mutants. Among these techniques, γ radiation and colchicine have been the most commonly applied mutagens. This review offers a short synthesis of the advances made in African violet breeding, including studies on mutation and somaclonal variation caused by physical and chemical factors, as well as transgenic strategies using Agrobacterium-mediated transformation and particle bombardment. In African violet, Agrobacterium-mediated transformation is affected by the Agrobacterium strain, selection marker, and cutting-induced wounding stress. Somaclonal variation, which arises in tissue cultures, can be problematic in maintaining true-to-type clonal material, but may be a useful tool for obtaining variation in flower colour. The only transgenic African violet plants generated to date with horticulturally useful traits are tolerant to boron (heavy metal) stress, or bear a glucanase-chitinase gene.

The first genome for the Cape Primrose Streptocarpus rexii (Gesneriaceae), a model plant for studying meristem‐driven shoot diversity

“…In addition, several methodologies have been successfully applied to investigate gene function in Streptocarpus . Most of this work has been carried out on the ornamental Streptocarpus ionanthus (formerly Saintpaulia ionantha , African Violet) for breeding purposes: here, agrobacterium‐mediated transformation was successful (Kushikawa et al, 2001 ), as well as chemical mutagenesis with ethylmethanesulfonate, colchicine, and physical mutagenesis through exposure to different types of irradiation (da Silva et al, 2017 ). In S. rexii , a successful virus‐induced gene‐silencing protocol was recently reported (Nishii et al, 2020 ).…”

Genetic engineering of novel yellow color african violet (Saintpaulia ionantha) produced by accumulation of Aureusidin 6-O-glucoside

“…Wendl. ; Gesneriaceae) is a commercial ornamental plant that can be easily propagated [7]. African violet has more than 22 species and 2000 cultivars with diverse petal color, floral shape, and color range of white, red, purple, and pink [8].…”

“…The Saintpaulia 'Jolly Diamond' cultivar has white petals; the number of petals is much more than its flowers and the petals hang slightly as they grow inwards [9]. Despite the variety of colors available among African violets, however, yellow has not yet been observed in this species [5,7].…”

“…In transformed Ipomoea nil petals, the co-expression of the 4'CGT and AS1 genes induced expression of AOG and intensified the pale yellow color of the primary petals to visible yellow [19]. Genetically engineered production of yellow petals in important ornamental plants such as Geranium, Lathyrus odoratus, Cyclamen and Saintpaulia has not been reported [7,19].…”