XXIIIrd International Eucarpia symposium, Section Ornamentals ...

NEW GENOTYPES OF HIBISCUS ROSA-
SINENSIS THROUGH CLASSICAL BREEDING
AND GENETIC TRANSFORMATION
Hibiscus is the largest genus of the mallow family (Malvaceae), a group comprising 116
genera, many of which are economically valuable. Several Hibiscus species are used all
over the world as ornamental plants. The most popular one, H. rosa-sinensis shows a
high variety of flower colours and shape. However, its use as an ornamental plant is
currently restricted by a few constraints: 1) most of the commercialised pot-plant
varieties are obtained by applying growth retardants; 2) the range of colours and types in
use is limited if compared with the available ones; 3) the present cultivars are not fit for
the Mediterranean region in terms of propagation and growth rates, as well as flowering;
4) the market requires frequent introductions of novelties.
In 2006, a breeding programme was established at CRA-FSO with the aim of
selecting specific cultivars suitable for pot-plant production and creating new genotypes
well-adapted to the Mediterranean climate. A partial diallelic cross design (reciprocals
without self-fecundations) was used to test the ability of the collected cultivars to produce
valuable progenies. Only a limited number of cross progenies resulted to combine
desirable characters with a reasonable degree of fertility. A range of very good female
parents able to produce seeds in all cross combinations was found. The first selected
cultivars are presented.
At the same time, another approach was followed, in order to investigate whether
desirable morphological modifications (plant size reduction for pot plant cultivation) could
be obtained by transforming H. rosa sinensis with Agrobacterium rhizogenes. In vitro
seedlings were used as sources of explants for the transformation experiments. Two A.
rhizogenes strains (ATCC 15834 and NCPPB 1855) were employed. Axenic hairy root
cultures were established about 4 months after inoculation. Hairy roots grew vigorously
on hormone-free medium whereas normal roots did not. Transformed roots displayed a
typical hairy root phenotype characterized by fast growth, high lateral branching and lack
of geotropism. So far, after more than one year of cultivation, a clone of hairy root
deriving from a cotyledon formed a friable yellowish callus at root node level; several
adventitious buds are spontaneously regenerating from it. Work is still in progress.
LP13
Luca Braglia
Antonio Mercuri
Laura De Benedetti
Marco Ballardini
Cesare Bianchini
CRA-FSO Research Unit
for Floriculture and
Ornamental plants, Corso
degli Inglesi 508, 18038
Sanremo – ITALY
a.mercuri@istflori.it
antonio.mercuri@entecra.it
Session Short presentations 57