Metodologie per l’ottenimento di ibridi interspecifici di Lilium spp. e per la verifica dello stato ibrido delle progenie
Author(s)
Nesi, Beatrice
Date Issued
April 22, 2008
Type
Doctoral Thesis
Abstract
The importance of Lilium for cut flowers production has been increased over the last 30 years thanks to the progress in genetic improvement, allowing to put on the market new hybrids of high commercial interest. Among the bulbous plants, Lilium is the most important species from an economic point of view and, thanks to the continuous work of hybridisation, several hundreds cultivars are grown today. Generally they belong to three commercial groups: 70% is represented by the “Asiatic hybrids” group; 20% by the “Oriental hybrids” group and 10% by the “Longiflorum hybrids” group. Recently a fourth group has started to be considered, the LA group, interspecific hybrids between ‘Longiflorum’ and ‘Asiatic’. In breeding programmes for ornamental bulbs, interspecific hybridisation is one of the most important ways to introduce new genetic variations, although this may be restricted because of incompatibility. The genus Lilium generally includes allogamous species that because of self incompatibility problems are not able to produce seeds when they are self pollinated. The intraspecific crosses produce a large quantity of seeds, whereas crosses among different species create many problems caused by sexual barriers that hamper interspecific hybridisation, and that can be distinguished between pre-fertilization and post-fertilisation barriers. Pre-fertilisation barriers are due to the impossibility of pollen tube to cross the stylus, to incompatibility between the stylus and the pollen itself, and to ovary abortion. The post-fertilization barriers are due to the degeneration of the endosperm in the developing embryo.
A breeding programme on lily was carried out at the CRA-VIV, former ISFlor, with the aim to obtain new Lilium hybrids with high commercial traits, as colour, shape and flowers size.
The goal of this research was to develope some methods to obtain new interspecific hybrids of Lilium overcoming the sexual barriers that occur among parental and to verify their hybrid condition. Ovary and ovule culture have been applied to produce interspecific Lilium hybrids. Several crosses among Asiatic hybrids (‘Golf’, ‘Polyanna’ and ‘Gironde’), Oriental hybrids (‘Lombardia’), and Longiflorum hybrids (‘White Haeven’ and ‘White Magic’) were made using just breaking flower buds and cut-style-method. Other crosses were carried out using clones previously selected at the CRA-VIV for several flower traits like colour, shape and pollen absence. Several wild species like L. pumilum, L. regale, L. aurelian, L. leucanthum and L. New Zealand were included. Seven, fourteen and twenty - one DAP (Days After Pollination) ovaries were cut and cultivated ‘in vitro’ using 4 different substrates (MSO, LO1, IAA0.5 and NAA1) for 50 and 60 days. Subsequently the most swollen ovules were taken out from ovary and subcultivated on two substrates, IBA0,5, and NAA0,1. In some cases, after 180 days an embryo developed.
Random amplified polymorphic DNA (RAPD) markers were used for early identification of interspecific hybrids. RAPD profiles obtained using 39 primers on 3 different types of cross combinations (LA, AO and LO), have highlighted differences between parentals, many homogeneous bands between hybrids and female parents and some bands in common only between hybrids and male parents. These last bands have confirmed an occurred fertilization and the hybrid condition of the progenies.
Additional information
Dottorato di ricerca in Ortoflorofrutticoltura
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