Breeding of lilies and tulips-Interspecific hybridization and genetic background

Abstract

Lilies and tulips (Liliaceae family) are economically very important ornamental bulbous plants. Here, we summarize major breeding goals, the role of an integrated method of cut-style pollination and fertilization followed by embryo rescue and mitotic and meiotic polyploidization involved in new assortment development. Both crops have been subjected to extensive interspecific hybridization followed by selection. Additionally, spontaneous polyploidization has played a role in their evolution. In lilies, there is a tendency to replace diploids with polyploid cultivars, whereas in tulip a majority of the cultivars that exist today are still diploid except for triploid Darwin hybrid tulips. The introduction of molecular cytogenetic techniques such as genomic in situ hybridization (GISH) permitted the detailed studies of genome composition in lily and tulip interspecific hybrids and to follow the chromosome inheritance in interspecific crosses. In addition, this review presents the latest information on phylogenetic relationship in lily and tulip and recent developments in molecular mapping using different DNA molecular techniques.

Keywords: GISH; Lilium; Phylogeny; Tulipa; chromosome; interspecific hybridization.

Fig. 1

Interspecific crosses of Lilium species cited with modification from Asano (1987). ○, hybrids easily obtained in normal crossing; △, hybrids obtained in normal crossing followed by embryo rescue; (△), hybrids obtained by cut-style pollination followed by embryo rescue; × and (×), no hybrid obtained in normal crossing and cut-style pollination, respectively.

Fig. 2

Interspecific hybrids and their parent. (A) L. longiflorum, (C) L. Asiatic Hybrids ‘Connecticut King’, (B) their hybrid, (D) a Longflorum hybrid ‘Rote horn’ derived from the cross between L. longflorum and L. Asiatic Hybrids ‘Utagoe’, with a perfect trumpet shaped flower due to asymmetrical genome composition, (E) a hybrid of L. × formolongi × an Asiatic Hybrid, with a well-balanced flower shape as well.

Fig. 3

Schematic diagram of indeterminate meiotic restitution (IMR) in microsporogeneis in interspecific hybrid lilies. For clarity only three pairs of homoeologous chromosomes of the respective species (back and gray) and an example of the chromosome assortment are shown.

Fig. 4

Genome composition of an amphydiploid derived from crossing L. formolongi ‘Augusta’ (LL) with 2n gamete of L. Asiatic Hybrids ‘Regata’ (AA). Genomic in situ hybridization to somatic metaphase chromosome complement shows 24 chromosomes of L genome (green fluorescence) and 24 chromosomes of A genome (blue DAPI fluorescence), indicating that ‘Augusta’ provided spontaneous 2n female gamete. Bar = 10 μm.

Fig. 5

Interspecific crosses of Tulipa species cited with modification from Hagiya (1971). ^a Cultivar classification according to Classified list and international register of tulip names (1958); SE, Single Early; M, Mendel; T, Triumph; D, Darwin; B, Breeder; C, Cottage; L, Lily-flowered; P, Parrot; F, Fosteriana; K, Kaufmanniana; G, Greigii. ^b ◎, several successful attempts, effectivity high (compatible); ○, one successful attempt, effectivity high; △, several successful attempts, effectivity low; ×, no seed obtained; –, not determined.

Fig. 6

Bulblet formation via culture in ovules and embryos excised after 7 weeks after pollination of the intraspecific cross of T. gesneriana; ‘Christmas Dream’ × ‘Ile de France’. (A) a bulblet via ovule culture, (B) and (C) bulblets via germinative and adventitious growth in embryo culture, respectively.

Fig. 7

Discrimination of chromosomes originating from T. gesneriana (G) and T. fosteriana (F) in the genomes of ‘Kikomachi’ (2n = 2x = 24). (A) Genomic in situ hybridization to somatic metaphase chromosome complement showing 18 chromosomes of G (green fluorescence) and 6 F chromosomes (red fluorescence). Recombinant chromosome is defined as F/G indicating a T. fosteriana centromere with T. gesneriana chromosome segment. (B) A diagrammatic representation of chromosomes in ‘Kikomachi’ (2n = 2x = 24). In this figure, the black color represents the T. fosteriana genome, while white represents T. gesneriana one.