Eustomabreeding, interspecific hybridization and cytogenetics

Abstract

The development of novel ornamental cultivars requires phenotypic and genetic variation. Interspecific hybridization is an important tool to achieve this variation. Eustoma grandiflorum (Raf.) Shinner, commonly known as lisianthus, has gained importance among ornamental crops, as cut-flower or potted plant, due to the shape of its flowers, which after several years of breeding resembles those of the rose; however, the color of lisianthus flowers ranges from white to purple, including greenish, rose and blue, and many forms with colored eyes, rings and brushes. The genus is endemic to America, and it distributes from the southern United States to Central America, including the Caribbean islands. E. grandiflorum is restricted to the southern United States and to northern Mexico. E. exaltatum (L.) Salisb. Ex G. Don distributes from central Mexico to Central America. Lisianthus breeding began around 50 years ago, and due to an indirect selection, many of the available cultivars nowadays, are susceptible to high temperatures, and if the plantlets are exposed to temperatures above 25°C they might rosette. In this respect, in order to achieve genetic variation and produce heat tolerant Eustoma cultivars, we conducted a breeding program, which includes interspecific hybridization among E. grandiflorum and E. exaltatum, the last being found in its natural habitat at an average temperature above 25°C during summer. Many crosses were performed in both directions, and F1, BC1 and S1 generations were achieved, showing outstanding ornamental traits, such as different color patterns, stem and flower size and heat tolerance. Furthermore, chromosome counts and chromosome identification were possible through in situ hybridization of rDNA and retrotransposon probes to metaphasic chromosomes in both species.