Chromosome studies and the implications on ornamental characteristics in Passiflora mooreana (Passifloraceae)

The genus Passiflora (Passifloraceae) comprises more than 500 species and is an important genetic resource for horticulture. Among Argentinian native species, P. mooreana have phenotypic characteristics to make it a candidate to participate in the breeding program carried out in the Instituto de Floricultura, (Institute of Floriculture, National Institute of Agronomic Technology, Argentina). The purpose of this program is to develop, by interspecific crosses, new attractive and cold tolerant varieties. The aim of this work was to investigate the chromosome numbers of P. mooreana and to make a morphological characterization of ornamental features in Formosa and Corrientes genotypes. The chromosome number of P. mooreana which is important has not been previously investigated. Comparative measures of the width and length of the leaves and the flower diameter show statistical differences between the two genotypes and were higher in the one from Corrientes. No differences were found between the genotypes in the crown diameter and width of the petals. In the flow cytometric analysis, the Corrientes genotype shows twice the value of the Formosa genotype. The chromosomal number was 2n=2x=18 (Formosa) and 2n=4x=36 (Corrientes). This characteristic provides to the Formosa genotype with higher probabilities of a successful cross with species from the same subgenus because they have the same chromosome number. The tetraploid genotype would have best chances to be crossed with tetraploid species or artificially polyploidized hybrids. Both genotypes showed a percentage of pollen viability enough to be considered as a male parent in crossings.