Flow cytometric analysis of genome size variation in some Passiflora species

Nuclear genome size variation was studied in eight taxa of Passiflora. Nuclear DNA content was estimated by flow cytometry of nuclei stained by propidium iodide. 2C DNA content ranged from 3.16-5.36 pg for diploids and 1.83 pg for tetraploid. Differences in nuclear genome size were observed among Passiflora species (pg): P. suberosa 1.83, P. edulis f. edulis 3.16, P. edulis f. flavicarpa (Brazil) 3.19, P. edulis f. flavicarpa (Mexico) 3.21, P. mucronata 3.40, Passiflora edmundoi 3.43, P. laurifolia 3.88, P. giberti 3.92, P. quadrangularis 5.36, the largest value being up to 192% greater than the smallest. The means of 2C DNA content were compared by the Tukey test, and the differences in genome size permitted the recognition of five taxa groups. The result was the same for the means 2C genome size (Mbp) values. The genetic parameters were studied with their respective estimators, phenotypic variance (sigma2F), genotypic variability (PhiG), and the genotypic determination index (H2). The genotypic determination index presented high magnitude estimates (greater than 99%) emphasizing the reliability of the results and demonstrating the efficiency of determining the DNA content in the species using only one leaf per plant. Passiflora species show great phenotypic variability and have different geographic distribution that might implicate in genetic diversity.