Flow cytometric measurement of nuclear DNA content in Capsicum (Solanaceae)

Nuclei were isolated from leaf tissue of different Capsicum species and the relative fluorescence intensity was measured by flow cytometry after propidium iodide staining. Pisum sativum nuclei with known nuclear genome size (9.07 pg) were used as internal standard to determine nuclear DNA content of the samples in absolute units. The 2C DNA contents ranged between 7.65 pg in C. annuum and 9.72 pg in C. pubescens, and the general mean of the genus was 8.42 pg. These values correspond, respectively, to 1C genome size of 3,691 (C. annuum), 4,690 (C. pubescens) and 4,063 (general mean) Mbp. In general, white-flowered species proved to have less DNA, with the exception of C. praetermissum, which displayed a 2C DNA content of 9.23 pg. It was possible to divide the studied species into three main groups according to their DNA content, and demonstrate differences in DNA content within two of the three species complexes established on the basis of morphological traits.