A DNA cytophotometric study of salt adaptation in Allium cepa

Abstract Nuclear DNA was measured by Feulgen cytophotometry in NaCl-exposed Allium cepa roots and Nico-tiana bigelovii calli cultured in vitro. Analysis of the differentiation zone of A. cepa roots grown in water showed that only 2.8% of the nuclei had DNA contents higher than 4 C, where 2 C nuclei were predominant. In roots grown in salt water, 2 C nuclei were less numerous than 4 C nuclei and the DNA content was greater than 4 C in 19.2% of the cells, with 1.4% of the cells having a DNA content of 16 C. Two C, 4 C, 8 C, and a few 16 C nuclei, together with many nuclei with intermediate DNA content values, occurred in both the control and salt-treated calli of N. bigelovii. About 49.1% of the nuclei had DNA values around 2 C in the controls, while the percentage of cells with nuclei with higher DNA content values increased in calli as the NaCl concentration in the medium increased. Fifteen per cent of the nuclei had DNA values around 16 C in calli grown on media with 10 gr l−1 NaCl added, compared to 2.8..

Microsatellite markers are powerful tools for discriminating among olive cultivars and assigning them to geographically defined populations

Twelve simple sequence repeat (SSR) loci were used to differentiate among 118 cultivars sampled in several countries of the Mediterranean basin and to analyze the genetic structure of olive cultivar gene pools. The markers were found to have high discrimination power. On average, with a single assay it was possible to discriminate 96% of the pairwise comparisons and, with a combination of 3 loci, virtually all cultivars were distinguished. The SSR markers were also tested for their ability to assign cultivars to their geographic population of origin. A selection of 6 loci was found to maximize assignment accuracy, correctly reallocating up to 75.4% of cultivars to their population of origin. Because of the confusion surrounding the origin of most olive cultivars, their molecular identification and ascertainment of origin will be extremely useful for germplasm management and breeding