ABSTRACT
BACKGROUND AND AIMS: The heterocarpic species Atriplex tatarica produces two types of seeds. In this study, how basic population genetic parameters correlate with seed germinability under various experimental conditions was tested. METHODS: Population genetic diversity was ascertained in eight populations of A. tatarica by assessing patterns of variation at nine allozyme loci. Germinability of both seed types from all sampled populations was determined by a common laboratory experiment under different salinity levels. Basic population genetic parameters, i.e. percentage of polymorphic loci, average number of alleles per locus and observed heterozygosity were correlated with observed population germination characteristics. KEY RESULTS: Atriplex tatarica possesses a remarkable heterocarpy, i.e. one type of seed is non-dormant and the other shows different dormancy levels in relation to experimental conditions. Significant negative correlations have been detected between germination of both seed types and the coefficient of inbreeding, and a significant negative correlation between germination of dormant seeds and other population genetic parameters, i.e. percentage of polymorphic loci and average number of alleles per polymorphic locus. Moreover, populations from the region characterized by a shorter growing season manifested higher germinability, i.e. had lower dormancy, than those from the lower-latitude one. CONCLUSIONS: In general, germination of non-dormant seeds is probably not under strong genetic control. Hence, they germinate as soon as conditions are favourable, thus ensuring survival in the short term, but populations risk local extinction if conditions become adverse (i.e. a high-risk strategy). In contrast, germination of the dormant type of seeds is under stronger genetic control and is significantly correlated with basic population genetic parameters. These seeds ensure long-term reproduction and survival in the field by protracted germination, albeit in low quantities (i.e. A. tatarica also adopts a low-risk strategy).
Subject(s)
Amaranthaceae/genetics , Germination , Alleles , Amaranthaceae/embryology , Genes, Plant , Genetics, Population , Heterozygote , Seeds/physiologyABSTRACT
Seed oil of wild Amaranthus caudatus from Ecuador was analyzed for determining the tocopherol, fatty acid, and sterol contents. The data obtained were compared with the analogous chemical profile of seed oil of Italian A. caudatus with the objective of evaluating the nutraceutical and alimentary potential of the Ecuadorian matrix. Supercritical fluid and ultrasound-enhanced extractions were performed on both matrices. Qualitative and quantitative determinations of tocopherols were performed by HPLC, whereas GC and GC-MS were used to determine the fatty acid composition and sterols, respectively. Supercritical fluid extraction at 400 atm was the most efficient extraction method in terms of both total yield extract and tocopherol yield. Seeds of Ecuadorian of A. caudatus contained higher levels of tocopherols than Italian samples, whereas the fatty acid composition and sterol content were similar. From the obtained results it can be suggested that seed oil of wild Ecuadorian A. caudatus can prove to be an effective nutraceutical and alimentary resource and a valid alternative to the European varieties.
