The morphology, chromosome number and nuclear DNA content of Tunisian populations of three Vicia species

Abstract

The aim of this work was to determine, for Tunisian populations (wild and cultivated) of Vicia sativa, V. villosa and V. narbonensis, whether differences in chromosome number, nuclear DNA content or morphology exist among the populations; in the case of V. sativa, with respect to a commercial cultivar from Spain and, in the case of V. villosa, with respect to two accessions from Aleppo (Syria). The idea was to identify variation that could be exploited for agronomic purposes. For the study, nine populations (3 per species) were compared regarding 12 morphological characters.The three species differed significantly with respect to the majority of the characters such as leaf area, node number, ramification, length of the most developed axis, leaf length, and the number of leaflets and inflorescences per plant. The comparison of these characters within each species revealed an intra-population polymorphism especially for V. sativa and V. narbonensis. For V. villosa, the three populations appeared homogeneous for the majority of studied phenotypical characters, independent of their origin. The polymorphism detected in the species seems to depend on altitude and pedo-climatic factors. All the studied populations were diploid, with 2n = 2x = 12 for V. sativa and 2n = 2x = 14 for V. villosa and V. narbonensis. The mean 2C DNA contents were 3.67 - 3.79 pg for V. sativa, and 12.83-13.17 pg for V. narbonensis: significant differences (P < 0.001) among the populations were observed only for V. villosa, the mean 2C nuclear amounts being 3.72 pg and 3.80 for the 2 Syrian populations and 4.17 pg for the population from Tunisia. The DNA content correlated significantly and negatively with the parameters related to the growth rate (number of branches and nodes at 10, 20 or 30 days after germination), indicating that some populations, of smaller genome size and faster growth, are adapted to sites having shorter growing seasons.   Key words: Vicia, Tunisia, morphology, nuclear DNA, populations, ploidy.