No loss of genetic diversity in small and isolated populations of Medicago sativa subsp. falcata

Molecular allozyme markers of three polymorphic isozymes were used to estimate the genetic diversity among the seed progeny in fragmented Estonian populations of sickle medic Medicago sativa ssp. falcata L. depending on the population size and the isolation degree. Genetic diversity He was high in all populations, ranging between 0.795 and 0.893. No correlation between the genetic diversity measures and population size or isolation distance was found. Even the smallest population had equally high genetic diversity as about a hundred times larger population. Genetic differentiation of populations into two major groups was associated with the geographic position of populations, except one remote population. Elimination of seed progeny of reduced fitness by embryo abortion and continuous yearlong contribution of the highly heterozygous progeny through the soil seed bank are considered as important supplementary factors that have contributed to maintaining high levels of genetic diversity in populations of sickle medic in addition to its autotetraploid nature and perennial life form.