The question of independent axiomatizability has been studied widely in various classes of algebraic systems; in the present paper it will be studied in the context of quasi-varieties of groups.Let ~ be the class of all Abelian groups, ~ the lattice of the quasi-varieties in which all groups are soluble. It is a natural to ask for the existence of independent bases of quasi-identities of the quasi-varieties which are covers of the quasi-variety ~ in the lattice ~ . The present paper is devoted to the solution of this question.In the paper we shall find all covers of the quasi-variety ~ in the lattice ~9 " For each of these covers we solve the question of existence of an independent basis of quasiidentities.We note that for the cover ~V~p ~ Z ( p a prime number) of the quasi-variety the question of independent axiomatizability is solved only modulo Artin's conjecture about the infinity of the set of prime numbers modulo which p is a primitive root.We mention the following result of the paper.Let H be a finitely generated non-Abelian ~-group which does not contain non-Abelian nilpotent subgroups and such that the last nonidentity term in the derived series is torsionfree, then the quasi-variety ~V ~H possesses an independent basis of quasi-identities.At present, "few" quasi-varieties are known which are generated by a finitely generated group and do not have an independent basis of quasi-identities. The first example of this kind was given in [I, cf. also 2, 3, 4]. In connection with this the following result is of interest:THEOREM. The set of quasi-varieties each of which is generated by a 2-generator group and does not possess an independent basis of quasi-identities has the power of the continuum.The present paper may be considered as a continuation of [5].