Double Mutant Analysis of Sequential Functioning of Pea (Pisum sativum L.) Genes: Sym13, Sym33 and Sym40 During Symbiotic Nodule Development

Two double mutants carrying pea symbiotic gene pairs sym13, sym40 and sym33, sym40, respectively, were constructed using single mutants blocked at different nodule developmental stages: E135f (sym13), SGEFix–‑1 (sym40) and SGEFix–‑2 (sym33). The epistasis of the mutant allele sym40 over the mutant allele sym13 and sym33 over sym40 was shown with respect to nodule histological and ultrastructural organisation. Thus, the proposed earlier sequential functioning of genes during infection process: Sym33→Sym40→Sym13 has been confirmed