Symbiogenetics and breeding of a macrosymbiont for increased nitrogen fixation capacity with special reference to the pea (Pisum sativum L.)

Abstract

This article presents the results of long-term experimental studies on symbiogenetics and breeding of macrosymbionts in a system of legume-rhizobial symbiosis with the pea (Pisum sativum L.) as an example. The collection of pea symbiotic mutants was created and genetically studied. The new symbiotic genes were identified and localized on a Pisum chromosome map. The dominant symbiotic mutants characterized by high productivity and active nitrogen fixation were induced in the pea for the first time. Certain physiological peculiarities of the auxin and gibberellin phytohormone content were studied in symbiotic mutants. The differences in the activity of nitrogen fixation during ontogeny were revealed for numerous mutants. The forms with a prolonged period of active nitrogen fixation were isolated. A new approach to estimate the efficiency of legume-rhizobial symbiosis was proposed. The method of use of symbiotic mutants in breeding for higher efficiency of nitrogen fixation was proposed for the first time. This method is based on the interaction between different sym genes within one genotype. A series of productive constant recurrent lines of the seventh generation was designed which exceed commercial pea cultivars in nodulation and nitrogen fixation activity. Lines are characterized by accumulation of higher root biomass with increased nitrogen content in them. This approach allows their use in agricultural production instead of expensive organic and mineral fertilizers.