Development of symbiotic interactions in the faba bean (Vicia faba L.) roots
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Double-inoculation of faba bean (Vicia faba L.) seeds before sowing with rhizobium bacteria and mycorrhizal fungi is a known agronomic practice. It improves symbiotic nitrogen fixation and enhances legume supply with mineral elements and water. Effective symbiosis makes it possible to replace some of the required mineral fertilizer needed for plant growth with symbiotically fixed. This will ensure more environmentally friendly agricultural production. The formation of an effective symbiosis depends on a number of biotic and abiotic factors affecting the biochemical signals released by the partners. The biochemical mediator for symbiosis formation is flavonoids. The aim of this experiment was to test the effects of rhizobial and mycorrhizal inocula on symbiosis formation under different temperatures. Beans are an important source of protein for animal feed and human consumption. Four cultivars of faba beans were used - two V. faba var. minor Beck. -‘Fuego’ and ‘Lielplatone’, and two V. faba var. major Harz. - ‘Bartek’ and ‘Karmazyn’. The combination of microorganisms for seed inoculation influenced the frequency of root mycorrhization and abundance of arbuscules. The content of flavonoids in seed exudates correlated (r = 0.93) with germination temperatures. The use of mycorrhizal fungi alone or in combination with rhizobia reduced the amount of flavonoids in the bean seed exudate. In the pot experiment the amount and size of nodules significantly differed between cultivars. Use of mycorrhizal preparation mitigated the effect of inadequate germination temperature. Higher degree of mycorrhization and more intense formation of arbusculs formation was observed in the bean roots grown in vegetation pots in comparison with field ones. Local bred ‘Lielplatone’ had significantly better compatibility with microsymbionts in local agroclimatic conditions.