The Effect of Indigenous Root-Nodulating Bacteria on Nodulation and Growth of Faba Bean (Vicia Faba) in the Low-Input Agricultural Systems of Tigray Highlands, Northern Ethiopia

Abstract

This study was initiated to isolate and characterize indigenous rhizobia nodulating faba bean, and evaluate symbiotic characteristics between the crop and the rhizobia in major faba bean producing areas in Tigray highlands. Field crops were also surveyed for nodulation in selected sites of seven (7) faba bean growing districts. A total of 44 rhizobial strains were isolated and their symbiotic properties (nodule number, fresh weight, color and plant growth) were recorded. A total of 12 strains with good symbiotic properties were characterized for their morphological and physiological traits on Yeast Extract Manitol Agar (YMA) medium. The result of the study showed the presence of diversity in morphological, physiological and symbiotic properties among the rhizobial strains. There was statistically significant difference in nodule number, fresh weight and shoot height (p< 0.05) and great variation in nodule color within and among the districts. Nodulation status of the field crops was poor except Ofla, D/Temben and Alaje districts. Though the presence of diversity among the strains revealed the possibility of getting potentially effective adaptable rhizobial strains that enhance faba bean productivity, the weak symbiotic properties observed during isolation and nodulation status survey might partly be responsible for yield variation and reduction in low input cropping systems of Tigray. Hence, studies on a need for inoculation and factors responsible for poor nodulation need to be undertaken to realize the role of biological nitrogen fixation in Tigray cropping systems.

Key words: Biological nitrogen fixation, Faba bean, Nodulation, Rhizobia, Symbiotic Effectiveness, Tigray.