Effect of legume extracts on root rot pathogens and germination of common bean (Phaseolus vulgaris)

Application of undecomposed green manure have been reported to result in poor germination and crop establishment thus poor yields. To understand the mechanism through which low emergence occurs, various legume extracts from lablab, soybean, beans and groundnut were tested common bean germination and root rot pathogens by evaluating the extracts on germination of bean seed, mycelial growth, and spore germination. Observations were made on bean germination percentage, shoot length, dry weight of seedlings, and on mycelial growth, spore germination and number of germtubes per spore. The highest inhibition of bean germination was observed in aqueous and ethanol lablab extracts (60%) compared to the control with increased mean germination time (7 days) and corresponding decrease in germination index (2) and final germination percentage. Aqueous extract of lablab resulted in significantly high spore germination percentage (84%) with pronounced effect on germtube length (8%) and number of germtubes by 13% more than the control. Aqueous lablab extracts inhibit germination and stimulates germination of Fusarium spores that may be responsible for reduced germination and establishment of beans.