Allelopathic interference of annual ryegrass (Lolium rigidum) onlucerne nodulation

摘要

Laboratory and glasshouse experiments were undertaken to evaluate the allelopathic effects of annual ryegrass (Lolium rigidum Gaudin, ARG) root exudates against growth and nodulation of lucerne genotypes. This paper reports the outcomes of the nodulation investigation. The impact of ARG on lucerne nodulation was evaluated using SARDI Five and Titan 9 lucerne cultivars (in both laboratory and glasshouse) at 6 rhizobium (Sinorhizobium spp.) concentrations (0, 0.6, 1.5 * 10, 1.5 * 102, 1.5 x 10 1.5 x 104 colony forming units mL~'). At the highest rhizobium concentration, a fivefold reduction in nodule number was observed in the laboratory when lucerne genotypes were grown with ARG. Increasing annual ryegrass density also reduced nodulation under glasshouse conditions. The variability identified within and between lucerne populations suggests that there is scope to reduce allelopathic interference of ARG on seedling lucerne growth and improve the compatibility of these species in pasture mixtures at establishment.