Rhizobium strain requirements for improved nodulation of Lotus corniculatus

Farmers in New Zealand have reported seedling establishment problems with Lotus corniculatus. Field trials have indicated that partial or complete nodulation failures can occur due to the rapid death of rhizobia on the seed. Fifteen strains of Rhizobium loti, prepared as peat inoculant, were evaluated for survival on inoculated seed of L. corniculatus, and for ability to nodulate such seed when oversown into native grassland. Survival of rhizobia after 24 h varied from 1 to 89%. There were significant differences between strains in the percentage of seedlings nodulated. The currently recommended New Zealand strain (ICMP 9005) performed poorly, with only 1% of rhizobia surviving on the seed and 7% of plants nodulated. The results indicate that nodulation problems with L. corniculatus in New Zealand can be overcome by selecting strains with better survival and nodulation characteristics. Determination of survival rates on the seed offers a rapid laboratory screening method for initial evaluation of rhizobia for inoculant use.