Evaluation of host resistance and intercropping for management of the northern root-knot nematode in sainfoin, Onobrychis viciifolia

Sainfoin, Onobrychis viciifolia Scop., is an introduced forage legume grown on a limited basis in the Rocky Mountain region of the northern United States and southern Canada (Heath et al., 1973). The major attributes of sainfoin are its non-bloating characteristic as green forage and the high digestible nutrient content. It is drought tolerant, resistant to the alfalfa weevil, winter hardy, and produces good early spring growth tolerant to frost. If commercial Rhizobium inoculant is used, it requires no nitrogen fertilizer and has a low requirement for phosphorous. It has extremely good forage palatability. Therefore, it has the potential to provide a sustainable pasture system without required chemical inputs. The objective of our study was to determine if the combination of meadow bromegrass and our nematode-resistant sainfoin line would in crease the sustainability of sainfoin in the presence of the northern root-knot nematode (NRKN). Under environmentally controlled conditions, initial population density of five NRKN (Meloidogyne hapla Chitwood) eggs/cm³ soil resulted in 100% of sainfoin (Onobrychis viciifolia Scop.) roots with galls after70 days. One hundred percent of remaining sainfoin plants were galled in two other con trolled studies after 6 months, and 86% were galled in a field study after 2 years. Resistance to NRKN in an experimental sainfoin line was expressed in lower plant mortality, lower root galling, and lower egg production, compared to the susceptible cultivar Remont. The NRKN also appeared to be parasitic on roots of 'Regar' bromegrass (Bromus riparius Rehm.). Although root and shoot biomass were both reduced, there was no reproduction on roots and no bromegrass plants were killed. Under relatively high nematode soil populations, intercropping sainfoin with bromegrass provided no protection for sainfoin against the NRKN in either environmentally controlled or field plot studies. Our study further documents the extreme susceptibility [ABSTRACT FROM AUTHOR]