Biotic controls, defined

Since the symbiotic interactions of grasses are highly variable for each specific defensive toxin, it is up to the researcher to find that important combination that can be exploited for the desired control. The approach used to define nematode resistance and control should involve extensive surveys of clonal types conducted under field conditions where the desired nematode species exist. Thus, nematode resistance to specific species should be conducted in symbiotic grass fields in soils that have been shown to have that nematode. A clonal line within this location must be checked for its endophyte status, since other factors, biotic and abiotic, might also account for apparent nematode resistance, as demonstrated by the results of Bernard et al. (1998) and reflected in the report of Cook et al. (1999), which identified several ryegrass clones that were resistant to M. naasi, although the final analysis showed that all were endophyte-free. 

---