Comparing predictions from mixed model equations with host range determinations from historical disease evaluation data of two previously released weed biological control pathogens

Abstract

Host range determination is essential to risk assessments of classical biological weed control agents and needed for petitions to release of agents into non-native areas. Recently Henderson’s mixed model equations (MME) were adapted to evaluating host ranges of two biological control pathogens. This was accomplished by incorporating genetic relatedness, in the form of DNA sequences, with disease evaluation data among target and non-target plants to generate best linear unbiased predictors (BLUPs) of disease reaction among these plant species. Although qualities of MME analysis provide inherent validation of the approach, it has been difficult to validate by comparison with historical host range determination or field data. These types of data are virtually non-existent, because original, raw host range data from replicated tests have, for the most part, been lost, and host-range data from tests or monitoring of multiple plant species in the field are extremely limited. In this study, the host-ranges of two biological weed control pathogens previously released in the USA were re-evaluated with the MME and historical host-range data. Results showed that: BLUPs confirmed the narrow host range of the two pathogens; BLUPs supported and substantiated currently available information on host range; BLUPs were accurate predictors of host range, particularly concerning susceptibility of any non-target species in the field; and no new, unforeseen non-target effects could be expected in nature on the basis of BLUPs. Thus, validation was made for MME analysis in predicting known field host-range from greenhouse data.