SEED EXTRACT PCR. In this method, bacterial extract from seeds is tested by PCR. The success of this test depends upon the extraction of pathogens from the seeds into the liquid, lack of chemical or biological inhibitors, and the specificity of the primers. Although, we have been using the method successfully, there is a potential possibility of obtaining false negatives (due to inefficient extraction of bacteria from certain internally-infected seed lots, chemical or biological inhibition due to seed treatments, and failure of primers to react with certain strains of the pathogen) and false positives (due to cross reaction of primers with certain strains of the non-pathogens).
BIO-PCR. In this method, bacterial extract from seeds is plated onto selective media and the bacterial harvest from plates is tested by PCR. The success of this test depends upon the extraction of pathogens from the seeds into the liquid, ability of the pathogen to grow on selective media, and the specificity of the primers. Although, we have been using the method successfully, there is a potential possibility of obtaining false negatives (due to inefficient extraction of bacteria from certain internally-infected seed lots, inability of certain strains to grow on selective media, and failure of primers to react with certain strains of the pathogen) and false positives (due to cross reaction of primers with certain strains of the non-pathogens).
SEEDLING PCR. In this method, seedlings are grown under controlled conditions and bacterial extract from seedlings is tested by PCR. The success of this test depends upon successful transmission of bacteria from seeds to seedlings and the specificity of the primers. Although, we have been using the method successfully, there is a potential possibility of obtaining false negatives (due to inefficient transmission of pathogen from seeds to seedlings from certain seed lots, and the failure of primers to react with certain strains of the pathogen) and false positives (due to cross reaction of primers with certain strains of the non-pathogens).
LIQUID PLATING. In this method, bacterial extract from seeds is dilution plated onto selective media and suspect colonies are tested to identify the pathogen. The success of this test depends upon successful extraction of the pathogen into liquid and the selectivity of the media. Although, we have been using this method successfully, there is a potential possibility of obtaining false negatives (due to inefficient extraction of bacteria from certain internally-infected seed lots, inability of certain strains to grow on selective media, and interference in plate reading by other bacteria) and false positives by ability of other bacteria to cause borderline symptoms in the pathogenicity tests.