|Oleson, Arland - NORTH DAKOTA STATE UNIV.|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1995
Publication Date: N/A
Technical Abstract: Clavibacter michiganense pv. insidiosum (Cmi), the causal agent of bacterial wilt in alfalfa, is spread primarily through infected plant material although seed transmission occurs at a low frequency. Phytosanitary laws in several countries require alfalfa seed to be certified free of Cmi. This study was initiated to determine the frequency of Cmi infestation in seed from infected plants, to develop seed lots with known levels of Cmi, and to develop rapid tests for detecting the bacterium. Interpollinations were made between highly infected plants of three varieties. Seeds were assayed in batches for Cmi by grinding and dilution plating the extract onto a semi-selective medium. Cmi was distinguished by colony morphology, KOH reaction, and a specific PCR-based assay. Cmi infected seed were produced by 7% of infected plants. Overall, infection occurred in 0.12-1.6% of seed. Seed collected from field-grown plants with severe bacterial wilt symptoms initially had mean Cmi levels o 300 million CFU/g, but populations decreased markedly when seed was stored at 24 degrees C.