THE PROBABILITY OF DETECTING CLAVIBACTER-MICHIGANESIS SUBSP SEPEDONICUS BY INDEXING SEED POTATO LOTS WITH SEROLOGICAL TESTS

Detection of the bacterial ring pot pathogen (Clavibacter michiganensi s subsp. sepedonicus) in seed potato lots by laboratory indexing compl ements visual inspection. The probability of detecting symptomless inf ections is a function of sample size and incidence of infection. We de termined the incidence of asymptomatic stem and tuber infections in fo ur potato cultivars at three levels of inoculum. At the high inoculum level, 51-93% of stems were infected at 80 days after planting, and 10 -59% of the tubers were infected at harvest. The effect of the differe nt percentages of infected stems and tubers on the probability of dete ction for simple random sampling was calculated for a constant sample size. The actual detection levels for two cultivars planted in field p lots with predetermined incidence levels of ring rot infected plants w ere reasonably close to predicted probabilities.