THE INCIDENCE OF RACES OF PSEUDOMONAS-SYRINGAE PATHOVAR PISI IN UK PEA (PISUM-SATIVUM) SEED STOCKS, 1987-1994

The incidence of pea bacterial blight infection in UK pea seed stocks between 1987 and 1994 is reported, The race structure of Pseudomonas s yringae pv. pisi isolates from the infected seed samples was investiga ted. The data suggested that the incidence of infection, across all ca tegories of seed tested has increased steadily over the last eight yea rs from 8.2% infected in 1987 to 36.5% in 1994. The most significant i ncrease followed removal of statutory certification controls in 1993. Race 2 of the pathogen was most frequently isolated from infected seed samples (65% to 92%) in all years. The frequency of infection by race 6 appears to have increased between 1987 and 1994, from 7% to 26% of the infected seed samples. In each year of the study between one and s even seed stocks were infected with more than one race of the pathogen , in particular races 2 and 6 were most frequently detected together. The implications of these findings are discussed in the context of pea production in the UK.