Pseudomonas tolaasiiin cultivated mushroom (Agaricus bisporus) crops: numbers of the bacterium and symptom development on mushrooms grown in various environments after artificial inoculation

摘要

The recovery ofPseudomonas tolaasiiapplied to peat, limestone and mushroom caps, is very difficult, recovery rates being 0.2–16.0. WithoutAgaricus bisporusmycelium, inoculatedPs.tolaasiidisappears in the casing layer. As mushroom primordia grew in size on inoculated mushroom beds, the number of detectable cells of the pathogen increased. Symptoms of blotch disease became visible when 5.4 times 106cfu were detectable, when the mushroom primordia were 6 mm in diameter; 60 of mushrooms showed symptoms before they were 15 mm in diameter. Application ofPs.tolaasiicells as low as 20 cfu/cm2of bed gave epidemics of this severity. Neither size nor age of mushrooms affects their susceptibility. WhenPs.tolaasiiwas placed directly onto caps, 6 times 107cfu were necessary to produce a blotch lesion (though only 3.5 times 106cfu could be recovered). Changes in r.h. and temperature did not affect the numbers of cells ofPs.tolaasiion inoculated caps; very frequent watering did so. Increased severity of the disease was seen only on over‐watered mushrooms; this occurred by increase in the size of lesions seen at the primordium stage. The number of cells ofPs.tolaasiipresent on the early primordial stages of mushroom growth controls the extent of blotch disease seen at harvesting, whereas variations in r.h. or temperature during growing do not do so. An illustrated disease symptom measurement key (of general application for assessing severity of blotch disease) is included in the t