STUDIES IN THE RELATIONSHIP OF EELWORMS AND BACTERIA TO CERTAIN PLANT DISEASES

Abstract

Two types of organism are known to be present in strawberry plants suffering from cauliflower disease, namely, eelworms, Aphelenchoides ritzema‐bosi and/or Aphelenchoides fragariae, and a bacterium, Corynebacterium fascians. Neither type, inoculated separately, has consistently reproduced the disease.An experimental investigation of a possible obligate etiological relationship between the eelworm and the bacterium is described, in which Aphelenchoides ritzema‐bosi and several strains of Corynebacterium fascians were inoculated together and separately.No abnormalities appeared in the absence of the eelworm. Typical cauliflower symptoms were reproduced only by a combination of the eelworm and strains of C. fascians originally isolated from cauliflower strawberries. Small alaminate leaves and enations appeared in all treatments where the eelworm was introduced, including those where no bacteria were co‐inoculated. Subsequent isolations, however, demonstrated the presence of contaminant strains of C. fascians in the latter plants. The severity of the enation symptom was related to the presence of a particular strain of C. fascians, but the alaminate leaves showed no such correlation. Evidence on the source of the contaminant strains found in the experimental plants is discussed.In parallel field investigations it was established that eelworm‐infested strawberries showing no cauliflower symptom frequently bore alaminate leaves, with which C. fascians was consistently associated. It is suggested therefore that cauliflower is simply the least frequent of a range of symptoms of a bacterial disease endemic in strawberry plants infested with Aphelenchoides spp.