INGRESS OF THE WATERMELON FRUIT BLOTCH BACTERIUM INTO FRUIT

Bacteria were observed with the scanning electron microscope to be loc ated randomly on watermelon (Citrullus lanatus) fruit surfaces 2 hr af ter inoculation with drops of suspensions of the fruit blotch bacteriu m. For the next 4 days, bacteria were observed around and in stomata. Nine days after inoculation, masses of rod-shaped bacteria were observ ed in stomatal chambers. The incidence of disease decreased with age o f the fruit at the time of inoculation. The incidence of plugging, or covering, of stomata in the fruit with wax progressively increased wit h fruit age and appeared to provide a morphological barrier to bacteri al ingress. The observations were consistent with the concept that the pathogen enters the fruit through stomata and that immature fruit are the most likely to be infected.