| Popis: |
The effects of inoculum dose, inoculation method, temperature and soil water potential on transmission of bacterial blight (Pseudomonas syringae pv. pisi) from seed to seedling of pea (Pisum sativum) were examined in two separate experiments. Pea seed (cv. Solara), artificially inoculated with different concentrations of bacteria by dipping or vacuum infiltration, or naturally infected, was sown in pots which were maintained at different soil water potentials and temperatures. Dose received (mean number of bacteria per seed) and soil water potential had the greatest effects, with the proportion of plants infected and the mean number of lesions increasing with dose received and soil moisture. Inoculation method had little direct effect on transmission but greatly influenced the dose received. Temperature, in the range 5 to 18°C, had no effect on the number of lesions and little effect on the proportion of plants infected. Generalized linear models were derived relating the proportion of plants infected, p, and the mean number of lesions, m, to the dose received, d, and the soil water potential, ψ. The equations were : p = 1 -exp [-0.064d 0.24 exp (58.5ψ)] and m = 0.24d 0.25 exp (93.3ψ). The exponents for dose in these equations were considerably less than the theoretical value of one implied by a one-hit model and suggested considerable heterogeneity in the one-hit probability. Some possible explanations for this are considered. |
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