Untersuchungen zur bakteriellen Erkrankung Acidovorax ...

SUMMARY
6 SUMMARY
The aim of this study was to contribute to clarifying the epidemiology of the
phytopathogenic bacterium Acidovorax valerianellae on corn salad [Valerianella
locusta (L.)]. To this end, research was conducted on infection conditions, cultivar
sensitivities, transmission paths and seeds. Based on these results, control strategies
shall be demonstrated.
The tests performed under infectious conditions revealed that the infection of
A. valerianellae is dependent on temperature, leaf age, inoculum concentration and
leaf moisture, as well as the relative humidity. Inoculation was possible at
temperatures between 10 °C and 30 °C. It was possible for leaves of any age to be
infected. Moreover, infection was independent of the inoculum concentration, and
occurred between 10 2 and 10 7 cfu/ml. The speed of infection and the characteristics
of the symptoms increased with increasing temperature, leaf age and inoculum
concentration. Both the duration of leaf moisture and the relative humidity played a
crucial role in the infection process. Under dry conditions, inoculated corn salad
plants developed no symptoms. However, infestation increased significantly under
humid conditions or during humid periods. Five hours of leaf moisture sufficed for
an infection to occur.
It was demonstrated that targeted dry growth conditions with short leaf moisture
periods constitute an option for controlling A. valerianellae.
All 13 tested commercial corn salad cultivars were prone to A. valerianellae.
However, the resistance of the wild type V. rimosa was confirmed.
For this reason, it seems advisable to cross the wild type with commercial cultivars.
A. valerianellae endured for up to eleven months in the soil. Some of the corn salad
cultivars cultivated immediately (and one up to eleven months, respectively) after
infected plants were severely infected. The number of infected plants decreased in
line with increased rotting of infected old plant material.
A cultivation break of at least twelve months and the rotation of crops therefore
appear to be appropriate ways to eliminate A. valerianellae from the soil.
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