Abstract
Significant increases in pre-emergence seedpiece decay and preemergence shoot infection were observed asErwinia carotovora var.atroseptica inoculum density increased. As inoculum density increased, a point was reached where virtually 100 per cent of the disease was expressed as preemergence decay and no typical postemergence blackleg occurred.
Soil temperature and soil moisture markedly affected blackleg incidence, especially at low inoculum densities. Increasing soil temperature (from O°C to 30°C) and soil moisture (from 65 to 100% of field capacity) usually resulted in an increased total blackleg incidence. The effect of soil temperature and soil moisture appeared to be masked at high inoculum densities. Conditions such as low inoculum density and/or cool soil temperatures and low soil moistures which apparently slowed the rate of seedpiece decay usually increased the amount of postemergence blackleg, but also reduced the total amount of disease which occurred.
It is suggested that conditions which are not optimal for the pathogen result in increased amounts of typical easily diagnosed postemergence blackleg expression, whereas conditions which favor the pathogen may reduce this phase of the disease but actually increase the total loss by increasing the amount of seedpiece decay and preemergence death of potato shoots.
Resumen
Incrementos significativos en pudrición de semilla antes de la emergencia y en infección del brote antes de su emergencia fueron observados cuando se aumentó la concentración de inóculo deErwinia carotovora var.atroseptica. A medida que la concentración de inóculo fue en aumento se llegó a un punto donde virtualmente 100% de la enfermedad fue expresada como pudrición de preemergencia y no ocurrió tipico piema negra. La temperatura y humedad del suelo afectaron marcadamente la incidencia de pierna negra, especialmente a bajas concentraciones de inóculo. Aumentos de la temperatura del suelo (desde 0°C a 30°C) y de la humedad del suelo (desde 65 a 100% de capacidad de campo) resultaron generalmente en un incremento de la incidencia total de pierna negra. Los efectos de temperatura y humedad del suelo parecen ser enmascarados a densidades altas de inóculo. Condiciones tales como baja densidad de inoculo y/ó bajas temperaturas del suelo, y baja humedad del suelo, factores que generalmente decrecieron la cantidad de pudrición de semilla, aumentaron generalmente la cantidad de pierna negra después de la emergencia, pero redujeron la cantidad total de enferme dad que ocurrió.
Se sugiere que condiciones que no son optimas para el patógeno resultan en aumento de incidencia de pierna negra post-emergente de fácil diagnóstico, mientras que cuando las condiciones favorencen al patógeno se puede reducir ésta fase de la enfermedad, pero incrementa el total de pérdidas por incremento de la cantidad de pudrición de semilla y muerte de brotes antes de la emergencia.
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Formerly Graduate Research Assistant.
This work was supported by the Colorado State University Experiment Station. Published as Scientific Series Paper No. 2263.
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Aleck, J.R., Harrison, M.D. The influence of inoculum density and environment on the development of potato blackleg. American Potato Journal 55, 479–494 (1978). https://doi.org/10.1007/BF02852154
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DOI: https://doi.org/10.1007/BF02852154