White rust, caused by the oomycete, Albugo occidentalis, is a major foliar disease of spinach grown in the eastern production areas of the United States.
White rust, caused by the oomycete, Albugo occidentalis, is a major foliar disease of spinach grown in the eastern production areas of the United States. White rust reduces spinach quality, which causes a greater economic loss than the effect of white rust on yield. Spinach, for both fresh market and processing, is graded on the basis of the amount of leaf area with white rust lesions. The grade of the raw product, for processing, is determined by the percentage of spinach leaves with lesions of a certain size.
Albugo occidentalis is an obligate parasite, which attacks spinach as well as the weed strawberry blite (Chenopodium capitatum, on which it was first reported in 1903 in Colorado. Its host range is confined to Spinaciaand several species of Chenopodium. Formerly a member of the kingdom Fungi, A. occidentalis is now considered a member of the kingdom Stramenopila or Chromista.
Initial symptoms of white rust appear as small chlorotic areas on the upper leaf surface. As the disease progresses, small white and shiny blister-like pustules called sori are produced on the underside of the leaf and occasionally on the upper leaf surface. The pustules are also occasionally produced on petioles, branches, and fruit coats. Pustules may be oval, irregularly oval, or elongated and their size can vary from 0.5 to 2 mm in diameter to 3 to 4 mm in length.
This “white rust,” or Albugo occidentalis, has no central nervous system, but it is able to respond to stimuli through tropisms–directional movement responses that occur in response to a directional stimulus. These tropisms spark the zyphae or zoospore to approach or diverge from the source of the physical stimulus. Among the stimulus perceived by fungi are contact, chemicals, electrical potentials, air currents, gravity, and centrifugal forces. These sensory mechanisms require: a sensory mechanism to detect the stimulus, a reaction mechanism to respond to signals from the sensory mechanism, and a transduction mechanism to transmit signals from the sensory mechanism to the reaction mechanism.
White rust, caused by the oomycete, Albugo occidentalis, is a major foliar disease of spinach grown in the eastern production areas of the United States. White rust reduces spinach quality, which causes a greater economic loss than the effect of white rust on yield. Spinach, for both fresh market and processing, is graded on the basis of the amount of leaf area with white rust lesions. The grade of the raw product, for processing, is determined by the percentage of spinach leaves with lesions of a certain size.
Albugo occidentalis is an obligate parasite, which attacks spinach as well as the weed strawberry blite (Chenopodium capitatum, on which it was first reported in 1903 in Colorado. Its host range is confined to Spinaciaand several species of Chenopodium. Formerly a member of the kingdom Fungi, A. occidentalis is now considered a member of the kingdom Stramenopila or Chromista.
Initial symptoms of white rust appear as small chlorotic areas on the upper leaf surface. As the disease progresses, small white and shiny blister-like pustules called sori are produced on the underside of the leaf and occasionally on the upper leaf surface. The pustules are also occasionally produced on petioles, branches, and fruit coats. Pustules may be oval, irregularly oval, or elongated and their size can vary from 0.5 to 2 mm in diameter to 3 to 4 mm in length.
This “white rust,” or Albugo occidentalis, has no central nervous system, but it is able to respond to stimuli through tropisms–directional movement responses that occur in response to a directional stimulus. These tropisms spark the zyphae or zoospore to approach or diverge from the source of the physical stimulus. Among the stimulus perceived by fungi are contact, chemicals, electrical potentials, air currents, gravity, and centrifugal forces. These sensory mechanisms require: a sensory mechanism to detect the stimulus, a reaction mechanism to respond to signals from the sensory mechanism, and a transduction mechanism to transmit signals from the sensory mechanism to the reaction mechanism.