Synchytrium solstitiale: reclassification based on the function and role of resting spores

Area of Science:

• * Mycology
• * Plant Pathology
• * Biological Control

Background:

• * Synchytrium solstitiale causes false rust disease in yellow starthistle (YST).
• * Understanding its life cycle is crucial for developing biological control strategies.
• * The role and germination of resting spores were previously unclear.

Purpose of the Study:

• * To develop a protocol for Synchytrium solstitiale resting spore germination.
• * To investigate the long-term survival and viability of these resting spores.
• * To clarify the life cycle and taxonomic placement of S. solstitiale.

Main Methods:

• * Incubation of dried leaves containing resting spores on water agar at 10-15°C.
• * Storage of air-dried leaves at room temperature for viability assessment.
• * Inoculation of YST with germinated resting spores and observation of disease development.
• * Morphological and biological comparison of resting and sporangial galls.

Main Results:

• * Resting spores germinated after 7 days of incubation, releasing zoospores.
• * Spores remained viable after over 2 years of storage in dried leaves.
• * Germinated resting spores successfully infected YST, causing typical false rust symptoms.
• * Distinct morphological and biological differences were observed between resting and sporangial galls.

Conclusions:

• * Resting spores are critical for the long-term survival and off-season persistence of S. solstitiale.
• * The completion of the S. solstitiale life cycle under controlled conditions was confirmed.
• * Based on spore morphology and function, S. solstitiale should be reclassified as diheterogallic and placed in the subgenus Exosynchytrium.