Relationship of age of sunflower seedlings to infection by Plasmopara halstedii

S. Sadaqat Mehdi and M. L. Carson

Abstract

The relationship of age of seedlings to infection by Plasmopara halstedii was studied by inoculating 3-day-old to 15-day--old sunflower seedlings. There appears to be a negative and significant correlation (r = -0.91**) between sunflower seedling age and percentage of seedling infection of downy mildew. Over 83% of the seedlings up to 8 days of age were susceptible to this pathogen. However, the l5-day-old plants showed some resistance. The percentage infection decreased with increase in age of plants.

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