This is a separate characteristic from resistance to infection. The type of resistance available depends on the specific disease. Most hybrids and varieties have some level of polygenic resistance to common diseases. This resistance is usually adequate, although a small amount of yield loss may occur. When disease pressure is very high, more resistance may be needed.
Plant breeders breed for high levels of specific resistance to certain diseases.
Check with your seed company representative for information on the best seed for your situation. A summary of the types of resistance you can expect to find in common hybrids and varieties follows. Most hybrids grown in Iowa have some polygenic resistance to common foliar diseases including rust, northern leaf blight, anthracnose, gray leaf spot, and northern leaf spot. Some hybrids are more resistant than others. Stay-green is related to this characteristic.