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The reduction in seed quality (Q) could be a measure of field emergence, or a combination of germination before and after accelerated aging, field emergence, and electrolyte conductivity. For these purposes, the specific measure of seed quality is unimportant. The squared mean plant quality rating (S) divided by the maximum quality rating squared would likely yield a more representative curve than a cubic equation for seed quality. Any infection, evidenced by symptoms and signs of pathogens on the stems and pods, could lead to seed infection and reduced seed quality. However, the higher the disease severity, the better the chance that the infection has reached the seed, hence the squared term to describe this type of relationship. The maximum
quality reduction (P) would have to be determined experimentally. By whatever means used to measure Q1, be it on a scale of 0 to 25 or in percent, M would also have to appear in the same form. An appropriate value for (P) could be 100% of the scale used, with a much delayed harvest. Under normal conditions, 20% of the range of the {S scale would be a reasonable value. The seed quality reduction from infection by pathogens would be difficult to separate from physiological decline, and both may have to be included in equation 3. A factor multiple by the number of days after the