A regression approach for comparing field resistance of peanut cultivars to tomato spotted wilt tospovirus

Relationships between one TSWV susceptible peanut cultivar (Georgia Runner), one moderately resistant peanut cultivar (C-99R), and the current standard cultivar (Georgia Green) in the southeastern United States were examined. Both moderately resistant cultivars had greater field resistance and higher yields than the susceptible cultivar, Georgia Runner, regardless of the level of disease pressure. Linear regression revealed that under heavy disease pressure, C-99R appears to exhibit greater disease resistance than has been previously reported for Georgia Green and other currently available cultivars. Only 13% and 33% of the variation in yield difference between cultivars could be explained by differences in TSWV incidence for C-99R and Georgia Runner, respectively, when compared by linear regression with Georgia Green. Although the correlations were weak for these relationships, the relationships were still significant (P < 0.05). Linear regression equations allow us to designate TSWV risk assesment index scores for cultivars relative to scores for the standard Georgia Green. Such a comparison allows for an examination of the relative levels of resistance observed among cultivars under varying levels of disease pressure. This type of analysis would be most useful under heavy disease pressure situations, when the predictive power of this analysis is greater and differences in field resistance between cultivars would be most significant. (C) 2002 Elsevier Science Ltd. All rights reserved.