Relationships among symptoms of spotted wilt disease of peanut and their potential impact on crop productivity and resistance breeding
Symptoms of spotted wilt of peanut were evaluated in a field experiment over three years (2010–2012) near Marianna, Florida. Assessment included three visual measures of disease and ImmunoStrip (a form of ELISA) testing of root crowns for the presence of Tomato spotted wilt virus (TSWV), the causal agent of spotted wilt in peanut. Foliar symptoms of spotted wilt on a 1 to 10 scale and on a disease incidence rating (DIR) were highly correlated (r = 0.88; p < 0.001). Foliar symptoms were moderately correlated (0.45 < r < 0.54; p < 0.001) with TSWV infection. However, symptoms on the testa were highly correlated with TSWV infection (r = 0.78; p < 0.001). These results indicate that foliar symptomology is less reliable in assessing TSWV infection than testa symptomology. Regression analysis showed that foliar symptoms underestimated the proportion of plants infected by TSWV. Seed inspection may be a good predictor of plant infection and therefore useful in breeding programmes because it is much less expensive than ELISA. Resistance to TSWV infection is characteristic of some resistant peanut genotypes and a lack of testa symptomology could help to identify those genotypes.