The Use of Disease Severity Variables in Predicting the Efficacy of FOV4 Resistance Selection

In 2015, several hundred cultivars and germplasm lines of upland (Gossypium hirsutum) and pima (G. barbadense) cotton were evaluated for disease performance under pressure of Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) in replicated trials between two field sites located in the central and southern areas of California’s San Joaquin Valley. Disease severity was measured by foliar symptoms, vascular root staining, and plant survival. We analyzed their correlative relationships to one another to evaluate the predictability of one variable response from the other variable-observation. Analyses were performed as a way of testing the efficacy and biological importance of each variable with respect to its ability to aid the selection of FOV4 resistant lines. Results from this research demonstrated that FOV4 foliar symptom was a reliable predictor of vascular root staining symptoms. In addition, analyses showed a statistically significant tendency toward increased variability with decreased symptom severity. In other words, the worst observed symptoms were proven to be most reliable for ejecting poor performing lines, providing a better resistance selection efficacy.