Mapping the potato scab: spatial relationships, soil chemistry, leaf contents, and pathogenic dynamics

Abstract

Common scab caused by Streptomyces spp., causes considerable potato yield losses worldwide. Here, we aimed to study the correlation between common scab severity, and soil chemical characteristics and leaf nutrient contents. Data on potato yield, scab incidence, and soil characteristics obtained from 26 sampling points were subjected to multivariate analysis and then analyzed for spatial dependence. For most soil nutrients and pH, there was a inverse relationship with scab severity. Conversely, organic matter, S, Ca, and Mg contents positively correlated with scab damage. Leaf N, P, K, Ca, Mg, S, Cu, Mn, and Fe contents were inversely related severity, whereas B and Zn concentrations were closely associated with the disease. Differences in the relationship between foliar and soil nutrient contents greatly contribute to the complexity with which soil conditions affect the growth of Streptomyces spp. in the soil, and the plant chemical-physiological conditions. Our findings revealed that soil and foliar nutrient status affected the incidence of scab. Although most nutrients suppressed the disease, B and Zn showed a complex association with severity. These discrepancies likely arose from soil conditions, as pH and organic matter drive Streptomyces activity, while plant physiology modulates nutrient uptake and infection resistance.