Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2000
Publication Date: N/A
Interpretive Summary: Roots are not amenable to study due to their growth in non-transparent growing media and spatial properties like numerous modular roots, hierarchical branching, small diameters, and root tapping. Consequently, the study of roots in response to root rot pathogens is difficult. The use of digital scanner to capture plant images circumvented the need for adjustments to focus and/or lighting that would be required with a camera based imaging system. Scanner based measurements are more objective compared to manual measurements that may be strongly affected by experience and visual illusions of a scorer. Application of digital imaging technology in association with multi-variate statistics allowed for time and cost effective data collection and analysis, and provided a reliable tool for studying plant response to selected soilborne pathogens. Sensitivity of the scanner based technology demonstrated that differences in level of virulence between isolates of the same fungal pathogen were possible. The system provides an accurate and sensitive method to study virulence within the pathogen population as well as identify resistant plant genotypes.
Technical Abstract: The present study was designed to determine the effects of root rot pathogens on muskmelon. Plants were grown from seed in growth chambers for 28 day in sand inoculated with the soilborne pathogen Monosporascus cannonballus, Acremonium cucurbitacearum, or Rhizopycnis vagum. Images of plants were analyzed to quantify their performance. Muskmelon inoculated with pathogens had significantly increased mean root diameter (45%), decreased root length (26%), primarily in roots of < 0.5mm diameter, decreased number of root tips (27%), decreased rhizosphere volume (40%), and decreased cumulative and mean surface area of leaves (24%). Effects of M. cannonballus on muskmelon were significantly different from effects of other pathogens. Differences between effects of pathogen isolates on muskmelon were greater in magnitude than the differences at species level. Multi-variate analyses of plant performance were more powerful than uni- variate analyses to distinguish among effects of pathogen species and pathogen isolates. Discriminant analysis identified effects of each species of pathogen and their isolates on muskmelon and were useful to identify groups of plant traits modified by each fungal species or isolate, even at low disease levels. Digital image analyses proved to be a useful technique in quantitative assessment of plant damage caused by exposure to soilborne root rot pathogens.