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Title: COMPARISON OF LEAF AREA INDEX WITH ROOT WEIGHT FOR ASSESSING PLANT DAMAGE BY SOILBORNE PATHOGENS

Author
item BIERNACKI, MACIEJ - OKLAHOMA STATE UNIV.
item Bruton, Benny

Submitted to: Cucurbitacea
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Vine decline is a broad term used to describe a disease syndrome in cucurbits in which the vines begin to collapse and die as the fruit approach maturity. Numerous fungi have been associated with vine declines in melons. Many of the associated fungi have been inoculated to melons to verify pathogenicity. Historically, root weight in conjunction with root disease ratings have been used to evaluate pathogenicity and level of fungal virulence. Because of the great variability in root weights of inoculated vs. non-inoculated plants, scanner-based image analysis was used to determine the plant characteristics most responsive to inoculation with root rot pathogens. Cumulative surface area of the first three true leaves was 3.5 times more precise in detecting plant damage as compared to root weight. Standardized to common scale, quantitative assessment of plant damage, using leaf area index, has great potential as a tool for precise and accurate determination of plant resistance and/or virulence of root ro pathogens in cucurbits.

Technical Abstract: Melon (Cucumis Melo) cvs. 'Hymark' or 'Mission' were grown in growth chambers over 4 weeks in sand inoculated with soilborne pathogens Monosporascus cannonballus, Acremonium cucurbitacearum, or Rhizopycnis vagum. Quantitative information on plant characteristics and biomass was collected from destructively sampled plants. Leaf surface area and root mass decreased in plants proportionally to disease severity. Both, the leaf area index or root mass were significantly correlated with disease severity index. However, leaf area index was 3.5 times more precise and more likely to reflect damage to plant roots than shift in root mass. Leaf area index was capable to detect significant difference in root damage even in cases where root mass measures would fail to do so. The leaf area index is particularly suitable for nondestructive continuous evaluation of plant impairment. Standardized to common scale, quantitative assessment of plant timpairment using leaf area index has great potential as a tool for precise and accurate assessment of plant resistance and/or pathogen virulence. The index may facilitate spatial and temporal comparisons and meta-analyses of data for cucurbits.