VIEW ARTICLE

Resistance

Apparent Sap Flow Velocity in Peanut Genotypes Susceptible and Resistant to Verticillium dahliae. P. I. Erickson, Research associate, Department of Agronomy, Oklahoma State University; H. A. Melouk(2), and D. L. Ketring(3). (2)(3)Research plant pathologist and plant physiologist, U.S. Department of Agriculture, Agricultural Research Service, P.O. Box 1029, Stillwater, OK 74076. Phytopathology 76:500-502. Accepted for publication 21 November 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1986. DOI: 10.1094/Phyto-76-500.

The thermoelectric (heat pulse) method, which is used for measuring apparent sap flow velocities (AS_v) in living plants, was studied to determine whether it could be used to detect sap flow differences between peanut (Arachis hypogaea) genotypes susceptible and resistant to Verticillium dahliae. Two peanut genotypes differing in disease sensitivity (susceptible cultivar Tamnut 74 and resistant cultivar PI 295233) were evaluated in two greenhouse experiments by inoculating plants with 0.5 ml of conidial suspension (5 x 10⁵ conidia per milliliter) of V. dahliae 44 days after planting. Both genotypes grown with and without V. dahliae were compared for differences in AS_v at 43, 47, 50, 57, 64, 71, 78, 84, 91, and 98 days after planting. Plant water loss was monitored periodically throughout the study. At harvest (105 days after planting), disease index and biomass (vegetative and reproductive) production were also determined. Significant differences in genotype AS_v response to infection by V. dahliae were found in both experiments, with significant temporal differences for each genotype. Significant reduction in AS_v occurred in inoculated PI 295233 (47-50 days after planting), but were less than 10% at 71 days after planting. Tamnut 74 showed consistent AS_v reductions 57-98 days after planting, but not earlier. Differential genotype response to V. dahliae were also reflected in the plant water loss, biomass production, and disease index data. The thermoelectric method effectively detected the difference between peanut genotypes susceptible and resistant to V. dahliae: significant differences in AS_v were found among treatments in both experiments, and coefficients of variation were low.