Journal of Chemical Ecology, Vol. 28, No. 8, August 2002 (  C 2002) Originally published online July 1, 2002, Rapid Communications, pp. RC7–RC14 (http://www.kluweronline.com/issn/0098-0331) EVIDENCE THAT RIBONUCLEASE ACTIVITY PRESENT IN BEETLE REGURGITANT IS FOUND TO STIMULATE VIRUS RESISTANCE IN PLANTS RICHARD O. MUSSER, 1,∗ SUE M. HUM-MUSSER, 2 SHANNON E. SLATEN-BICKFORD, 3 GARY W. FELTON, 4 and ROSE C. GERGERICH 3 1 Department of Entomology, University of Arkansas, Fayetteville, Arkansas, 72701 2 Department of Horticulture, University of Arkansas, Fayetteville, Arkansas, 72701 3 Department of Plant Pathology, University of Arkansas, Fayetteville, Arkansas, 72701 4 Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, 16802 (Received June 3, 2002; accepted June 25, 2002) Abstract—Phaseolus vulgaris L. cv. ‘Pinto’ bean is a local lesion host for the plant pathogen Southern bean mosaic virus (SBMV) and its vector is the Mexican bean beetle, Epilachna varivestis Mulsant. The objective of this study was to determine if prior feeding by the beetle would affect ‘Pinto’ bean’s resistance to SBMV and determine if ribonuclease (RNase), a major constituent of beetle regurgitant, mediated the plant’s response to the virus. ‘Pinto’ bean plants fed upon by beetles had increased resistance to plant viruses compared to non- wounded or mechanically wounded and buffer-treated plants. Plants that were mechanically wounded and treated with RNase had increased resistance to plant viruses that was equal to plants fed upon by adult beetles. The induction of plant pathogen defenses could be a good adaptation for the plant in the presence of a beetle and pathogen threat. This evidence suggests that RNase activity in the beetle regurgitant could function as an insect-derived elicitor of plant resistance to viruses. Key Words—Saliva, induced resistance, vector, virus, systemic acquired resistance, elicitor, ribonuclease, RNase, regurgitant. ∗ To whom correspondence should be addressed. E-mail: rmusser@ag.arizona.edu 1691 0098-0331/02/0800-1691/0 C  2002 Plenum Publishing Corporation