Plant Cell Rep (2004) 22:608–614 DOI 10.1007/s00299-003-0733-3 PHYSIOLOGY AND BIOCHEMISTRY E. Ait Barka · P. Eullaffroy · C. ClØment · G. Vernet Chitosan improves development, and protects Vitis vinifera L. against Botrytis cinerea Received: 15 April 2003 / Revised: 25 September 2003 / Accepted: 25 September 2003 / Published online: 1 November 2003  Springer-Verlag 2003 Abstract We evaluated the potential of chitosan both to stimulate plant development and to induce protection from Botrytis cinerea in Vitis vinifera L. plantlets. The presence of 1.75% (v/v) chitogel in the culture medium was the optimal concentration for in vitro grapevine plantlet growth, as determined by measurements on enhancement of root and shoot biomass. Photosynthesis and related parameters were also stimulated in chitogel- treated plantlets. Chitogel reduced the development of Botrytis cinerea and induced cytological alterations to the pathogen. When challenged with the fungus, a significant decrease in disease incidence was observed in plants growing on medium supplemented with chitogel. Fur- thermore, exogenous foliar applications of chitogel to plantlets growing on chitogel-free medium sensitized them so as to be protected against Botrytis cinerea attack. Our results indicate that chitogel can be used in the vineyard as a means to attain protection against Botrytis cinerea and that its application may counteract the wide use of chemical pesticides. Keywords Botrytis cinerea · Chitogel · Bioorganic substance · Vitis vinifera L. Introduction Plant disease resistance can be defined as the ability of plants to prevent or restrict pathogen growth and multi- plication. Gray-mould diseases caused by Botrytis cinerea are probably one of the most common and widely distributed diseases of vegetables, fruits, and even field crops throughout the world. This fungus causes one of the most economically important diseases of grape, resulting in heavy losses of yield in table and wine grapes in many locations world wide (Elad 1994). Fungicides are effective in reducing the damage to plants caused by fungal pathogens, but repeated fungicide applications are harmful to the environment (Siedlecka and Krupa 1996). Furthermore, chemical control of B. cinerea has only been partially successful due to the continual appearance and establishment of resistant Botrytis spp. strains to these chemicals. The development of pesticide-resistant strains, which would eliminate the use of pesticides, is a goal of considerable interest within the framework of a sustainable, economically profitable agriculture. Consequently, the possibility of stimulating internal plant defenses has become an interesting option for enhancing natural disease resistance. Among the elicitors known to date, chitosan, a polycationic b-1,4-linked-d-glucosamine polymer, has the best prospects as a biocontrol agent (El Ghaouth et al. 1994). Chitosan and its derivatives, such as glycol- chitosan and carboxymethylchitosan, are known to form a semi-permeable film around plant tissues, they are inhibitory to a number of pathogenic fungi, and they also induce host-defense responses (El Ghaouth et al. 1994). The application of a chitosan solution may sensitize the plants to respond more rapidly to pathogen attack by stimulating chitinase and glucanase production (Ben- hamou 1996). Thus, there is a growing interest in the use of chitosan as a means to providing more protection against plant pathogens since it has been shown to have a wide range of anti-fungal activity (El Ghaouth et al. 1992a, 1992b, 1994). Several investigators have reported that dipping strawberry fruit in a chitosan solution Communicated by S. Gleddie E. Ait Barka ( ) ) · C. ClØment UFR Sciences, URVVC, UPRES EA 2069, Laboratoire de Biologie et Physiologie VØgØtales, UniversitØ de Reims Champagne-Ardenne, B.P. 1039, 51687 Reims Cedex 2, France e-mail: ea.barka@univ-reims.fr Tel.: +33-3-26913441 Fax: +33-3-26913427 P. Eullaffroy · G. Vernet UFR Sciences, URVVC, UPRES EA 2069, Laboratoire d’ Eco-Toxicologie, UniversitØ de Reims Champagne-Ardenne, B.P. 1039, 51687 Reims Cedex 2, France