ORIGINAL ARTICLE Crotalaria spectabilis and Raphanus sativus as Previous Crops Show Promise for the Control of Bacterial Wilt of Tomato Without Reducing Bacterial Populations Pe ´ ninna Deberdt 1 , Eric Goze ´ 2 , Re ´ gine Coranson-Beaudu 1 , Benjamin Perrin 1 , Paula Fernandes 1 , Philippe Lucas 3 and Alain Ratnadass 4 1 CIRAD, UPR HORTSYS, Campus Agro-environnemental Caraı¨be, Le Lamentin F-97285, Martinique 2 CIRAD, UPR AIDA, Montpellier TA B-115/02, F-34398, France 3 INRA, UMR IGEPP INRA/Agrocampus Ouest/Universit e de Rennes 2, Le Rheu BP 35327, F-35653, France 4 CIRAD, UPR HORTSYS, Montpellier TA B-103/PS4, F-34398, France Keywords bacterial wilt, biocontrol, Crotalaria spectabilis, previous crops, Ralstonia solanacearum, Raphanus sativus, tomato Correspondence P. Deberdt, CIRAD, Campus Agro-environnemental Cara € ıbe, Le Lamentin, Martinique. E-mail: peninna.deberdt@cirad.fr Received: April 24, 2014; accepted: Septem- ber 19, 2014. doi: 10.1111/jph.12333 Abstract Ralstonia solanacearum is responsible for bacterial wilt affecting many crops worldwide. The emergent population of R. solanacearum (phylotype IIB/ 4NPB) wilts previously resistant varieties and has rapidly spread through- out Martinique. No conventional method is known to control it. In this study, previous crops used as sanitizing crops were investigated as an environmentally safe alternative method of control. The ability of the emergent population of R. solanacearum to persist in planta and in the rhi- zosphere of Brassicaceae, Asteraceae and Fabaceae grown as previous crops was evaluated in controlled conditions, and the incidence of bacte- rial wilt was assessed in the following tomato crop. Results showed that all species carried R. solanacearum latently. Among Brassicaceae and Aster- aceae, the highest density of R. solanacearum was found in planta and in the rhizosphere of Tagetes erecta. The density of the R. solanacearum popu- lation in the rhizosphere of Raphanus sativus cv. Karacter was significantly higher than that in Raphanus sativus cv. Melody. In Fabaceae, the density of R. solanacearum population in planta was statistically similar in all spe- cies. The density of the R. solanacearum population in the rhizosphere of Crotalaria juncea was significantly higher than that in Crotalaria spectabilis. This study showed for the first time that Crotalaria spectabilis and Raphanus sativus cv. Melody grown as previous crops improve the performance of the following tomato with similar effects on R. solanacearum populations in the soil as bare soil. The incidence of the disease in tomato decreased by 86% and 60%, after R. sativus cv. Melody and C. spectabilis, respectively, and the proportion of infected plants also decreased. These results suggest that C. spectabilis and R. sativus cv. Melody can be used as previous crops to help bacterial wilt control in ecological management strategies without drastic suppression of R. solanacearum population in stem tissues and in the rhizosphere. Introduction Bacterial wilt caused by Ralstonia solanacearum is a major constraint for the production of many economi- cally important crops, including solanaceous plants (tomato, potato, tobacco and eggplant), banana and some ornamentals. This soil-borne vascular disease is widespread in tropical and subtropical regions of the world (Hayward 1991; Elphinstone 2005). In Marti- nique, the bacterial wilt situation changed J Phytopathol 163 (2015) 377–385 Ó 2014 Blackwell Verlag GmbH 377 J Phytopathol