Crop rotations with Mi gene resistant and susceptible tomato cultivars for management of root-knot nematodes in plastic houses

Four crop rotations including the Mi resistant tomato cv. Monika (R) and the susceptible cv. Durinta (S), were assessed for three consecutive cropping seasons in three unheated plastic houses located in north-eastern (Barcelona), east (Eivissa) and south-western (Cádiz) Spain. Tomatoes were cultivated from March to July 2005 (1), 2006 (2) and 2007 (3) at Barcelona and Eivissa, and from March to July 2006 (1), September 2006 to February 2007 (2) and March to July 2007 (3) at Cádiz. The crop sequences in the rotation were R1R2S3, R1S2S3 S1R2S3 and S1S2S3. Nematode population densities in soil and roots, reproduction indices, and tomato yield were compared for each cropping cycle and rotation. Average pre-plant nematode densities (Pi) at the beginning of the study were 247, 7, and 172 juveniles per 250 cm3 of soil at Barcelona, Eivissa and Cádiz, respectively. The Mi resistant tomato cv. Monika suppressed M. javanica at Barcelona and Eivissa, and M. arenaria and M. incognita at Cádiz, and prevented nematode population increases by more than 90% compared with the susceptible cv. Durinta. At Barcelona, the 3-year average tomato yield increased by 2.6 kg m−2 in the rotations including at least one resistant tomato crop, and by 6.1 kg m−2 when the resistant cultivar was cropped for two consecutive years. However, no differences in yield were found at Eivissa due to low Pi, nor at Cádiz where the resistant cultivar was poorly adapted to the agroclimatic conditions of the area.