RESEARCH REPORTS                                                             TGC REPORT 52, 2002 ______________________________________________________________________                             Introgression    of    resistance    against    Mi-1-virulent    Meloidogyne    spp.    from Lycopersicon peruvianum into L. esculentum 1 Moretti, A., 2 Bongiovanni, M., 2 Castagnone-Sereno, P., 1 Caranta, C. 1 INRA, Genetics and Breeding of Fruits and Vegetable, Dom. St Maurice, BP94, 84143 Montfavet cedex, France. E-mail : caranta@avignon.inra.fr 2 INRA,  Interactions  Plantes  Micro-organismes  et  Santé  Végétale,  123  Boulevard  F. Meilland, BP 2078, 06606 Antibes cedex, France. E-mail : pca@antibes.inra.fr Root-knot  nematodes  (Meloidogyne  spp.)  are  one  of  the  main  pathogens  of tomato crops worldwide. Up to now, all tomato cultivars with resistance to Meloidogyne originated  from  a  single  resistant  L.  peruvianum  interspecific  F1  plant  carrying  the dominant gene  Mi-1 (Smith, 1944).  Mi-1 is effective against  M. incognita,  M. arenaria and  M.  javanica  but  there  have  been  several  reports  of  field  or  laboratory-selected isolates   from   the   three   species   able   to   reproduce   on   tomato   plants   with   Mi-1 (Castagnone-Sereno  et  al.,  2001).  Moreover,  the  need  for  introgression  of  additional resistance  genes  against  root-knot  nematodes  increased  with  the  prohibition  of  the nematicide methyl bromide, from 2005 in all the European Union.   Among  the  resistance  sources  and  genes  against  nematodes  available  in  wild tomato  species,  the  Mi-3  gene  from  L.  peruvianum  family  VWP2x4  is  of  particular interest since it is effective against M. incognita strains virulent on Mi-1 and also confers resistance at 32°C (Yaghoobi et al., 1995). Seeds from the L. peruvianum family VWP2x4 homozygous for Mi-3 (based on DNA  marker  NR14)  were  kindly  provided  by  V.  Williamson  (Univ.  California,  Davis, USA).  This  material  was  also  homozygous  for  Mi-1  as  indicated  by  the  DNA  marker REX-1. Five plants VWP2x4 homozygous for both Mi-3 and Mi-1 were hybridized with L. esculentum Momor sp. (an INRA near isogenic line in the Moneymaker type containing the Ve, Frl and Tm-22 resistance genes and the sp gene, Laterrot, 1996) used as the female parent. Buds were emasculated and immediately pollinated with pollen from L. peruvianum; the same buds were pollinated at least two other times at 2-days intervals. Fruits were harvested 30-32 days after. The 371 fruits obtained presented 0 to 3 seeds per fruit; among them, a single one presented an immature embryo. Classical embryo rescue technique leads to a single F1 hybrid plant (Smith, 1944). Cuttings  of  the  interspecific  F1  hybrid  were  evaluated  for  resistance  against  M. incognita, M. arenaria, M. javanica using both Mi-1-avirulent and Mi-1-virulent isolates and also against M. hapla (not controlled by Mi-1) during two independent tests (Table 1).  Resistance  evaluation  was  performed  as  described  in  Castagnone-Sereno  et  al. (2001) and the behavior of the interspecific F1 hybrid was compared with those of the L. esculentum Saint Pierre (susceptible to Meloidogyne spp.) and Piersol (homozygous for Mi-1).   As expected, L. esculentum Saint Pierre is highly susceptible to all strains of M. incognita, arenaria, javanica and hapla. L. esculentum Piersol is resistant only against M. incognita Antibes, M. arenaria Marmande and M. javanica Avignon ; this resistance spectrum results from the presence of Mi-1. On the contrary, the Mi-1-virulent isolates reproduce  well  on  Piersol.  Both  the  parental  line  L.  peruvianum  VWP2x4  and  the 21

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