Characterization of the <Emphasis Type="Italic">RMja</Emphasis> gene for resistance to root-knot nematodes in almond: spectrum,location, and interest for <Emphasis Type="Italic">Prunus</Emphasis> breeding |
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Authors: | Cyril Van Ghelder Bernard Lafargue Elisabeth Dirlewanger Amel Ouassa Roger Voisin Joel Polidori Marc Kleinhentz Daniel Esmenjaud |
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Institution: | 1.Equipe de Nématologie, UMR “Interactions Biotiques et Santé Végétale” (IBSV),INRA,Sophia Antipolis,France;2.Unité de Recherches sur les Espèces Fruitières (UREF), UR 419,INRA,Villenave d’Ornon,France;3.Institut National de la Protection des Végétaux,Algiers,Algeria |
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Abstract: | In Prunus spp., resistance genes to root-knot nematodes (RKN), Meloidogyne arenaria, Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne floridensis, confer either a complete spectrum, e.g., the Ma and Rjap genes in Myrobalan and Japanese plums (subgenus Prunophora), respectively, or a more restricted spectrum, e.g., the RMia gene (M. arenaria + M. incognita) in peach (subgenus Amygdalus). We report here characterization data of the RMja gene from the almond Alnem1, another Amygdalus source. The study of its spectrum is hampered by the inability of almond to be propagated by cuttings; we overcame this problem
by using F1 and BC1 crosses with previously genotyped Myrobalan plums that conferred their rooting ability to hybrids for
simultaneous evaluation to different RKN. As expected from a homozygous dominant resistance, BC1 progenies of Alnem1 segregated
for resistance to M. javanica but were uniformly susceptible to M. incognita and M. floridensis, demonstrating that RMja controlled M. javanica but not M. incognita nor M. floridensis. SSR markers covering the Prunus reference map placed RMja on LG7 in the same region as Ma and Rjap and thus showed its independence from the RMia gene (LG2) of the botanically closer peach. The spectrum of this gene allows the theoretical construction of interspecific
rootstocks, Myrobalan plum × (almond × peach), which cumulate RMja with Ma and RMia and are protected from each of the predominant RKN affecting Prunus, i.e., M. arenaria, M. incognita, and M. javanica, by at least two genes. This pyramiding strategy should offer to rootstock material an unprecedented guarantee of durable
RKN resistance. |
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