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An alternative to methyl bromide using resistant Prunus rootstocks to root-knot nematodes

Contract nr: FAIR-CT98-4139
Project nr: 4139
Project type: SC
Starting date: 01/04/1999
Duration: 48 months
Total cost: 904,400 EUR
EC Contribution: 768,400 EUR
Scientific Officer: Massimo BURIONI
Research topic: Plant health
Acronym: RKN

Prunus crops (nurseries and orchards) are severely affected under Mediterranean conditions by root-knot nematodes (RKN) Meloidogyne spp. (15% loss in vigour and yield on a worldwide basis). Because of the increase of national and international exchanges, ligneous Prunus plants from nurseries are the most common means for the dissemination of these extremely polyphagous pests. RKN are exclusively controlled by soil treatments involving the most toxic active ingredients in agriculture (fumigant: methyl bromide; non-volatile: aldicarb) that are used at high dosages and often systematically in nurseries and in intensive orchards. In stone fruits, the variety is grafted on a rootstock that can be of a different species (edible, ornamental or wild) or of an inter-specific hybrid and the potential of rootstock genetic improvement particularly for disease resistance through breeding and selection is important. Thus the use of RKN-resistant rootstocks constitutes a sound and realistic alternative to the chemical control practice for all Prunus fruit-bearing species (stone fruits: peach, almond, plum, apricot, etc.). The Ma genes from the Myrobalan plum completely suppress RKN multiplication, by conferring a complete spectrum, high and stable resistance to Meloidogyne spp. As RKN often cause wounds in Agrobacterium tumefaciens penetration, Ma genes can confer plant protection from the root crown gall, another major soil pathogen of the Prunus. Furthermore, peach sources of resistance also bear genes that can be identified, marked and pyramided with Ma genes. Simple and complex interspecific hybrids involving one or more sources and Prunus material bearing agronomic adaptation are now available.

This FAIR proposal complies with subarea 441 (plant health): the improvement of non-chemical methods (genetic resistance) for the most harmful organisms and crops requiring the heaviest treatments, and particularly more environmentally friendly alternatives to the utilisation of methyl bromide (MB). This joint effort aims at an efficient alternative to methyl bromide by incorporating RKN resistance genes into new rootstocks. Expected benefits are:
1) complete elimination of RKN soil fumigations avoiding their adverse effect on the environment;
2) clean and complete control of the nematode pest based only on natural genetic resources;
3) suppression of the nematode dissemination in agricultural soils from nurseries;
4) innovative use of bio-technologies on a perennial crop for which genetic improvement is highly time-consuming;
5) a reduction of inputs in stone fruit crop production.

This integrated approach involves five public participants (nematologists, breeders, molecular geneticists and agronomists). The proposal has two specific objectives:
1) to develop marker-aided selection (MAS) for RKN resistance genes in Myrobalan-plum and peach sources;
2) to characterise interspecific material, both for RKN resistance using MAS, and for agronomical traits.
The availability of preliminary data (RAPD markers) in the Myrobalan plum and the disposal of interspecific material to confirm the reliability of markers should provide the MAS methodology at the end of the project. Moreover, the germplasm collection and the eventual Ma-genes cloning for biotechnological applications will guarantee in the future successful incorporation of RKN resistance genes into all new rootstocks for stone fruits.

Current situation/results:
Initial results concern the genetics (INRA-IRTA-CNR) and markers (INRA-IRTA) for RKN resistance in Prunus. Two peach resistance sources (Nemared and GF.557) crossed with susceptible material are available. One F2 progeny involving Nemared segregates to M. incognita in a monogenic fashion. New F2 individuals are currently in a process of propagation or obtention to complete the numbers for further marker studies in Nemared. The other source (GF.557) is also expected to segregate to M. incognita in the tests planned in the ongoing year. In the Myrobalan plum, the detection of molecular markers has been carried out using the BSA method and one codominant SCAR marker (SCAL19) located 3-4 cM from the Ma1 gene has been elaborated. This SCAR marker appears Myrobalan-plum specific for the two genes (Ma1 and Ma3) involved in our study and can be used for marker-assisted selection of these genes in the interspecific crosses involving the peach (Nemared and GF.557) and almond (Alnem) sources.
Other current results concern the characterisation of interspecific hybrids between Myrobalan and either peach, almond, or peach-almond. This candidate rootstock material has first been evaluated for rooting capacities from herbaceous cuttings and most clones behaved quite well (INRA-SIA). All of these latter clones are now in a process of propagation for further characterisation steps. These steps are i) RKN resistance by biological tests (INRA-CNR) and MAS (using firstly SCAL19) (INRA-IRTA), ii) crown gall (INRA), iii) adaptive traits (drought, chlorosis and waterlogging) (SIA-UB).

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  • Pere ARUS
    Institut de Recerca i Tecnologia Agroalimentaries (IRTA)
    Passeig de Gracia 44
    E-08007 Barcelona
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    Unidad de Fruticultura-Servicio de Investigacion Agroalimentaria
    Depto de Agricultura y Medio Ambiente
    Diputacion General de Aragon (SIA)
    Carretera de Montanana 176
    E-50080 Zaragoza
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  • Cristos XILOYANNIS
    Universita' della Basilicata-Potenza (UP)
    Dipartimento di Produzione Vegetale
    Via Nazario Sauro 85
    I-85100 Potenza
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    Fax: +39 097 147 42 69

  • Mauro DI VITO
    Consiglio Nazionale Delle Ricerche (CNR)
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