QLK5-1999-01462 DREAM: Durable resistance management of the soil-borne quarantine nematode pests Meloidogyne chitwoodi and M. fallax

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Website: www.eu-dream.nl
Summary Information



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Quality of Life - 5.1.1 Sustainable Agriculture - Plant Systems

Contract No:	QLK5-1999-01462
Source:	Progress Report - January 2001 - Abstract

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Progress Report - January 2001 - Abstract

Objectives

The main aim of this project is to combat problems, in Europe, associated with the need to use highly poisonous chemicals in the control of soil-borne pests. To help reduce such use, tools and strategies for developing durable plant resistance as a means of managing some pests will be developed and disseminated. The project will use the soil-born quarentine nematodes, Meloidogyne chitwoodi and M. fallax as a model. Tools will be developed for such resistance management by developing techniques and strategies to identify durable resistance genes in host plants and (a)virulence genes in both nematodes. Rotations of the susceptible potato with resistant plants of green manure crops will be investigated as a means to optimise sustainable production systems. The durable resistance should serve as an effective and environmental sound control measure against the damaging effects of the nematodes. This will contribute to a sustainable agriculture and a healthy environment, as it will make treatment of these pests less dependent on chemicals.

Results and Milestones

Characterisation and maintenance of isolates During the first reporting year, virulent and avirulent selections of two M. chitwoodi isolates (discriminating on the wild diploid Solanum bulbocastanum genotypes) were multiplied on selected S. bulbocastanum genotypes and further propagated by partners on tomato and on potato. The material will serve as the main source of material used to investigate the interaction between avirulent and virulent nematodes and resistant hosts. For these selections, chromosome numbers have been determined. In order to characterise M. chitwoodi and M. fallax isolates at the molecular level, DNA has been extracted from approximately 50% of the total collection. Surprisingly, many of the M. chitwoodi isolates, originating from field populations, are species-mixtures.

Selection for resistance In vivo screening methods have been developed for fodder radish and Italian rye grass. A first screening of fodder radish indicated differences in M. chitwoodi development in the root. For the purpose of field testing, one M. chitwoodi infested field has been identified and many others have been investigated for a homogenous M. fallax infestation, without success so far. A screening of 15 Solanum spp. revealed resistance in 12 of them to M. chitwoodi and in 8 to M. fallax (an additional 7 have not yet been tested in relation to M. fallax). A new source for resistance in pepper to M. chitwoodi was selected and used for marker assisted breeding.

Marker assisted breeding In pepper, double haploid lines from a resistant (R) X susceptible (S) cross are available to screen for resistance to M. chitwoodi (combined with M. incognita resistance). A second RXS cross was made (resistance to M. chitwoodi and several other Meloidogyne spp.) in order to create a segregating population for gene mapping. Preliminary results suggest (in the two sources of resistance studied) a dominant monogenic inheritance of resistance. In potato, additional tests on a BC, RXS with Solanum fendleri, confirmed monogenic inheritance of resistance RMc2 to M. chitwoodi and M. fallax and linkage to a molecular marker. S. schenkii and S. sparsipilum were used in introgression programmes for resistance to M. chitwoodi and M. fallax, respectively. A diallel crossing scheme has been started between four genotypes of S. bulbocastanum, differentiating for pathotypes of M. chitwoodi.

Plant-nematode interactions and pathotypes In pepper, variety-M. Chitwoodi-isolate-interaction was found, indicating the presence of pathotypes. Double haploid lines differentiated on two discriminating M. chitwoodi isolates and M. incognita and M. hispanica isolates. One M. chitwoodi isolate was virulent to all genotypes tested so far. In potato, a virulent selection on several Solanum spp., originating from an avirulent M. chitwoodi isolate, appeared to be the first found isolate belonging to host race type 1 and to the most aggressive pathotype on S. bulbocastanum.

Histology and resistance mechanisms An in vitro culture method for the 4 target crops and infection conditions has been developed. Preliminary results of highly incompatible (HI), moderate incompatible (MI) and compatible (C) reactions of M. chitwoodi on S. bulbocastanum showed histological changes in differentiation in xylem, phloem, pericycle, and in penetration pattern in the root.

(A)virulence Crossing between M. chitwoodi isolates seems possible between individual nematodes. This is promising for further genetic studies. Genetic variability in a population was confirmed by molecular studies. This will hamper certain approaches to characterise virulence. By subtractive hybridisation between infected and non-infected tomato roots, testing DNA-sequences for search for nematode-related genes is in progress, as are studies in juveniles of virulent and avirulent isolates.

Using a different approach, thousands of expressed sequence tags from a M. incognita database and a cDNA bank have been screened resulting in a few percentage ESTs related to candidate parasitism genes. Protein electrophoresis procedures have been optimised, allowing a more sensitive and stable analysis of protein composition of virulent and avirulent isolates.

Benefits and Beneficiaries

• Knowledge on pathogenic variability in M. chitwoodi on pepper and potato (breeders, growers, extension services, scientific community)
• Sources of resistance in potato and pepper (breeders)
• Molecular marker for resistance in Solanum fendleri (breeders)
• Screening methods in all four crops (breeders)

Future Actions

The work will continue during the second year according to the planned activities in the Technical Annex with minor changes.

• The field trial for M. fallax will be replaced by a pot experiment or ring test, reflecting the absence of mono-infestation in fields
• Mono-female lines will be made for nematode crossings and possible other approaches for virulence characterisation (genetic studies hampered by large variation and way of reproduction)
• A cDNA bank of M. chitwoodi will be produced during the second year as part of a more efficiently approach.

Dissemination of results

An internet site was created for publication of non-confidential project output. Results have been made available to end users by publications, abstracts and poster presentation at different levels.