A collaborative Ascochyta Network is launched
The production of grain legumes is limited by abiotic and biotic stresses. An important biotic stress is caused by aerial fungi of the Ascochyta genus (A. pinodes on pea, A. fabae on faba bean, A. rabiei on chickpea, A. lentis on lentil), and this leads to severe damage and yield losses in the major producing regions. To hasten the search for better control mechanisms for these ascochyta blights, expert scientists working on these diseases came together to develop a joint comparative approach for similar pathosystems, different Ascochyta species, and different aspects of the pathogen, the plant or the crop production system.
The event was the ‘First International Workshop on Ascochyta of Grain Legumes – identifying priorities for collaborative research’, held in Le Tronchet (France) on 2–6 July 2006 and it attracted 65 participants from all over the world (13 countries, especially France, Australia, USA, Canada and Spain)1.
The workshop was for a limited number of participants and the facilities combined accommodation and meeting areas. This format together with the active involvement of all participants made the workshop a success, both in terms of the high standard of scientific presentations and the friendly and fruitful exchanges. Sadly, the event was marked dramatically by the sudden death of one colleague, Bob Henson from the USA.
Four thematic sessions dealt with pathogen biology, plant resistance, epidemiology and integrated disease control, and all were reflected in the poster sessions. Two other sessions were devoted to (i) ‘thinking differently’ in order to consider inputs from non-legume or non-ascochyta experts and how the scientific results might be better exploited, and (ii) identifying priorities for joint collaboration among the legume ascochyta experts and assessing previous or current international networks.
The major presentations of this first grain legume ascochyta workshop will be published in a special issue of the European Journal of Plant Pathology. The positive discussions demonstrated the interest of the participants in maintaining this network and developing active collaborative activities.
Key highlights from the sessions
Pathogen biology
Paul Taylor (Melbourne University, Australia) presented the diagnosis methods, the origin of pathogen diversity and the method to assess this diversity, and also the contribution of genetic diversity to the pathogenicity potential. The notion of virulence was discussed and the definition of races and pathotypes was questioned.
Tobin Peever (Pullman University, USA) dealt with the notion of species among the legume ascochyta, in terms of biology (the crossing ability of isolates) and phylogeny (classifying groups according to their genetic proximity based on sequence polymorphism) leading to the highlighting of strong host specificity, even if its genetic determinants are not well known. The barriers of the crossing would be either pre or post zygotic. He questioned whether the sexual phase of Ascochyta pinodes should belong to the genus Mycosphaerella, or should possibly be linked to the genus Didymella.
For future work, the network defined three priority areas: 1) better understanding of the pathogen biology: mechanisms of infection (histopathology), the latent role of Ascochyta spp., and the role of the three pathogens of the pea anthracnose complex, 2) pathotyping with the standardised scoring and evaluation methods, using parametric (epidemiology studies and the effect on inoculum potential) and non-parametric approaches (plant breeding and the effect on yield) 3) genome sequencing.
Plant resistance
Fred Muehlbauer (USDA, USA) explained the different possible genetic controls of the resistance to ascochyta blight in different legumes (major or minor genes, dominants or recessive genes). He highlighted the impact of methodological approaches, the inoculation techniques and the resistance assessment methods on the typology of the genetic control. He also showed the possible pleiotropic effect on the plant development stages, on epidemiological development, and therefore on the resistance evaluation especially at the field level.
The network defined the following priorities for resistance: 1) links between the different results through a harmonisation of techniques for screening material, inoculation and symptoms measurements (parametric methods, exchanges of isolates, accessions and differential hosts, identifying and exchanging markers) 2) link molecular and biological data, 3) implement molecular markers in breeding and exploit tilling populations, 4) better integration of resistance into disease control management studies.
Epidemiology
Bernard Tivoli (INRA, France) showed the similarities and differences in the epidemiological development of ascochyta blights in different legume species, in terms of inoculum types, symptoms, impact on yield, pathogen survival, disease development and modelling of the disease. Discussions related to his proposals for research themes to be developed in the future were lively.
The main priorities defined for the network are: 1) histological studies of the infection process, 2) sources of inoculum (role of soil, ascospores vs. pycniospores), 3) effect of the cultural factors on epidemiological development, 4) testing and application of models in different regions and pathosystems, 5) addition of sub-modules related to ascochyta blights to existing modelling tools.
Integrated disease management
Jenny Davidson (SARDI, Australia) identified the different control methods used for fighting legume ascochyta blights: seed quality, crop rotations, agronomic management, fungicide application and plant genetic resistance. The combination of controls is of high importance and she gave the example of the fungi protection products and plant genetic resistance.
The major priorities identified are: 1) integration of knowledge on pathogen and plant phenology into agronomically sound control methods 2) more precise risk assessment, 3) develop decision-making tools and disseminate clear pragmatic messages adapted to regions.
Future collaboration
The first part of the session ‘Future collaborations’ aimed to assess the major items needing attention in the future in each area (see priorities summarised above) on the basis of the respective state of the art, and elect key priority tasks to be shared at the network level.
The second part of the session was the opportunity to exchange experience on formal or informal collaborative networks at regional or international levels: their potential and difficulties, and the possible opportunities they could provide to meet the concerns of legume ascochyta experts. It was agreed to focus on possible joint tasks or collaborations to be carried out either with existing means or with possible future financial support. Indeed the participants believe that through the respective individual programmes, some exchanges could enable the progress of each group to be optimised and the costs of activities of joint interest shared (for example, collection and screening).
A list of 15 joint priorities was defined for the interdisciplinary network. A questionnaire designed at Le Tronchet has been circulated to all participants and colleagues to assess in more detail the individual and joint interests among the group for each of these priorities.
The network participants will discuss further their collaborations and joint priorities at the Lisbon Conference in November 2007, and a second workshop ‘Ascochyta–2009’ will be organised in Pullman (USA) in Spring 2009.
1The workshop was organised by a Local Organising Committee from the joint research unit of INRA/Agrocampus BiO3P (the Biology of Organisms and Populations in relation to Plant Protection) and APBV (Plant Improvement and Biotechnologies), in collaboration with USDA (Pullman, USA), AEP (European Association for grain legume research) andthe French Society of Phytopathology (SFP), and an international Scientific Committee.
It was supported by the European Project GLIP (Grain Legumes Integrated Project), AEP, USDA, SFP, Rennes Métropole, Région Bretagne, Conseil Général, INRA ‘Département de Génétique et d'Amélioration des Plantes’, INRA ‘Mission des Relations Internationales’ and Agrocampus Rennes.
Source: B. Tivoli, F. Muehlbauer, A. Schoeny, A. Baranger, Christophe Le May, Caroline Onfroy, A. Schneider.
