Morphology and AFLP markers suggest three Hordeum chilense ecotypes that differ in avoidance to rust fungi M. Carlota Vaz Patto, Aernoudt Aardse, Jaap Buntjer, Diego Rubiales, Antonio Martín, and Rients E. Niks Abstract: In Hordeum chilense Roem. & Schult., a high variation in the level of avoidance to infection of barley leaf rust (Puccinia hordei Otth) occurs. Probably resulting from the properties of the stomata, the rust germ tube overgrows stomata, and the infection process fails in an early stage. In the present study we tested the hypothesis that the avoid- ance character occurs in certain morphologically and molecularly distinct ecotypes of H. chilense. Eighty-eight H. chilense accessions were inoculated with P. hordei to assess the level of avoidance. The accessions were described for 30 morphological characters and three AFLP primer combinations. Cluster analysis using both morphological and AFLP fingerprint data suggested three distinct clusters of accessions. One of the clusters had a particularly high level of avoidance. This putative subspecific taxon was characterized by shorter and wider spikes, more erect culms, a greater number of stomata per square centimetre on the abaxial leaf side, and a shorter uppermost internode until flag leaf. All accessions clustered in this subspecific taxon were collected from humid habitats. We conclude that H. chilense consists of at least three rather well defined, morphologically and genetically distinct subspecific taxa, one of which has a very high level of avoidance to barley leaf rust. Key words: AFLP fingerprinting, diversity, Hordeum chilense, avoidance, rust fungi, Puccinia hordei. Résumé : Chez l’Hordeum chilense Roem. & Schult., on observe une forte variation de la capacité à éviter l’infection par la rouille naine des feuilles (Puccinia hordei Otth). Résultant probablement de propriétés des stomates, le tube ger- minatif des rouilles pousse au dessus des stomates et le processus d’infection avorte très tôt. Les auteurs ont vérifié l’hypothèse que le capacité d’évitement se retrouverait chez certains écotypes morphologiquement ou moléculairement distincts, de l’H. chilense. Ils ont inoculé 88 accessions de l’H. chilense avec le P. hordei afin dévaluer le degré d’évitement. Ils ont décrit ces accessions en combinant 30 caractères morphologiques et trois amorces AFLP. L’analyse par regroupement, en utilisant à la fois les empreintes AFLP et la morphologie, suggèrent l’existence de trois regroupe- ments parmi les accessions. Un des regroupements montre un degré particulièrement élevé d’évitement. Ils ont caracté- risé ce présumé taxon sub-spécifique sur la base d’épillets plus courts et plus larges, de chaumes plus droits, d’un nombre plus élevé de stomates/cm 2 sur la face foliaire abaxiale, et d’un entre-noeud supérieur plus court jusqu’au stade de l’étendard. Toutes les accessions regroupées dans ce taxon sub-spécifique proviennent d’habitats humides. Les au- teurs concluent que l’H. chilense est constitué d’au moins trois taxons sub-spécifiques bien définis, ainsi que morpholo- giquement et génétiquement distincts, dont un montre un forte capacité à éviter la rouille naine des feuilles. Mots clés : AFLP, empreinte, diversité, Hordeum chilense, évitement, rouille fongique, Puccinia hordei. [Traduit par la Rédaction] Vaz Patto et al. 213 Introduction Hordeum chilense Roem. & Schult. is a diploid perennial wild barley (2n = 14), included in the section Anisolepis Nevski of the genus Hordeum in the Triticeae tribe. Hordeum chilense is confined to the zone of central Chile and the most western parts of the provinces of Neuquen and Rio Negro in Argentina, where it is found along roadsides, in pastures, and in mesic, as well as xeric habitats and at al- titudes up to 2100 m (Tobes et al. 1995; Giménez et al. 1997). The species shows a very wide range of variation of morphological characters (von Bothmer et al. 1980, 1995) and is mainly autogamous (Martín et al. 1998). Hordeum chilense is readily crossed with wheat, rye, and also cultivated barley (Martín and Chapman 1977; Martín and Cubero 1981; Martín et al. 1996), allowing the possible transfer of traits to cultivated cereals. One of the characters for which large variation has been found is the degree to which germ tubes of rust pathogens overgrow the stomata and fail to penetrate into the leaf tissue (Rubiales and Niks 1992a, 1996). This trait is considered a case of avoidance (Rubiales and Niks 1992a). Avoidance mechanisms of plants reduce the probability of intimate con- Can. J. Bot. 79: 204–213 (2001) © 2001 NRC Canada 204 DOI: 10.1139/cjb-79-2-204 Received June 2, 2000. Published on the NRC Research Press website on February 13, 2001. M.C. Vaz Patto, A. Aardse, J. Buntjer, and R.E. Niks. 1 Laboratory of Plant Breeding, Wageningen University, PO Box 386, 6700 AJ Wageningen, The Netherlands. D. Rubiales and A. Martín. Instituto de Agricultura Sostenible (CSIC), Apdo 4084, 14080 Córdoba, Spain. 1 Corresponding author (e-mail: rients.niks@pv.dpw.wau.nl).