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Low Appressorium Formation by Rust Fungi on Hordeum chilense Lines. D. Rubiales, Instituto de Agricultura Sostenible, CSIC, Apdo correos 4084, 14080 Córdoba, Spain; R. E. Niks, Plant Breeding Department, Wageningen Agricultural University, P.O. 386, 6700 AJ Wageningen, The Netherlands. Phytopathology 82:1007-1012. Accepted for publication 22 May 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1007.

There were large differences among Hordeum chilense lines in appressorium formation by the wheat and barley leaf rust fungi. The percentage of germlings producing appressoria over stomata differed from three to more than 10-fold (depending on genotype and growth stage). The differences with cultivated wheat and barley and among lines of H. chilense were most pronounced in mature plants. The low appressorium formation may be considered a case of avoidance; it was due to poor stoma recognition not to poor spore germination. This avoidance was not expressed in H. chilense × wheat amphiploids. The rate of appressorium formation was not associated with stoma frequency or size, or with number or length of leaf hairs.

Additional keywords: cereal rusts, histology, Puccinia hordei, Puccinia recondita, resistance mechanism.