VIEW ARTICLE

Resistance

Comparative Histology of Partial Resistance and the Nonhost Reaction to Leaf Rust Pathogens in Barley and Wheat Seedlings. R. E. Niks, Institute of Plant Breeding, Agricultural University, Lawickse Allee 166, 6709 DB Wageningen, the Netherlands, Present address: ICARDA, P.O. Box 5466, Aleppo, Syria; Phytopathology 73:60-64. Accepted for publication 21 May 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-60.

The histological responses involved in partial resistance (PR) and nonhost reaction were compared in three barley and three wheat genotypes inoculated with Puccinia hordei and P. recondita tritici, the leaf rust pathogens of barley and wheat. Nonhost and PR reactions to the leaf rust pathogens were characterized by a high proportion of colonies that were arrested early (ie, immediately after the formation of the first haustorial mother cells) and were associated with little or no plant cell necrosis. Eight barley genotypes, four with a low level and four with a high level of PR to P. hordei, were inoculated with the leaf rust pathogens P. hordei, P. recondita secalis, and P. recondita tritici. The latter pathogen produced reproductive structures on all four barley genotypes with a low level of PR to P. hordei, suggesting that alleles for low PR to P. hordei also reduced the effectiveness of the reaction to P. recondita tritici.