Greenhouse Evaluation of Adult-Plant Resistance Conferred by the Gene Lr34 to Leaf Rust of Wheat. S. C. Drijepondt, Grain Crops Research Institute, Small Grain Centre, Bethlehem 9700, South Africa. Z. A. Pretorius, Grain Crops Research Institute, Small Grain Centre, Bethlehem 9700, South Africa. Plant Dis. 73:669-671. Accepted for publication 13 February 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0669.

The latent period of Puccinia recondita f. sp. tritici in flag leaves of line RL6058 (with gene Lr34) was most extended at greenhouse temperatures of 13–17 C compared with that in the leaf-rust-susceptible wheat cultivar Thatcher. A day/night regime of 25–29/13–15 C also increased latent period in RL6058, but no such differences between RL6058 and Thatcher were evident at continuous 26–30 C. Uredinia per square centimeter of flag leaf surface were fewer on RL6058 than on Thatcher. Temperature did not influence the expression of this character in RL6058, but more uredinia developed on young flag leaves than on older ones. The size of uredinia on flag leaves depended on the ambient greenhouse temperature and was more restricted at 25–29/13–15 C and continuous 13–17 C than at 26–30 C. Because of the assumed durability of Lr34 and its ability to interact with other genes to enhance the level of resistance, more deliberate exploitation of Lr34 could be justified. This study indicated that selection for Lr34 can be done in greenhouses with adequate temperature control.

Keyword(s): resistance components.