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Elongation of Secondary Hyphae of Erysiphe graminis f. sp. tritici on Wheat with Compatible and Incompatible Parasite/Host Genotypes. Richard E. Stuckey, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; Albert H. Ellingboe, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 64:530-533. Accepted for publication 31 October 1973. DOI: 10.1094/Phyto-64-530.

The lengths of secondary hyphae of Erysiphe graminis f. sp. tritici 20-30 h after inoculation varies with the genotype of host and parasite. With a compatible parasite/host genotype (Px/pmx), or the incompatible genotype (P2/Pm2) that does not affect primary infection, secondary hyphae elongate at about 2-3 µm/h. Secondary hyphae that become longer than 10 µm with the incompatible genotype, P3a/Pm3a, continue to elongate the first 26 h at the same rate as hyphae with the compatible genotype. Secondary hyphae that begin to elongate on the incompatible genotypes, P1/Pm1 and P4/Pm4, cease elongation at about 26 and 22 h after inoculation, respectively.