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GrainGenes Reference Report: PHY-92-38

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Reference	PHY-92-38
Title	Reaction of Ptr ToxA-insensitive wheat mutants to Pyrenophora tritici-repentis race 1
Journal	Phytopathology
Year	2002
Volume	92
Pages	38-42
Author	Friesen TL [ Show all 6 ]
Abstract	Summary: The host-selective toxin Ptr ToxA is produced by races 1 and 2 of Pyrenophora tritici-repentis, causal agent of tan spot of wheat. Ptr ToxA has been causally associated with pathogenicity by the race 2 phenotype in this system. However, the role of toxin in disease caused by race 1, the most prevalent form of the fungus in the central and northern Great Plains of North America, has not been rigorously investigated. Three independent wheat lines harboring mutations for insensitivity to Ptr ToxA were derived from ethylmethane sulfonate treatment of the hard red spring wheat cv. Kulm, possessing the single dominant gene for toxin sensitivity. Each of the three mutants was insensitive to Ptr ToxA in bioassays based on necrosis development and electrolyte leakage. Each mutant was crossed to each of the other mutants and to the wild-type Kulm. Segregation data indicate that each mutant line harbors a single recessive mutation for toxin insensitivity that maps to or near the same locus, possibly the toxin-sensitivity gene. Each toxin-insensitive mutant line was susceptible to two isolates of race 1 of P. tritici-repentis. F(2) and F(3) generations derived from crosses between Kulm and each mutant segregated for toxin reaction. However, segregation for fungal reaction was not evident, and all F(3) families were tan spot susceptible regardless of toxin reaction. Host insensitivity to Ptr ToxA is not necessarily equivalent to resistance to race 1. Ptr ToxA should not be used alone as a proxy for fungal inoculations by breeding programs aimed at developing tan spot-resistant wheat
Keyword	[ Hide all but 1 of 54 ] america bioassay breeding breeding programs causal agent cross development disease dominant dominant gene family form fungal fungus gene generation great-plains host inoculation insensitivity isolate leakage line locus maps mutant mutation necrosis necrosis toxin north america northern pathogenicity phenotype phytotoxin program ptr toxa pyrenophora pyrenophora tritici repentis race race-1 red spring wheat resistance segregation sensitivity spot spring spring wheat system tan spot toxin triticum aestivum wheat wheat mutant wild-type

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