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Disease Note.

A New Host Raceof Meloidogyne chitwoodi from California. H. Mojtahedi, Washington State University, Irrigated Agriculture Research and Extension Center (IAREC) Prosser, WA 99350. G. S. Santo, Washington State University, Irrigated Agriculture Research and Extension Center (IAREC), and C. R. Brown, USDA-ARS, IAREC, Prosser, WA 99350 and H. Ferris and V. Williamson, Department of Nematology, University of California, Davis 95616. Plant Dis. 78:1010. Accepted for publication 27 June 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1010E.

Meloidogyne chitwoodi Golden et al consists of two host races. Race 1 does not reproduce (reproductive factor [RF): final number of eggs x initial inoculum of 5,000 eggs per pot < 0.1) on Thor alfalfa, and race 2 does (RF > 1) (2). Both races cause serious damage to potato, but neither reproduces (RF < 0.1) on clonal selection PI275187.10 of Solanum bulbocastanum Dun., a wild potato species used as a source of resistance in our breeding program (1). Fourteen field isolates of M. chitwoodi collected from a potato production area in the Pacific Northwest failed to reproduce (RF < 0.1) on S. bulbocastanum. However, an isolate from Tulelake, California, (CAMC2) reproduced (RF = 7 and 11) on S. bulbocastanum in two greenhouse experiments. Esterase enzyme pattern and RF of CAMC2 on Columbian tomato, 51 Stephens wheat, 36 Florunner peanut, 0 NC95 tobacco, 0.01 California Wonder pepper, 0.01 Charleston Gray watermelon, 0.3 and Deltapine cotton, 0, were typical of M. chitwoodi races 1 and 2. However, CAMC2 was more similar to race 2, in that Thor alfalfa was a suitable host (RF = 12). This host race of M. chitwoodi, which reproduces on resistant S. bulbocastanum, was designated race 3.

References: (1) C. R. Brown et al. Plant Dis. 73:957, 1989. (2) Cl. S. Santo et al. Plant Dis. 69:361. 1985.