Host Status of Alfalfa Cultivars and Germ Plasms to Meloidogyne chitwoodi Race 2 and Reactions of Selected Cultivars to M. chitwoodi and M. hapla Infection. H. Mojtahedi, Research Associates, Washington State University, College of Agriculture and Home Economics, Prosser 99350. J. N. Pinkerton, G. S. Santo, and R. N. Peaden. Research Associates, Professor, Washington State University, College of Agriculture and Home Economics, Prosser 99350, and Research Agronomist, U.S. Department of Agriculture, Agricultural Research Service, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350. Plant Dis. 73:391-394. Accepted for publication 3 January 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-73-0391.

The reproductive efficiency of Meloidogyne chitwoodi race 2 was evaluated on 50 alfalfa cultivars and germ plasms. The reproductive factor (final egg density at 55 days ÷ 5,000 [initial egg density]) ranged from 1.1 to 40. An experimental line, W12SR2W1, consistently exhibited a high degree of resistance to M. chitwoodi race 2. Reproduction of M. chitwoodi race 2 and M. hapla on W12SR2W1 was between alfalfa cultivars Lahontan and Nevada Synthetic XX, susceptible and resistant to M. hapla, respectively. The pathogenicity of M. chitwoodi race 2 and M. hapla on selected commercially grown alfalfa cultivars was less clear. They reduced the number of plants per pot of cv. WL-312 alfalfa without affecting its shoot or root growth and temporarily reduced the shoot dry weight of cv. Vernal alfalfa. M. chitwoodi race 2 increased cv. Thor alfalfa shoot and root growth and had no adverse effect except to decrease leaf area. M. hapla did not alter the shoot or root growth of Thor alfalfa.