Distribution of<i>Phytophthora parasitica</i>var.<i>nicotianae</i>Races and Their Sensitivity to Metalaxyl in Georgia

Abstract

Tobacco (Nicotiana tabacum L.) samples displaying typical black shank symptoms were collected in 1990-1992 throughout the tobacco-producing area of Georgia. Cultures of Phytophthora parasitica Dastur var. nicotianae (Breda de Haan) Tucker (Ppn) isolated from samples were stored in culture until the fall of each of the years. The tobacco cultivars K 326 (low Ppn resistance), Speight G 70 (moderate Ppn resistance), Coker 371 Gold (high Ppn resistance), and the line 1071 (immune to race 0, susceptible to race 1) were grown in a greenhouse and used to determine virulence and races. Isolates were cultured on toothpicks impregnated with V8 juice agar, and the toothpicks were pushed into the stems of test plants to inoculate them