VIRULENCE OF PUCCINIA-RECONDITA IN TEXAS FROM 1988 TO 1990

A total of 1,307 urediniospore isolates of Puccinia recondita were collected from the eight agroecological areas of wheat adaptation in Texas and characterized for virulence to a set of 14 Thatcher near-isogenic lines. Thirty-seven virulence combinations were detected. The most prevalent virulence phenotypes found were MFB-10 (virulent to Lr1, Lr3, Lr10, Lr24, and Lr26) and MDB-10 (virulent to Lr1, Lr3, Lr10, and Lr24), constituting 11 and 10% of the isolates, respectively. In all areas, virulence to Lr11, Lr24, and Lr26 increased, and virulence to Lr16 decreased. Fewer races were found in southern than in northern Texas. However, the southwest and south Texas areas had a higher proportion of isolates virulent to Lr9 and Lr30 than other areas.