Yr5-virulent races of Puccinia striiformis f. sp. tritici possess relative parasitic fitness higher than current main predominant races and potential risk

Abstract

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive fungal diseases of wheat, and seriously threatens safe production of the crop worldwide. In China, new races historically appeared and rapidly developed to be predominant races and have resulted in ineffectiveness and replacement of wheat resistance cultivars as well as massive reduction in yield. In the present study, the relative parasitic fitness of the two newly-emerged Yr5-virulent races (TSA-6 and TSA-9) were compared with those of four currently predominant Chinese races (CYR31, CYR32, CYR33, and CYR34) based on evaluation on 10 Chinese wheat cultivars. As a result, there were significant differences in the relative parasitic fitness parameters among overall tested races based on multiple comparison (LSD) analysis (PTSA-9 (0.95)>TSA-6 (0.92)>CYR34 (0.29)>CYR31 (–1.54)>CYR33 (–1.77). The results indicated that two Yr5-virulent races TSA-9 and TSA-6 possessed relative parasitic fitness higher than races CYR34, CYR31, and CYR33, but lower than race CYR32, and have potential risks in developing to be predominant races. Therefore, continual monitoring of both Yr5-virulent races, and their variants is needed. The use of wheat cultivars (lines) with Yr5 resistance gene singly in wheat breeding is essential for being avoided, and is suggested to combine with other effective stripe rust resistance genes.

Keywords

• wheat stripe rust
• Puccinia striiformis f. sp. tritici
• parasitic fitness
• Yr5
• new race