New Puccinia triticina races on wheat in South Africa

Abstract

Virulence analysis of the South African Puccinia triticina Eriks. population from 2012 to 2016 revealed the presence of four new wheat (Triticum aestivum L.) leaf rust races, which coincided with the increased incidence of the disease during this period. Considering their infection types on 43 differential wheat entries, three of the new races namely 3SA10 (North American code CFPS), 3SA38 (CDPS) and 3SA248 (CFPS) were found to be similar to each other, and only varied in virulence for Lr20 and Lr26 whereas race 3SA115 (CBPS) was more avirulent. This was confirmed when seedling infection type data for 117 South African wheat cultivars and advanced breeding lines revealed that only 35 of the entries are susceptible to race 3SA115. Races 3SA10 (77 entries susceptible), 3SA38 (68) and 3SA248 (78) showed increased virulence when compared with the 51 entries susceptible to race 3SA145 (CCPS) which dominated in frequency during 2012 to 2016. SSR analysis confirmed the close genetic relationships between the four new races and race 3SA145. The results verified the adaptability of the leaf rust pathogen and by acquiring virulence for Lr24, the new races 3SA10, 3SA38 and 3SA248 are considered to become more prevalent and threatening compared to the current dominating race 3SA145.