Hybrid lineage of Puccinia striiformis overlapping on wheat, barley and wild barley hosts in Uzbekistan, Central Asia.

Abstract

Stripe rust, caused by Puccinia striiformis (Ps), is a destructive disease affecting various crops worldwide, including wheat, barley, rye, triticale and certain graminaceous hosts. Recently, clonal lineages of Ps on wheat have been reported in Uzbekistan, a Central Asian region. However, it is still unclear how these clonal lineages persist throughout the year and whether they are exclusive to wheat or can also infect other hosts. To better understand, we conducted surveillance in various locations of Uzbekistan (Jizakh, Qashqadaryo, Samarkand and Sardaryo) in 2024. Site selection of barley and wild barley fields was done based on their proximity to infected wheat fields. Our results showed low genetic distance (FST) among the wheat, barley, and wild Barley Ps population. Wheat Ps populations showed the lowest genotypic diversity (Simpson' diversity =0.46) while high genotypic diversity found in barley (0.87) and wild barley (0.96). Most Multilocus genotypes that were found in barley and wild barley were confined to their respective hosts except MLG-2, which was predominant on wheat, but also infected barley and its wild relatives. MLG-2/MLG-34 was also responsible in 2023 epidemic in all wheat-growing regions of Uzbekistan and showed temporal maintenance during the 2024 cropping year. This lineage may have resulted from hybridization between Pst and Psh, though the source of parental lineages is still unknown, which requires further investigation. Monitoring the migration patterns of this lineage and estimating its pathogenic impact on overcoming different resistant genes is essential, as it has the potential to cause epidemics in both wheat and barley.