Field Production, Germinability, and Survival of Puccinia striiformis f. sp. tritici Teliospores in China

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, has been recently demonstrated to be heteroecious and macrocyclic. The pathogen depends on wheat as the primary (telial) host and barberry as the main alternative (aecial) host to complete the complete life cycle. Viable teliospores are essential for the initiation of sexual reproduction of P. striiformis f. sp. tritici. However, no exact source of viable teliospores has been discovered to produce basidiospores to initiate infection on susceptible barberry. In the present study, we investigated the telial production and teliospore germinability of P. striiformis f. sp. tritici in wheat fields in Gansu and Qinghai provinces and wheat straw stacks in Qinghai in 2018 and 2019. Field production of P. striiformis f. sp. tritici teliospores was observed commonly at all growth stages of winter and spring wheat plants. The percentage of leaves bearing viable teliospores and germination rate of P. striiformis f. sp. tritici teliospores were 78.5 and 5.1% at tillering stage, 83.2 and 9.4% at early jointing stage, and 91.8 and 4.9% after booting stage in 2018 and 2019, respectively. Among wheat straw samples bearing telia collected from Qinghai province, samples with germinable teliospores ranged from 23.9% in January to 4.4% in June in 2018 and from 10.3% in January to 6.0% in May in 2019, with an overall mean germinability of 5.9%. This study showed that teliospores are produced at all growth stages of wheat under field conditions, and teliospores harbored in wheat straw stacks after wheat harvest are able to survive through winter for potential infection of barberry to the next spring.