Survey of barberry and associated rust pathogens in Nepal
Wheat contributes directly to food security and the national economy in Nepal. Of the rusts of wheat, stripe rust causes the most frequent and severe yield losses. Race changes can lead to damaging epidemics. To better understand factors that influence regional diversity of the stripe rust and stem rust pathogens, we surveyed rusts on barberry in 2012 and 2013. Nepal has a high diversity of barberry (30 species) and elevational habitats that extend the seasonal distributions of wheat and barberry. The greatest diversity occurs from 2,700 m and above, and distributions range from 1,200 to 4,500 m. We surveyed locations in all regions (central, eastern, western, and far-western) of the hill zone. Barberry was common between 1,300 and 1,800 m where wheat is grown. In the far-western region, barberry was found near all the wheat fields we surveyed. Between 1,300 and 1,800 m, Berberis asiatica is the most common species. B. aristata is present at the upper end of this range. Aecial infections on barberry occurred in patchy distributions in both 2012 and 2013. Collections of aecia on barberry were made at 5 locations and are being identified by inoculation studies using a range of grass hosts. Additionally, the rust samples are being evaluated by real-time PCR assays using species-specific ITS primer/probes for detection of Puccinia graminis or P. striiformis. Preliminary results for 32 single-aecia samples from 2012 were negative for P. graminis; 7 were positive for the P. striiformis complex.