May 14, 2012: Initial rust surveys in Bhutan find no trace of stem rust, but both yellow and leaf rust widespread

Cereal rust surveys were undertaken by the National Plant Protection Centre, Department of Agriculture, Ministry of Agriculture and Forest, Semtokha, Thimpu, Bhutan and the Research and Development Centre, Bajo, Wangduephodrang in collaboration with the Durable Rust Resistance in Wheat (DRRW) project during the period 17-21st April 2012. Surveys were undertaken in the wheat/barley/oat growing areas of five Dzongkhag’s in western Bhutan (Haa, Paro, Punakha, Gasa, Wangdi Phodrang). A total of 26 individual sites were visited, with several cereal fields surveyed for diseases at each location.  Surveys were conducted in agricultural areas, primarily along river valleys, at elevations ranging from 1200m to 2700m. The majority of the cereal crops surveyed were at the flowering-milk growth stage, although at higher elevations crops were observed at earlier growth stages (tillering). Berberis sp. bushes in close proximity to cereal crops and by the roadside were checked for aecial infections throughout the survey.

No stem rust was observed at any of the survey sites visited. Individual pustules with unusual morphology indicative of possible stem rust infections were collected at several sites, but subsequent microscopy at the NPPC laboratory indicated that all such pustules were actually leaf rust.

Stripe (yellow) rust was the most widespread cereal rust, being observed at 13 out of the 26 sites visited. Highest incidence and severity of stripe rust was observed in Punakha Dzongkhag. Four of the sites visited in Punakha exhibited moderate to high severity of disease. The commonly grown cultivar “Sonalika” was susceptible to stripe rust.  Both bread wheat and barley were infected with stripe rust. Low incidence and severity of stripe rust was also observed in the southern part of Paro Dzongkhag.

Leaf rust was observed at 11 out of the 26 sites visited. Distribution of the disease essentially mirrored that observed for stripe rust, with most observations occurring in Punakha Dzongkhag. Leaf rust was also recorded at two sites in Paro Dzongkhag. At all sites, except Wangdue research station, only low incidence and severity of leaf rust were recorded on the survey. The commonly grown cultivar Sonalika was considered moderately susceptible to susceptible to leaf rust.

Berberis spp. were common in the survey areas, present along roadsides and in close proximity to cereal crops. Berberis spp. infected with rust aecia were observed at three distinct locations – one location in southern Punakha (Omtekha village)  and two locations in Paro (Shabdrujedingkha and Susuna) . All infected Berberis had broad-leaf morphology, but at least two different species were considered to be susceptible to aecial infections. None of the narrow-leafed Berberis sp. examined had any signs of aecial infection.

Samples of cereal rusts (wheat stripe rust, barley stripe rust, wheat leaf rust and barley leaf rust) were collected from all infected sites. Samples of Berberis leaves infected with aecia were also collected. Samples were sent under permit to international rust laboratories in the USA, Denmark and India for subsequent race analysis.

Read full survey report – click HERE

Comments are closed.