Wheat yellow rust (Puccina striiformis f. sp. tritici) is currently the most damaging disease of wheat on the global scale. Under suitable conditions, yield losses of 60% or more are possible. Since 2000 two new aggressive strains of yellow rust have been identified and these have spread across continents at a rapid rate. Virulence to important resistance genes like Yr27 has appeared and has been one factor in major disease epidemics that have occurred from North Africa to South Asia.
Regularly updated situation reports on cereal rusts are given based on information provided by a global network of rust workers.
Currently, most of the global surveillance and monitoring efforts reported in RustTracker.org have focused on stem rust, but it is hoped to expand the information on yellow rust in the near future
In 2016 surveys were carried out in all the four key wheat growing regions: South Rift (June, July), Mount Kenya region (July), and North Rift (September) and Central Rift (part of August and September). A total of 304 farms were sampled. Stem rust was detected in 235(78.3%), yellow rust in twenty-eight (9.3%) and leaf rust in fourteen (4.7%) of the farms. The disease severity was ranging from trace to 90S; trace to 60S and trace to 50S for stem rust, yellow rust and leaf rust respectively. Stem and yellow rusts were detected in all the wheat growing regions while leaf was detected in South, North and Central Rift. Stem rust infection ranged from TR to 90S with maximum infection in Central Rift( 88.3%), Mt. Kenya region (80.3%); South Rift(76.5%) and North Rift (72.4%). Yellow rust infection ranged TR to 60S with maximum infection in Central Rift (16.7%); North Rift(13.3 %) and minimum infection in South Rift( 4.9%),) and Mt. Kenya region ( 1.7%). Leaf rust infection ranged from trace to 50S with maximum infection in North Rift (10.2%) minimum infection in Central Rift (3.3 %) and South Rift (1.2%). Continue reading
The latest version of the Mehtaensis newsletter (a 6 monthly newsletter named after Prof. K.C. Mehta) has just been published by the IIWBR, Regional Station, Flowerdale, Shimla. Compiled and edited by Dr. S.C. Bhardwaj, O.P. Gangwar, Pramod Prasad and Hanif Khan with technical assistance from S.B. Singh and Subodh Kumar. Mehtaensis contains a detailed summary of all the rust activities and race analysis results from India and neighbouring South Asian countries during the period July – Dec 2015. The executive summary is reproduced here:
“During offseason 135 samples of three rusts of wheat were received from Himachal Pradesh, Punjab, Tamil Nadu and Uttarakhand. 49 samples of all three rusts of wheat were analyzed, some of which were spill over of main season. Ug99 type of virulence was not identified anywhere in India. In brown rust pathotype77-5 (121R63-1) of brown rust, 46S119 and 110S119 of yellow rust and 40A (62G29) of black rust were found most frequently among the analyzed samples. Nucleus inocula of three rusts were also supplied to 38 Scientists/Research centres to facilitate research work elsewhere in India. More than 2850 lines of wheat and barley were evaluated against the pathotypes of different rusts. The tested material included the breeding lines provided by breeders from various parts of India, exotic wheat lines from CIMMYT and ICARDA. In addition 150 lines of AVT I and II are being evaluated against different pathotypes to identify rust resistant wheat lines. For monitoring the occurrence/spread of different diseases of wheat, Wheat Disease Monitoring Nursery (WDMN) and SAARC-WDMN were planted at 50 and 28 locations, respectively. Early occurrence of yellow rust was reported from Ropar, Anandpur Sahib and Hoshiarpur district of Punjab. Three Ug99 resistant genetic stocks namely FLW31, FLW32 and FLW33 have been developed. FLW31 and FLW33 are completely resistant against black and brown rusts while FLW32 has resistance to black rust and adult plant resistance against yellow and brown rusts. Work on standardization of doubled haploid production in wheat using maize pollination induced chromosome elimination was initiated. Offseason nursery was used for selection and generation advancement of 325 wheat lines. Under frontline demonstration of wheat variety, HS542 was planted in five adopted villages (12 farmers) of Tehsil Arki (Solan district of Himachal Pradesh).”
Stripe rust was detected on 18th Dec 2015 in Anandpur Sahib and Ropar districts, Punjab and subsequently in Hoshiarpur district. The variety affected was HD-2967. Following the first detection, the Indian Institute of Wheat and Barley Research (IIWBR) and other authorities are stepping up their efforts to curb the spread of the disease and urging farmers to be vigilant and take appropriate control measures. These first reports are slightly earlier than in previous years, but the locations are consistently the first places in India where stripe rust is detected. Several Indian media sources are reporting the first appearance of stripe rust in Punjab (see The Tribune, Business Standard, The Hindu, Times of India, The Tribune). As in previous years, Indian authorities are responding to these initial outbreaks in a rapid, effective and well organized way.
Favourable weather conditions for stripe rust are occurring across North Africa to South Asia. Cool, wet conditions across many parts of the region are producing a conducive environment for disease outbreaks. Aggressive races with virulence to Yr27 are known to be widely distributed in several countries and susceptible Yr27 carrying cultivars are still planted on large areas. In addition, the Warrior race (virulent on: Yr1,2,3,4,-,6,7,-,9,-,-,17,-,25,-,32,Sp,Avs,Amb) has spread into the region from Europe. Many of the resistant cultivars to the Yr27 race are likely to carry some of the genes defeated by the Warrior race, particularly in winter wheat material. After first detection in 2010, the Warrior race has spread rapidly across Europe. Most previously resistant cultivars became susceptible to this new race and widespread damage resulted in major European wheat growing areas. The Warrior race was confirmed in 2013 from Morocco, and subsequently in Algeria in 2014 (GRRC, Denmark) and Turkey in 2014 (Field Crops Research Institute, Ankara and Regional Cereal Rust Research Center, Izmir, Turkey). Under current conditions, this race is likely to spread in North Africa and the Middle East. The combined presence of the Yr27 aggressive race and the Warrior race may result in susceptibility of many existing spring and winter wheat cultivars. Although not recorded at present, acquisition of virulence for Yr27 by the Warrior race is not impossible and needs to be carefully monitored.
Serious stripe rust outbreaks are now being reported from Morocco (March 2015), and outbreaks have occurred in India (Feb 2015 http://www.tribuneindia.com/news/haryana/yellow-rust-hits-wheat-over-2000-acres-in-y-nagar/47843.html). First reports of stripe rust appearance have also been reported from south-west Iran at the end of Feb 2015. Other countries e.g., Yemen currently only have low levels of disease or are currently reported to be disease free.
Given the current and forecasted favourable weather conditions for disease development and the presence of the Yr27 aggressive race and the Warrior race, extreme caution and vigilance is advised with respect to stripe rust. Early detection, sampling, reporting and timely effective control of any outbreaks on susceptible cultivars is recommended.
Reporting of new outbreaks to Borlaug Global Rust Initiative (BGRI) staff, K. Nazari (ICARDA) firstname.lastname@example.org and D. Hodson (CIMMYT) email@example.com is encouraged. Pathotype analysis of representative samples of stripe rust would provide additional information about which sources of resistances in wheat may be at particular risk. The Global Rust Reference Centre in Denmark may undertake such analysis, but only on a limited number of samples. Please contact K Nazari or D. Hodson for essential sampling and dispatching procedures.
Following the recent release of the 2013 stripe rust report, the Global Rust Reference Center in Denmark has now just published the latest report detailing the results of race analysis for Puccinia striifromis samples submitted during the period January – December 2014. A total of 250 yellow rust infected leaf samples from 12 countries entered the recovery process using susceptible seedlings of Cartago and Morocco. A total of 83 isolates were recovered and multiplied whereas 5 isolates from Pakistan were avirulent on both Cartago and Morocco. A subset of 52 isolates from 2014 and 10 additional isolates collected in 2013 were pathotyped using an extended set of wheat differential lines carrying resistance genes to P. striiformis.
Key highlights from the report are:
- Races of the aggressive strain (likely PstS2) were common across many sampling areas in East Africa and Asia
- Aggressive strain PstS2 was detected frequently in Ethiopia, Kenya, Tanzania and Rwanda, often with additional virulence to Yr1 or Yr10
- Another group of Yr27-virulent races were observed in East Africa, e.g., Rwanda and Ethiopia
- The races in Central Asia often combined multiple virulences and many isolates produced huge amounts of telia, which may suggest a recent evolutionary origin from a sexual population
- ‘Warrior’ race was detected in Morocco and Algeria (exhibits same characteristics as above)
- Very similar races to ‘Warrior’ have been observed in Bhutan (2012) and in 2014 also in Nepal. However, these Warrior-like races from South Asia differed from the Warrior race in Europe by DNA markers and in response to additional, non-standard differentials.
A copy of the report – Hovmøller & Rodriguez-Algaba 2015: Global Rust Reference Center: Research funded by: Aarhus University,Denmark; CIMMYT; ICARDA – can be found on Wheatrust.org