ug99 is a lineage of wheat stem rust ( puccinia graminis f. sp. tritici ) , which is present in wheat fields in several countries in africa and the middle east and is predicted to spread rapidly through these regions and possibly further afield , potentially causing a wheat production disaster that would affect food security worldwide .

it can cause up to 100 % crop losses and is virulent against many resistance genes which have previously protected wheat against stem rust .

although ug99-resistant varieties of wheat do exist , a screen of 200 000 wheat varieties used in 22 african and asian countries found that only 5-10 % of the area of wheat grown in these countries consisted of varieties with adequate resistance .

the original race of ug99 , which is designated as ' ttksk ' under the north american nomenclature system , was first characterised in uganda in 1999 ( hence the name ug99 ) and has since been detected in kenya , ethiopia , eritrea , sudan , yemen , iran , uganda , tanzania , mozambique , zimbabwe , south africa , and egypt .

there are now 11 known races of ug99 .

they are all closely related and are believed to have evolved from a common ancestor , but differ in their virulence/avirulence profiles and the countries in which they have been detected .

ug99

ug99 has since spread to 13 countries and there are 13 variants of the ug99 race of stem rust .
resistance to stem rust ug99 in six bread wheat cultivars maps to chromosome 6ds .
identification and evaluation of sources of resistance to stem rust race ug99 in wheat .
identification of wheat gene sr35 that confers resistance to ug99 stem rust race group .
genes , encodes resistance to wheat stem rust race ug99 . science 341 : 786–788
but those who dismissed ug99 as a mere anomaly would soon be proven dreadfully wrong .
the emergence of ug99 races of the stem rust fungus is a threat to world wheat production .
riding the winds , ug99 has breached the best defenses science can offer . photo : gallery stock
resistance to stem rust ug99 in six bread wheat cultivars maps to chromosome 6ds . - pubmed - ncbi
if you suspect you have seen ug99 in cereal crops , take a photo and record the location .
identification of wheat gene sr35 that confers resistance to ug99 stem rust race group . - pubmed - ncbi
rust tracker : cimmyt and bgri provides a google earth visualization that tracks ug99 status world - wide .
symptoms of wheat rust ug99 on the leaves ( source : r . l croissant , bugwood . org )
the good news is that canadian breeders have spent the last 18 years building ug99 resistance into some wheat varieties .
einkorn wheat researchers used for identifying the sr35 gene that is resistant to the ug99 strain of wheat stem rust .
ars scientists developed a sensitive diagnostic method to accurately determine whether or not stem rust symptoms are caused by any of the highly virulent strains of the pathogen in the ug99 fungus family . if wheat plants suspected of harboring ug99 stem rust are found in the united states , aphis will use this diagnostic method to determine whether or not ug99 is present .
the emergence of ug99 races of the stem rust fungus is a threat to world wheat production . - pubmed - ncbi
molecular mapping and validation of srnd643 : a new wheat gene for resistance to the stem rust pathogen ug99 race group .
identification of markers linked to the race ug99 effective stem rust resistance gene sr28 in wheat ( triticum aestivum l . ) .
india is the world’s second largest wheat producer behind china . pakistan ranks ninth . both countries grow varieties that are susceptible to ug99 .
ars home » midwest area » st . paul , minnesota » cereal disease lab » docs » ug99 - emerging virulent stem rust races
rust pathogens change rapidly , often by mutation . six additional variants are now recognized in the ug99 lineage . all exhibit an identical dna fingerprint , but differ in virulence patterns . additional important resistance genes e . g . , sr24 & sr36 have now been defeated by variants of ug99 . ug99 or variants are considered a major threat to wheat production with an estimated 80 - 90 % of global wheat cultivars susceptible .
molecular mapping and validation of srnd643 : a new wheat gene for resistance to the stem rust pathogen ug99 race group . - pubmed - ncbi
the leverage ( tv series ) of 27 june 2010 ( usa ) aired an episode called
the inside job
that had part of its storyline the introduction of ug99 into the world ' s wheat system to cause destruction of the world supply except for ug99 resistant strains .
egypt is the most recent country where the ug99 race was detected in 2014 . it is now found all along the east coast of africa .
ars released a hard white winter wheat with resistance to the wheat stem rust ( ug99 ) pathogen—protecting this crop from this devastating disease . ars scientists screened more than 1300 wild relatives of wheat in the ars germplasm collection and discovered critically needed new sources of ug99 resistance in wheat . [ more ]
be aware of any ug99 biosecurity measures that may be in place for incoming goods and conveyances . industry advice notices are reviewed regularly and could change .
ug99 workshop summary summary of national workshop on new virulences in wheat and barley stem rust held march 5 - 6 , 2008 , in baltimore , maryland .
the team ' s study ,
identification of wheat gene sr35 that confers resistance to ug99 stem rust race group ,
appears in the journal science .
fetch said the most plausible explanation why ug99 has yet to appear in india and pakistan is that it has been dry in that region prior to this year .
in australia if stem rust is detected on any wheat lines that were thought to be resistant to wheat stem rust , they need to be tested for ug99 .
if you receive or work around goods imported from overseas , including mail , you need to be vigilant to stem rust symptoms from ug99 and other exotic pests .
next , researchers isolated the candidate gene and used biotechnical approaches to develop transgenic plants that carried the sr35 gene and showed resistance to the ug99 race of stem rust .
ug99 is spreading slower than scientists anticipated but it is only a matter of time before it wipes out crops in some of the world’s most important wheat - growing regions .
hiebert cw , fetch tg , zegeye t ( 2010 ) genetics and mapping of stem rust resistance to ug99 in the wheat cultivar webster . theor appl genet 121 : 65–69
rouse mn , wanyera r , njau p , jin y ( 2011 ) sources of resistance to stem rust race ug99 in spring wheat germplasm . plant dis 95 : 762–766
wheat stem rust has largely been under control for over three decades due to the widespread use of resistant cultivars . in 1999 , a new virulent race of stem rust was identified from wheat fields in uganda – popularly known as ug99 after the year and country of discovery . using north american scientific nomenclature , ug99 is known as race ttksk . ug99 ( race ttksk ) is a cause for concern as it exhibits unique virulence patterns . no other race of stem rust has been observed to overcome so many wheat resistance genes , including the very important gene sr31 . by 2007 , ug99 ( race ttksk ) had spread via wind movements out of east africa , into yemen and as far as iran .
first , the bad news . the spread of ug99 ( a lineage of wheat stem rust ) across eastern africa and western asia is slow but steady , and new strains continue to appear . there is general consensus that ug99 will eventually arrive in north america . “in addition , ” says tom fetch jr . , “a resistance gene that was effective against ug99 and most other races of stem rust called srtmp , which has been widely used in winter wheat breeding and some spring wheat breeding , has recently lost its efficacy . ”
in 2005 , hodson was asked to develop a model for predicting the spread of ug99 based on global wind patterns . the climactic data he gathered suggested that airborne particles from yemen would inevitably alight in iran or iraq . and sure enough , in 2007 and then in 2009 iran endured successive ug99 infections , suggesting that a full - blown epidemic is possible .
tom fetch , a stem rust specialist in cereal crops with agriculture canada , works with global partners to fight the spread of ug99 , a race of stem rust spreading across africa . fetch studies ug99 in a new facility at the ag canada research centre in morden , man . , which is the only level 3 lab in canada designed for hazardous plant pathogens . | file photo
the wheat stem rust spores are carried by the wind across continents . ug99 first appeared in uganda and quickly spread to kenya and ethiopia last year ; both countries suffered serious crop yield losses in 2007 .
some wheat varieties are resistant to ug99 , but they represent just 10 percent of the varieties grown around the world . and even these plants are not necessarily immune to infection . ug99 continues to mutate and spread , and new virulent races , or biotypes , of the fungus that are able to skirt plant resistance strategies could emerge at any time . just last year , for example , outbreaks of a novel stem rust race in ethiopia and germany infected ug99 - resistant wheat plants . in the oft - repeated words of the late wheat - breeding pioneer norman borlaug of the rockefeller foundation and cimmyt , “rust never sleeps . ”
that’s why the usda has suddenly become so alarmed over ug99 and why szabo now finds himself a very busy ( and well - funded ) scientist . armed with banks of high - speed polymerase chain reaction machines , he’s in the midst of a two - year project to sequence the ug99 genome . he hopes to identify the pathogen’s effector genes — the genes that actually do the dirty work of destroying wheat . if these genes can be cloned and inserted into bacteria that will produce the corresponding proteins , then new breeds of wheat could be screened for ug99 resistance in a lab , eliminating the need to ship them to njoro for exposure in the wild .
recently , ug99 , a particularly devastating strain of wheat stem rust fungus , has emerged , which could potentially threaten food security . now , two genes have been cloned that offer resistance to ug99 . saintenac et al . ( p . 783 , published online 27 june ) cloned sr35 from triticum monococcum , a diploid wheat species not often cultivated . periyannan et al . ( p . 786 , published online 27 june ) cloned sr33 from aegilops tauschii , a diploid wild grass that contributed to the hexaploid genome of cultivated wheat . the genes both encode proteins that show features typical of other disease resistance proteins and offer opportunities to slow the pace of ug99 progression .
ug99 pathotype of puccinia graminis is a fungal pest causing wheat stem rust that poses a high biosecurity risk to the wheat industry . it could cause total crop failure to australia’s economically important cereals wheat , barley , oats and rye .
wind is the most common cause of ug99 dissemination . the spores are picked up and blown long distances , causing the disease to move incrementally across adjacent countries and has been documented to traverse oceans . “if it gets to china , that would be very concerning , ” fetch notes . “we know there have been events where dust particles have blown across from china to north america , and a rust spore is equal to or even lighter in weight compared to these particles . ” there is also another way ug99 could turn up in north america – and that’s through human transfer . “rust spores can be transported on clothes , ” fetch says . “this is how stripe rust was introduced into australia . we don’t know how likely it is or how soon ug99 could be introduced into north america in this manner , but the more ug99 spreads , the greater the chance that someone – or wind currents – could bring it over here . ”
ug99 is a race of stem rust first discovered in uganda in 1999 . its discovery jarred wheat breeders around the world because it is virulent to sr31 , a stem rust resistance gene that was widely used in international wheat breeding programs .
most wheat researchers and breeders agree that to protect plants from ug99 , they must develop wheat varieties with several rust - resistance genes , so that if the fungus mutates to outwit one defense , there are others there to take on the pathogen . the problem is that it can take years to achieve this goal using traditional breeding methods . in the meantime , favorable winds could spread ug99 even farther , and the fungus continues to evolve resistance to wheat crops’ natural defenses .
indeed , 90 percent of the world’s wheat has little or no protection against the ug99 race of p . graminis . if nothing is done to slow the pathogen , famines could soon become the norm — from the red sea to the mongolian steppe — as ug99 annihilates a crop that provides a third of our calories . china and india , the world’s biggest wheat consumers , will once again face the threat of mass starvation , especially among their rural poor . the situation will be particularly grim in pakistan and afghanistan , two nations that rely heavily on wheat for sustenance and are in no position to bear added woe . their fragile governments may not be able to survive the onslaught of ug99 and its attendant turmoil .
if you see symptoms of stem rust from ug99 or anything unusual , report it to the exotic plant pest hotline 1800 084 881 . this will put you in touch with the department of primary industries or agriculture in your state or territory .
due to the widespread susceptibility to ug99 and the potential perspectives of new widespread stem rust epidemics , the global rust initiative ( urltoken ) set as one of its top priorities the monitoring and deployment of new sources of resistance to stem rust .
citation : yu l - x , chao s , singh rp , sorrells me ( 2017 ) identification and validation of single nucleotide polymorphic markers linked to ug99 stem rust resistance in spring wheat . plos one 12 ( 2 ) : e0171963 . urltoken
the sr35 gene was one of those genes that was discovered in einkorn wheat grown in turkey ,
akhunov said .
until now , however , we did not know what kind of gene confers resistance to ug99 in this wheat accession .
yu lx , barbier h , rouse mn , singh s , singh rp , bhavani s , et al . ( 2014 ) a consensus map for ug99 stem rust resistance loci in wheat . theor appl genet . 127 : 1561–81 . pmid : 24903979
iran is of particular concern in terms of ug99’s spread , because of a common native shrub called the barberry which is susceptible to stem rust . ug99 normally reproduces asexually , releasing billions of spores that are mostly clonal , although mutation to new strains occurs frequently . however , if the barberry bush gets infected , sexual reproduction of ug99 with other stem rust strains already present can occur . this allows genetic recombination of virulence genes from both parents , with the possible development of offspring with different traits than either parent and a high potential for new virulent strains to appear . fetch has recently begun collaborating with scientists marcia chavez and jose martinelli in brazil , as barberry is native to that country as well . they have just begun identifying the types of rust that infect barberry there .
ug99 stem rust was discovered in uganda in 1999 ( hence the name ug99 ) and is now present in 13 countries , with rwanda and egypt being the newest ones in which it’s been detected . three new strains have appeared over the last few years , which brings the current total to 10 . the disease is characterized by the presence of brick red , elongated , blister - like pustules that often lead to the death of the plant . towards the end of the growing season , black spores are produced which overwinter and later can infect the alternate host ( barberry shrub ) in the spring . it’s estimated that 80 to 90 per cent of global wheat varieties are susceptible to the ug99 strains . the strains are unique in their ability to attack the sr31 gene , which was the only one protecting many of the world’s wheat cultivars .
genetic engineering would also make it easier to pull in genes from wild relatives , a rich source of ug99 resistance , without dragging along potentially unappealing agronomic qualities . ( see “wild relatives , ” the scientist , june 2014 . ) “we’re looking at germ plasm , old varieties , [ and ] wild relatives [ for resistance genes ] , ” says maricelis acevedo , a wheat researcher at north dakota state university who has identified a ug99 resistance gene , called srwlr , in an old wheat variety grown in iran . 5 “there’s so much diversity there that has not been utilized . ”
to identify the resistance gene sr35 , the team turned to einkorn wheat that is known to be resistant to the ug99 fungal strain . einkorn wheat has limited economic value and is cultivated in small areas of the mediterranean region . it has been replaced by higher yielding pasta and bread wheat varieties .
this is the usda’s cereal disease laboratory , where 30 , 000 enemies of wheat , barley , and oats are held captive so their malevolent secrets can be learned . and among these pathogens are numerous samples of ug99 , sent here from nations already infiltrated by the new strain of p . graminis .
basnet br , singh s , lopez - vera ee , huerta - espino j , bhavani s , jin y , et al . ( 2015 ) molecular mapping and validation of srnd643 : a new wheat gene for resistance to the stem rust pathogen ug99 race group . phytopath . 105 : 470–6 .
the good news , fetch notes , is that he and his colleagues at the aafc cereal research centre understand the disease quite well and are achieving success using genes in combination to create multi - gene stacks of resistance . indeed , over the years , aafc has invested over $ 14 million to develop new resistant wheat varieties and fund other related ug99 work . “we’ve identified three new genes , we’re identifying molecular markers , and we’re examining other sources of resistance , ” fetch explains . “we also receive isolates from kenya and eritrea and test them to see whether it’s a new ug99 strain or something else . ”
hiebert cw , fetch tg , zegeye t , thomas jb , somers dj , humphreys dg , mccallum bd , cloutier s , singh d , knott d ( 2011 ) genetics and mapping of seedling resistance to ug99 stem rust in canadian wheat cultivars ‘peace’ and ‘ac cadillac’ . theor appl genet 122 : 143–149
additional markers with unknown chromosomal positions were also identified with ug99 resistance . for instance , based on the ld analysis , among five unknowns , four markers , jd _ c6624 _ 7769357 , rfl _ contig2671 _ 2362005 , jd _ c1314 _ 1888758 and cap7 _ c2912 _ 1387634 were tightly linked to the sr25 locus , a major effective gene against the ug99 lineage ( fig 3 ) . two of them ( jd _ c6624 _ 7769357 and cap7 _ c2912 _ 1387634 ) were later confirmed by the kasp assay where 90 and 95 % cosegregation with sr25 phenotypes were obtained , respectively ( table 4 ) .
“there it is , ug99 , ” says brian steffenson , a plant pathologist at the university of minnesota , as he taps the glass to point out the dark - red fungus flecking the leaves of the young plants . as they grow , their stems will form large pustules of the fungus that will go on to shed pathogenic spores . ug99 is a strain of wheat stem rust that was first identified in uganda in 1998 ( and named in 1999 ) . by 2001 , ug99 began appearing in fields in kenya ; in ethiopia by 2003 ; sudan and yemen by 2006 ; and iran a year later . it now plagues wheat plants in nine african and middle eastern countries . should the pathogen establish a global presence , 90 percent of wheat varieties could succumb , with whole crops flopping over and rotting within weeks or months of infection . the annual global harvest of some 700 million tons of wheat would be decimated .
researchers have identified a gene that gives wheat plants resistance to one of the most deadly races of the wheat stem rust pathogen , called ug99 . the discovery may help scientists develop new wheat varieties and strategies that protect the world ' s food crops against the wheat stem rust pathogen that is spreading from africa .
although molecular markers have been used for marker - assisted selection ( mas ) for wheat stem rust resistance , most of them are gel - based markers using fragment size comparison ( urltoken ) . it is time consuming and laborious . the single nucleotide polymorphic ( snp ) marker is the marker of choice for mas because of their high abundance , widespread distribution throughout the genome , and their potential for high - throughput genotyping . in the present study , we first applied genome - wide association studies ( gwas ) to identify snp makers linked to ug99 stem rust resistance loci in wheat lines developed at cimmyt using the wheat 9k iselect snp chip . we then used a high throughput assay named kompetitive allele specific pcr ( kasp ) for validating significant markers closely linked to the ug99 resistance loci . our goal was to develop a robust and high throughput platform that can be used in mas for breeding wheat cultivars with improved resistance against ug99 stem rust .
a number of pathotypes of wheat stem rust are already present in australia , and resistant wheat varieties have been developed for those . unfortunately , ug99 has overcome many wheat resistance genes , and can attack all parts of the plant that are above ground . however , stem and leafs are most impacted by the fungus .
pathotype ug99 of stem wheat rust is a production pest and will also affect leaves and grain . if you work around imported goods , you need to look for grain that is infected with reddish brown , powdery pustules . also ensure that all imported agricultural machinery is clean and free of wheat seeds and other contaminants .
singh rp , hodson dp , huerta - espino j , jin y , bhavani s , njau p , herrera - foessel s , singh pk , singh s , govindan v ( 2011 ) the emergence of ug99 races of the stem rust fungus is a threat to world wheat production . annu rev phytopathol 49 : 465–481
after the winter session , the cdl puts its ug99 in suspended animation , so the pathogen can be reanalyzed for years to come . for the other p . graminis samples , many of which date back to the 1950s , this is done by placing vials of spores together in vats filled with liquid nitrogen . but ug99 is accorded special treatment : its spores are sealed in a dedicated freezer set to - 112 degrees fahrenheit . solitary confinement is necessary to prevent a careless researcher from unleashing the enemy . “we wouldn’t want someone to mistakenly grab the wrong tube out of the liquid nitrogen , ” says les szabo , a research geneticist at the cdl .
newcomb m , acevedo m , bockelman he , brown - guedira g , goates b , jackson ew , jin y , njau pn , rouse mn , singh d , wanyera r , bonman m ( 2013 ) field resistance to the ug99 race group of the stem rust pathogen in spring wheat landraces . plant dis 97 : 882–890
using the microsatellite method , szabo needs only 48 hours to determine whether a p . graminis sample is ug99 . but given what’s at stake for us wheat , he wants to ensure that precious days aren’t wasted in sending samples to and from st . paul . so he’s developing a 24 - hour dna test called a taqman pcr , which can be used by regional pathology labs that regularly analyze infected wheat . the faster a ug99 invasion can be detected , the better the odds of containing its damage : fungicides can be applied immediately . ( however , due to their expense , scarcity , and negative environmental impact , such fungicides are considered only a stopgap measure . )
until that point , wheat breeders had two or three genes that were so efficient against stem rust for decades that this disease wasn ' t the biggest concern ,
akhunov said .
however , the discovery of the ug99 race of pathogen showed that changes in the virulence of existing pathogen races can become a huge problem .
1993 : there is some evidence that race ttksk may have been present in kenya . 1998 : severe stem rust infections observed in uganda . ug99 identified , characterised as having virulence on sr31 and named . 2000 : ttksf detected in south africa . 2001 : ttksk detected in kenya . 2003 : ttksk detected in ethiopia . 2006 : ttksk detected in sudan and yemen . ttkst , a new variant of ug99 with virulence to sr24 , detected in kenya . 2007 : tttsk detected in kenya . ttksp detected in south africa . ptksk detected in ethiopia . ptkst detected in ethiopia . 2008 : fao announced the presence of ug99 in iran . ptkst detected in kenya . 2009 : ttksk detected in tanzania . ttkst detected in tanzania . tttsk detected in tanzania . ttksf detected in zimbabwe . ptksk detected in kenya . ptkst detected in south africa . 2010 : ttkst detected in eritrea . ptkst detected in eritrea . ptkst detected in mozambique . ptkst detected in zimbabwe . ttksf + detected in south africa . ttksf + detected in zimbabwe .
but hodson is suspicious of just how predictable ug99 has been so far . “maybe one of the most surprising things for me is that we haven’t yet seen a random jump , a very long - distance jump , ” he says . in rare instances , fungal spores have been known to ride the winds across oceans — a sugarcane rust that first appeared in florida in 1978 , for example , is thought to have blown in from cameroon . hodson’s greater fear is that ug99 will spread via the “747 route” — hitching rides on human travelers . this is how yellow rust first got to australia in 1979 , tucked into the clothing of a farmer who had vacationed in the french countryside .
of markers identified in the present study , 10 were mapped and they were located on two homoeologous groups ( groups 4 and 7 ) based on the 9k consensus map [ 12 ] . on group 4 , marker ex _ c1373 _ 2628597 located on 4a is in the same region where the temporarily designated gene , srnd643 , was mapped [ 15 ] . this gene was identified from wheat breeding line ‘nd643 / 2 * webill1 ( or wbll1 ) ’ , and is effective against the ug99 group races at both seedling and adult growth stages . “wbll1” was also present based on pedigree in a number of wheat lines used in this study . therefore , the marker ex _ c1373 _ 2628597 is likely to identify the same gene as srnd643 . marker ex _ c30581 _ 39482788 on 4b shared the same chromosome location with sr37 , a gene that is effective against the ug99 lineage . sr37 was originally transferred from wild triticum timopheevii var . araraticum [ 5 ] but was not successfully utilized in wheat breeding . of significant markers on 7b , marker ex _ c43096 _ 49510164 located at the position ( 65 cm ) where no ug99 resistance gene has been reported , although sr17 was mapped in the same region , it is ineffective against ug99 [ 7 ] . on the other hand , marker ex _ c12556 _ 19992307 identified on 7bl 163 . 9 cm ) overlapped with the location of the stem rust resistance qtl reported by bansal et al . [ 16 ] . moreover , we identified a dart marker associated with stem rust resistance in the same region in our previous study [ 10 ] . the consistent identification of loci associated with stem rust resistance in this region suggests that there is likely a novel sr gene on 7bl contributing to ug99 resistance .
diagnostic markers for sr25 reported in this study can facilitate mas for ug99 resistance in wheat since sr25 is effective against races of the ug99 lineage [ 1 , 8 , 23 ] . in the present study , four snp markers were found to be closely linked to sr25 and were able to predict wheat lines carrying sr25 with marker cap7 _ c2912 _ 1387634 having the highest accuracy ( 95 % ) ( table 4 ) . the other two markers , ex _ c5884 _ 10325223 and jd _ c6624 _ 7769357 were able to detect sr25 - cariers at 86 and 90 % accuracies , respectively ( table 4 ) , while marker ra _ c25242 _ 34807178 had the lowest accuracy ( 78 % ) .
singh rp , hodson dp , jin y , huerta - espino j , kinyua mg , wanyera r , et al . ( 2006 ) current status , likely migration and strategies to mitigate the threat to wheat production from race ug99 ( ttks ) of stem rust pathogen . cab rev perspect agric vet sci nutr nat resour 1 ( 054 ) : 13
there is no single gene that has helped diamondbird escape the worst of ug99’s punishment . the plant is protected instead by a combination of so - called minor genes , which work in tandem to slow the enemy rather than stop it cold . this pragmatic approach to engineering resistance is now much in vogue among breeders keen to make p . graminis irrelevant once more .
1 . y . jin et al . , “detection of virulence to resistance gene sr24 within race ttks of puccinia graminis f . sp . tritici , ” plant disease , 92 : 923 - 26 , 2008 . 2 . y . jin et al . , “detection of virulence to resistance gene sr36 within the ttks race lineage of puccinia graminis f . sp . tritici , ” plant disease , 93 : 367 - 70 , 2009 . 3 . s . periyannan et al . , “the gene sr33 , an ortholog of barley mla genes , encodes resistance to wheat stem rust race ug99 , ” science , 341 : 786 - 88 , 2013 . 4 . c . saintenac et al . , “identification of wheat gene sr35 that confers resistance to ug99 stem rust race group , ” science , 341 : 783 - 86 , 2013 . 5 . j . d . zurn et al . , “high - density mapping of a resistance gene to ug99 from the iranian landrace pi 626573 , ” molecular breeding , doi : 10 . 1007 / s11032 - 014 - 0081 - 8 , 2014 .
wheat stem rust is caused by a fungal pathogen . according to akhunov , since the 1950s wheat breeders have been able to develop wheat varieties that are largely resistant to this pathogen . however , the emergence of strain ug99 in uganda in 1999 devastated crops and has spread to kenya , ethiopia , sudan and yemen , though has yet to reach the u . s .
singh rp , hodson dp , huerta - espino j , jin y , bhavani s , njau p , et al . ( 2011 ) the emergence of ug99 races of the stem rust fungus is a threat to world wheat production . in : van alfen nk , bruening g , leach je ( eds ) annual review of phytopathology , vol 49 . palo alto , pp 465–481 .
he and his fellow scientists around the world are scrambling to halt the pathogen . to do so , they must figure out a way to reach deep within the wheat genome and create genetic barriers that ug99 cannot overcome . and they must do so quickly , before the pestilence moves on to the next continent , and then the one after that — wreaking havoc on the world’s food supply .
there are other wheat rust diseases that have similar symptoms to ug99 . these include : leaf rust ( puccinia triticina ) which causes small brown circular pustules that are normally on the upper leaf surface , but can also be on the wheat sheath in severe epidemics ; and stripe rust ( puccinia striiformis f . sp . tritici ) characterised by long stripes of small yellowish orange pustules on the leaves .
since it was discovered a dozen years ago , ug99 has steadily crept north and east out of uganda . wind patterns could soon carry it to the punjab region on the border of india and pakistan — one of asia’s most crucial breadbaskets . in the next few years , the pathogen could also travel through iran to afghanistan , as well as into turkey . — b . i . k .
wagoire , 55 , was once a wheat breeder of some renown , having studied at the university of cambridge and apprenticed under the late norman borlaug , a nobel - laureate agronomist who revolutionized modern farming . but even though he hasn’t worked full - time on wheat for years , wagoire will forever have a place in cereal lore as the man who discovered the ug99 race of p . graminis .
the resulting genotypic and phenotypic data were used for gwas to identify markers associated with ug99 resistance in the 5 th srrsn ( fig 2a ) . the relative positions near the known sr genes were indicated at the top of the respective chromosomes . fig 2b illustrated the quantile - quantile plot ( qq ) using observed against expected p - values . using a cutoff fdr rate of 0 . 05 , 12 significant markers were detected ( fig 2a above the dotted line , table 2 ) . among them , seven were located on four chromosomes based on the consensus map constructed by cavanagh et al . [ 12 ] . marker ex _ c1373 _ 2628597 on chromosomes 4a was located at the position of the previously reported stem resistance gene , srnd643 [ 15 ] . similarly , marker ex _ c30581 _ 39482788 on chromosome 4b overlapped with the location of sr37 [ 7 ] . on chromosome 7b , one marker ( ex _ c43096 _ 49510164 ) was located where no ug99 - effective genes have been reported . although sr17 was located on 7bs , it was reported to be ineffective to the ug99 lineage [ 7 ] . another marker ex _ c12556 _ 19992307 was identified on 7bl in the same region where a qtl for stem rust resistance has been reported [ 16 ] . on 7d , a marker , ex _ c2123 _ 3988735 was located on the short arm and coincided with the ug99 resistance gene srta100171 [ 17 ] . the other two , ex _ c5884 _ 10325223 and ra _ c25242 _ 34807178 were located on 7dl and overlapped with the location of sr25 / sr43 .
race ttksk ( ug99 ) was the first known race of p . graminis f . sp . tritici with virulence to the stem rust resistance gene sr31 . it also possesses virulence to a wide range of resistance genes of wheat origin , plus others of alien origin . the pathogen is changing rapidly and thirteen known variants have been identified within the ug99 lineage of wheat stem rust . the ug99 race group is present in 13 countries , with egypt being the most recent country in which the ug99 race group was detected ( see map ) . the latest variants are : ttksf + , detected in south africa and zimbabwe from samples collected in 2010 ( pretorius et al . 2012 ) ; tthst ( collected in kenya 2013 , newcomb et al in prep ) ; ttktt , ttktk . ptktk and tthsk ( patpour et al 2015 , fetch et al . , 2016 ) – all collected in kenya in 2014 . all variants are considered to be single step mutations . acquired virulence to additional important sr genes , notably sr24 and sr36 , is known from kenya ( sr24 , sr36 ) , egypt ( sr24 ) , eritrea ( sr24 ) , ethiopia ( sr24 , sr36 ) , mozambique ( sr24 ) , rwanda ( sr36 , sr24 ) , south africa ( sr24 ) , tanzania ( sr24 , sr36 ) , uganda ( sr24 , sr36 ) and zimbabwe ( sr24 ) . race ttkst , carrying combined sr31 + sr24 virulence , caused epidemics in kenya in 2007 . ug99 races carrying combined sr31 + sr24 virulence are spreading rapidly throughout africa and it is considered likely that they will spread further in the future . in addition , virulence to the srtmp gene has now been acquired by the latest variants detected in kenya ( i . e . , race ttktt , race ttktk , and race ptktk ) . at least one of these variants ( ttktk ) appears to spreading rapidly , also being detected in 2014 in egypt , eritrea , rwanda and uganda ( patpour et al . , 2015 ) .
the green revolution defeated stem rust by relying on single “major” genes like sr31 and sr24 , which bestowed near - blanket immunity to p . graminis . “but the thing about major genes is that they either work or they don’t — it’s black or white , ” bariana says . so once ug99 started beating the majors , the vast majority of the world’s wheat immediately lost protection and became completely vulnerable .
wheat stem rust , caused by puccinia graminis f . sp . tritici ( pgt ) , is a devastating disease that can cause severe yield losses . a previously uncharacterized pgt race , designated ug99 , has overcome most of the widely used resistance genes and is threatening major wheat production areas . here , we demonstrate that the sr35 gene from triticum monococcum is a coiled - coil , nucleotide - binding , leucine - rich repeat gene that confers near immunity to ug99 and related races . this gene is absent in the a - genome diploid donor and in polyploid wheat but is effective when transferred from t . monococcum to polyploid wheat . the cloning of sr35 opens the door to the use of biotechnological approaches to control this devastating disease and to analyses of the molecular interactions that define the wheat - rust pathosystem .
wheat stem rust , caused by puccinia graminis f . sp . tritici ( pgt ) , is a devastating disease that can cause severe yield losses . a previously uncharacterized pgt race , designated ug99 , has overcome most of the widely used resistance genes and is threatening major wheat production areas . here , we demonstrate that the sr35 gene from triticum monococcum is a coiled - coil , nucleotide - binding , leucine - rich repeat gene that confers near immunity to ug99 and related races . this gene is absent in the a - genome diploid donor and in polyploid wheat but is effective when transferred from t . monococcum to polyploid wheat . the cloning of sr35 opens the door to the use of biotechnological approaches to control this devastating disease and to analyses of the molecular interactions that define the wheat - rust pathosystem .
at the university of minnesota , steffenson is on a similar mission , traveling the world over to find traits in wild grasses that might be beneficial to farmers . he brings plants back to st . paul and raises them in grow rooms just around the corner from the cereal disease laboratory’s biosafety greenhouse where researchers experiment with ug99 . one room contains rows of goatgrasses ( aegilop s sp . ) , unremarkable - looking plants with a stunning ability to resist rust infection . in his analysis of one species , aegilops sharonensis , steffenson found that 82 percent of the samples were resistant to ug99 ; 97 percent of plants of another species , aegilops longissima , were resistant ; and all samples of a third species , aegilops speltoides , remained healthy despite rust exposure . “when you look at what wild crop relatives can contribute to cultivated species , it’s just a phenomenal amount of allelic diversity , ” he says . despite such enviable resistance , aegilops grasses make terrible food crops . “we call it ‘the model nonmodel organism , ’” says the sainsbury laboratory’s wulff , who is working with steffenson to understand how goatgrasses resist ug99 infection . the goal is to isolate those defenses and bring them into wheat , while leaving behind aegilops’ less desirable agronomic traits .
initially , many african farmers turned to wheat that included the resistance gene sr24 to protect their crops from infection , but by 2006 , yue jin of the cdl and his colleagues identified a new variety of ug99 in kenya that could sidestep the defense . 1 then , in 2007 , jin and his colleagues found that yet another valuable resistance gene , sr36 , had also succumbed to the rapidly evolving fungus . 2
this spread to the islamic republic tracks neatly with what hodson terms “route a , ” the likeliest scenario for ug99’s migration . if his model continues to hold , the pathogen should steadily move toward the punjab over the next few years — almost an exact repeat of the migratory path taken by a novel form of yellow rust , which was first detected in kenya in 1986 , then arrived in india a decade later .
stem rust has been uncommon in wheat and barley in canada for over 60 years , because wheat breeders and pathologists have ensured varieties with good resistance were produced . albert tenuta , ontario ministry of agriculture , food and rural affairs ( omafra ) field crop pathologist , stresses that although a lot of attention is put on ug99 , there is also the possibility that a new stem rust race could develop here in north america .
genes that are currently effective against ug99 are displayed on by clicking on the map below ( opens in a new page , requires javascript enabled ) . if you cannot see the map , the links on the left panel will take you to gene specific pages within maswheat . it must be noted that the resistance genes confer different levels of protection and the most effective strategy is to stack several on the same genetic background .
stem rust is one of the most devastating diseases affecting wheat worldwide . in north america the last epidemics were recorded in 1955 , since then stem rust has been under control by the use of resistant cultivars and eradication of alternate hosts . resistant cultivars have always been effective control of this disease worldwide . but in 1999 a new race of puccinia graminis f . sp . tritici , the causative agent of stem rust , was detected in uganda that was virulent against the traditional wheat resistance genes , sr31 and sr38 ( 1 ) . this race was denominated ttks , or alternatively , ug99 . in 2003 race ug99 was found in kenya and in 2007 in yemen ( 1 - 3 ) . this virulent race could soon migrate to the middle east and central asia and can attack many of the current cultivars in use worldwide ( 4 , 5 ) .
it is expected that more varieties with this two - gene resistance stack will be released by aafc in the near future . “as with most crop breeding , it’s a multi - year process , ” fetch notes . “for several years before he recently retired , dr . doug brown at aafc in winnipeg developed many crosses with the ‘cadillac’ resistance to ug99 , so a lot of his work will bear fruit in the coming years . ”
the pathogen has already been detected in iran and may now be headed for south asia’s most important breadbasket , the punjab , which nourishes hundreds of millions of indians and pakistanis . what’s more , ug99 could easily make the transoceanic leap to the united states . all it would take is for a single spore , barely bigger than a red blood cell , to latch onto the shirt of an oblivious traveler . the toll from that would be ruinous ; the us department of agriculture estimates that more than 40 million acres of wheat would be at serious risk if ug99 came to these shores , where the grain is the third most valuable crop , trailing only corn and soybeans . the economic loss might easily exceed $ 10 billion ; a simple loaf of bread could become a luxury . “if this stuff gets into the western hemisphere , ” steffenson says , “god help us . ”
cimmyt’s singh was one of the first to become aware of ug99 when it emerged in uganda , and right from the beginning , he says , it raised big concerns . what was especially alarming to him at the time was that many rust - resistant cimmyt varieties , developed with the traits borlaug introduced , were vulnerable to the new race . “even from 1998 , it was clear we would have trouble sooner or later , ” he says .
5 . current status , likely migration and strategies to mitigate the threat to wheat production from race ug99 ( ttks ) of stem rust pathogen . singh rp , hodson dp , jin y , huerta - espino j , kinyua mg , wanyera r , njau p , ward rw . in : cab reviews : perspectives in agriculture , veterinary science , nutrition and natural resources , 2006 , 1 , no . 054 doi : 10 . 1079 / pavsnnr20061054
a more durable way to protect wheat against ug99 would be to insert multiple rust resistance genes in a single variety of wheat—a process called pyramiding or stacking , and a technique that helped borlaug’s wheat varieties withstand rust’s attack for so long . in particular , researchers are looking to stack multiple “major” or “seedling” resistance genes , which defend the plant against a specific pathogen at all stages of the host’s growth . ( see illustration . ) “the goal is to provide cultivars with more than one [ ug99 ] resistance gene , hopefully three , ” says rouse at the cdl . “it might slow down the virulence . ” the stacking of major resistance genes can also be done in tandem with pyramiding “adult” resistance genes . these confer only partial resistance to an infection , but in combination can offer good protection against multiple strains of rust and are remarkably durable , often lasting for decades before being overcome by fungal mutations .
grain yield and protein content tend to be a higher priority for growers than pathogen resistance , anderson says . to develop a resistant strain that is appealing to growers , breeders must select for all of these qualities . as a result , “progress is still very slow to have a full scope of resistance [ to ug99 ] , ” says jin . “breeders are moving toward that , but they can’t put all of their resources into a single strain of disease . ”
pyramiding of more effective rust resistance genes into wheat cultivars with common background using rust bioassays is challenging due to the lack of isolates with specific avirulence / virulence gene combinations for assigning resistance genotypes . this is particularly true for broadly effective genes [ 8 , 9 ] . furthermore , field bioassays for the ug99 lineage can only be conducted in regions where they are already present . high throughput diagnostic markers closely linked to stem rust resistance loci are needed to facilitate selection of desirable genotype combinations .
traditionally , breeders have introduced resistance traits into crops by crossing commercial plants with other wheat varieties or related taxa that are able to fend off a pathogen . using this method , borlaug successfully bred stem rust–resistant plants that thwarted other races of the once - devastating pathogen for four decades . ( see
wheat whisperer , circa 1953 .
) then , in 1998 , scientists detected ug99 , a race of stem rust that had finally found a way around the crop’s main rust defenses .
two new races of the wheat ( triticum aestivum l . ) stem rust pathogen , representing the fifth and sixth variants described within the ug99 lineage , were detected in south africa . races ttksp and ptkst ( north american notation ) were detected in 2007 and 2009 , respectively . except for sr24 virulence , race ttksp is phenotypically identical to ttksf , a commonly detected race of puccinia graminis f . sp . tritici ( pgt ) in south africa . ptkst is similar to ttksp except that it produces a lower infection type on the sr21 differential and has virulence for sr31 . simple sequence repeat ( ssr ) analysis confirmed the genetic relationship amongst ttksf , ttksp , ptkst and ttksk ( ug99 ) . ttksk , ptkst and ttksf grouped together with 99 % similarity , while sharing 88 % genetic resemblance with ttksp . these four races in turn shared only 31 % similarity with other south african races . it is proposed that ttksp arose locally as a single step mutation from race ttksf , whereas ptkst probably represents an exotic introduction of pgt to south africa .
current status , likely migrations and strategies to mitigate the threat to wheat production from race ug99 ( ttks ) of stem rust pathogen . singh , r . p . , hodson , d . p . , jin , y . , huerta - espino , j . kinyua , m . g . , wanyera , r . , njau , p . and ward , r . w . cab reviews : perspectives in agriculture , veterinary science , nutrition and natural resources , 2006 , 1 , no . 054 , 13 pp .
identified ssr markers ( xcfd49 and xbarc183 ) linked with stem rust resistance for efficient use in marker - assisted selection and stacking of resistance genes in wheat breeding programs . more than 80 % of the worldwide wheat ( triticum aestivum l . ) area is currently sown with varieties susceptible to the ug99 race group of stem rust fungus . however , wheat lines niini , tinkio , coni , pfunye , blouk , and ripper have demonstrated ug99 resistance at the seedling and adult plant stages . we mapped stem rust resistance in populations derived from crosses of a susceptible parent with each of the resistant lines . the segregation of resistance in each population indicated the presence of a single gene . the resistance gene in niini mapped to short arm of chromosome 6d and was flanked by ssr markers xcfd49 at distances of 3 . 9 cm proximal and xbarc183 8 . 4 cm distal , respectively . the chromosome location of this resistance was validated in three other populations : pbw343 / coni , pbw343 / tinkio , and cacuke / pfunye . resistance initially postulated to be conferred by the srtmp gene in blouk and ripper was also linked to xcfd49 and xbarc183 on 6ds , but it was mapped proximal to xbarc183 at a similar position to previously mapped genes sr42 and srcad . based on the variation in diagnostic marker alleles , it is possible that niini and pfunye may carry different resistance genes / alleles . further studies are needed to determine the allelic relationships between various genes located on chromosome arm 6ds . our results provide valuable molecular marker and genetic information for developing ug99 resistant wheat varieties in diverse germplasm and using these markers to tag the resistance genes in wheat breeding .


trochomorpha kuesteri is a species of air-breathing land snail , a terrestrial pulmonate gastropod mollusk in the family trochomorphidae .

this species is endemic to micronesia .

trochomorpha kuesteri

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here you will find one or more explanations in english for the word kuesteri . also in the bottom left of the page several parts of wikipedia pages related to the word kuesteri and , of course , kuesteri synonyms and on the right images related to the word kuesteri .
genus : trochomorpha j . a . albers , 1850 ( db : 53 sp )
trochomorpha apia ( j . b . hombron & c . h . jacquinot , 1852 )
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thank you for taking the time to provide feedback on the iucn red list of threatened species website , we are grateful for your input .
gland , switzerland , 5 july 2018 ( iucn ) – australia’s unique reptiles – including lizards and snakes – face severe threats from invasive species and climate change , with 7 % of th . . .
the value of medicinal and aromatic plant trade has increased three - fold in the past 20 years , but traditional harvesting practices are being replaced by less sustainable alternatives . . . .
a recently released iucn technical brief recommends increasing investments in sustainable land management practices , as well as better cooperation between agriculturalists and conservationists to conse . . .
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genus : bertia c . m . f . ancey , 1887 ( db : 2 sp )
subgenus : bertia ( exrhysota ) f . c . baker , 1941 ( db : 1 sp )
bertia ( exrhysota ) brookei ( a . adams & l . a . reeve , 1848 )
genus : brazieria c . m . f . ancey , 1887 ( db : 6 sp )
brazieria entomostoma ( j . b . hombron & c . h . jacquinot )
genus : coxia c . m . f . ancey , 1887 ( db : 1 sp )
genus : hogolua f . c . baker , 1941 ( db : 1 sp )
genus : kondoa f . c . baker , 1941 ( db : 3 sp )
genus : trochositala a . a . schileyko , 2002 ( db : 1 sp )
genus : videna h . adams & a . adams , 1855 ( db : 28 sp )
genus : vitrinoconus j . o . semper , 1873 ( db : 2 sp )
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