Wheat yellow rust
Introduction Yellow rust distribution in winter triticale '''Wheat yellow rust''' ('''''Puccinia striiformis'' f.sp. ''tritici'''''), also known as '''wheat stripe rust''', is one of the three major wheat rust diseases, along with stem rust of wheat (''Puccinia graminis'' f.sp. tritici) and leaf rust (''Puccinia triticina'' f.sp. tritici).
History As R.P. Singh, J. Huerta-Espino, and A.P. Roelfs say in their 2002 comprehensive review of literature on the wheat rusts for UN FAO:Although Gadd first described stripe rust of wheat in 1777, it was not until 1896 that Eriksson and Henning (1896) showed that stripe rust resulted from a separate pathogen, which they named ''P. glumarum''. In 1953, Hylander et al. (1953) revived the name ''P. striiformis''.A stripe rust outbreak in northwest Syria contributed to the beginning of the Syrian Civil War by increasing food prices.
Life cycle Other cereal rust fungi have macrocyclic, heteroecious life cycles, involving five spore stages and two phylogenetically unrelated hosts. ''P. striiformis'' was thought to be microcyclic for centuries until 2009, when a team of scientists at the USDA-ARS Cereal Disease Lab led by Yue Jin confirmed that barberry (''Berberis'' and ''Mahonia'' spp.) is an alternate host. Barberry was known as an alternate host of the closely related stem rust (''Puccinia graminis'') and for many years, when infection was observed on barberry, it was assumed to be stem rust. (Then ''P. striiformis'' was accidentally discovered to ''also'' have the same alternate host when scientists observed rust infection on various barberry species, and inoculated spores of this unknown rust onto Poaceae hosts. Kentucky Bluegrass was the only one to show infection. The uredinia were characteristic of stripe rust.) Later, infected wheat plants bearing teliospores were soaked in water and suspended over barberry species. Infection was produced, thus solving a "century-old mystery" of plant pathology. This finding is regarded as revolutionary across the discipline and additionally among mycologists.
Symptoms Stripe rust on wheatYellow rust, or stripe rust, takes its name from the appearance of yellow-colored stripes produced parallel along the venations of each leaf blade. These yellow stripes are actually characteristic of uredinia that produce yellow-colored urediniospores. Primary hosts of yellow rust of wheat are ''Triticum aestivum'' (bread wheat), ''Triticum turgidum'' (durum wheat), triticale, and a few ''Hordeum vulgare'' (barley) cultivars.The disease usually occurs early in the growth season, when temperature ranges between ; but it may occur to a maximum of . High humidity and rainfall are favorable conditions for increasing the infection on both leaf blade and leaf sheath, even on spikes when in epidemic form. Symptoms are stunted and weakened plants, shriveled grains, fewer spikes, loss in number of grains per spike and grain weight. Losses can be 50%, but in severe situations 100% is vulnerable. Since yellow rust can occur whenever the wheat plants in green and the environmental condition conducive for the spore infection, yellow rust is a severe problem in the wheat-producing regions worldwide. Temperatures during the time of winter wheat emergence and the coldest period of the year are crucial for epidemic development in winter-habit wheat crops.
Worldwide population structure Both the spatial genetic structure and the spatial dissemination of this disease have been investigated. Population genetic analyses indicate a strong regional heterogeneity in levels of recombination, with clear signatures of recombination in the Himalayan and near-Himalayan regions and a predominant clonal population structure in other regions. The existence of a high genotypic diversity, recombinant population structure, high sexual reproduction ability, and the abundance of the alternate host (''Berberis'' spp.) in the Himalayan and neighboring regions suggest the region as a plausible ''Pst'' center of origin or at least very close to its centre of origin. However, further exploration may be useful from Central Asia to East Asian regions.
Disease management Breeding of resistant varieties is the most cost-effective method to control this rust. Fungicides are available but vary in availability depending on their registration restrictions by national or state governments. Development of varieties resistant to the disease is always an important objective in wheat breeding programs for crop improvement. This has been done in the past, however as normal, these resistance genes became ineffective due to the acquisition of virulence to that particular resistance gene rendering the variety susceptible - necessitating ongoing variety development.===Resistance genes===These genes are most often abbreviated ''Yr'' and ''Yr1'', ''Yr24'', etc. is a quantitative trait locus (QTL) for adult plant resistance (APR). This allele comes from the . Bouvet ''et al. '', 2021 discovered it when investigating unknown resistance in the UK 2015 and 2016 seasons. It has since broken down however.====Lebanon====Although ''Yr6'', ''Yr7'', ''Yr8'', ''Yr9'', ''Yr10'', ''Yr17'', ''Yr24'', ''Yr25'', and ''Yr27'' are no longer effective in Lebanon, ''Yr1'', ''Yr3'', ''Yr4'', ''Yr5'', ''Yr15'' are still effective against yellow rust pathotypes prevalent there.
See also *''Puccinia striiformis'' var. ''striiformis''
References *Ali S. (2012) Population biology and invasion history of Puccinia striiformis f.sp. tritici at worldwide and local scale, Ph.D. dissertation. Université Paris-Sud 11. *Chen, X. M.  2005.Epidemiology and control of stripe rust Puccinia striiformis f. sp. tritici on wheat. Can. J. Plant Pathol. 27:314-337. *Doodson, J.K., Manners, J.G. and Myers, A. (1964). Some effects of yellow rust (''Puccinia striiformis'') on the growth and yield of spring wheat. Ann. Bot. 28: 459–472. *Eriksson, J. and E. Henning. 1896.Die Getreideroste. Ihre Geschichte und Natur sowie Massregein gegen dieselben. P. A. Norstedt and Soner, Stockholm. 463 pp. *Hogg, W.H., Hounam, C.E., Malik, A.K., and Zadoks, J.C. 1969.Meteorological factors affecting the epidemiology of wheat rusts. WMO Tech Note 99.143 pp. *Hovmøller, M. S., Sørensen, C. K., Walter, S., Justesen, A. F. (2011) Diversity of Puccinia striiformis on cereals and grasses. Annual Review of Phytopathology 49, 197–217. *Hylander, N., I. Jorstad and J.A. Nannfeldt. 1953.Enumeratio uredionearum Scandinavicarum. Opera Bot. 1:1-102. *Jin, Y., Szabo, L.J., and Carson, M.  2010.Century-old mystery of Puccinia striiformis life history solved with the identification of Berberis as an alternate host. Phytopathology 100:432-435. *Poehlman J.M. and D.A. Sleper. 1995.Breeding Field Crops. 4th Ed. Iowa State Press/Ames, Iowa 50014. *Robbelen, G. and Sharp, E. L., 1978.Mode of inheritance, interaction and application of genes conditioning resistance to yellow rust. Adv. Plant Breeding, 9, 88 pp. *Saari, E. E. and Prescott, J. M., 1985.World distribution in relation to economic losses. Pages 259–298, in: The Cereal Rusts Vol. II: Diseases, distribution, epidemiology and control, A. P. Roelfs and W. R. Bushnell eds., Academic Press, Orlando, Fl. *Stubbs, R. W., 1985.Stripe rust. Pages 61–101 in: The Cereal Rusts Vol. II: Diseases, distribution, epidemiology and control, A. P. Roelfs and W. R. Bushnell eds., Academic Press, Orlando, Fl. Zadoks, J. C. and Bouwman, J. J., 1985.Epidemiology in Europe. Pages 329–369 in: The Cereal Rusts Volume II: Diseases, distribution, epidemiology and control, A. P. Roelfs and W. R. Bushnell eds., Academic Press, Orlando, Fl.
External links *http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Publications/CerealRusts/The%20Cereal%20Rusts_VOLUME%20II.pdf*http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Cerealrusts/stripe_rust_control.pdf*http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Cerealrusts/Pst-life-cycle%20Phyto-reprint.pdf*http://www.cimmyt.org*http://www.ars.usda.gov/Main/site_main.htm?modecode=36-40-05-00*