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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Notes: With regard to the other rust fungi occurring on maize, Puccinia sorghi can be distinguished from P. polysora (see CMI Descript. 4) by the larger, usually more sparse and elongated uredia; the regular, well rounded, darker urediospores, the black open telia, and the well rounded teliospores, with thicker apical walls and long pedicels, and from Physopella zeae (see CMI Descript. 5) which has hyaline urediospores and covered telia containing sessile teliospores (see Cummins, Phytopathology 31: 856-857, 1941). Maize rust increased in prevalence and severity during the 1950's in the central states of the U.S.A. on both dent and sweet corn hybrids. A contributing factor was the gradual substitution of the numerous open pollinated maize varieties by hybrids of limited genetic constitution during the previous two decades, which led to an increase in susceptibility to the pathogen. This event stimulated search for sources of genes for rust resistance, notably the joint studies at Iowa State College and the University of Wisconsin (36: 466, 583; 38: 365). Mexican maize appears to be one of the best sources of rust resistance, which occurs in two types, protoplasmic and mature plant (35: 291). For investigations on the inheritance of resistance and other genetical studies see 41: 302, 386, 453 and595 and for the effect of various physiological factors on pathogenicity see 39: 227.Rust resistant maize varieties have also been successful in reducing disease losses in Guatemala (33: 598),Transvaal (35: 588), Texas (33: 217), and New South Wales (36: 455).Attempts to control rust disease in the field in Malaya and Colombia using copper fungicides have not beensuccessful owing to phytotoxic effects (33: 524; 35: 166). Sulphur has also been found ineffective in Mexico (31:371) but the following fungicides gave some control: Dithane in Florida (31: 13), Fermate in Mexico (31: 371) andBlitane in Nyasaland (34: 145). Greenhouse tests of fungicides at Michigan, U.S.A., showed good control whensodium and copper omadine and panogen 15 were applied as foliar sprays (37: 13). 
Description type:Non-original description 
Description:Puccinia sorghi Schwein., Trans. Amer. phil. Soc. ser. 2, 4: 295, 1832.
= Puccinia maydis Berenger, 1845.
= Puccinia zeae Berenger, 1851.
= Aecidium oxalidis Thuem., 1876.
= Tumletia epiphylla Berk. & Broome, 1882.
= Dicaeoma sorghi (Schwein.) Kuntze, 1898.
Pycnia up to about 6 on each side of the leaf, grouped on an area up to 0,5 mm diam. in the centre of the spot. Aecia onunderside of leaf only, surrounding the pycnia in a zone up to 2 mm wide, cupulate, 0,15-0,2 mm diam. Aeciospores sphericalor ellipsoidal, 15-24 µm diam.; wall hyaline, verrucose, 1-2 µm thick. Uredia on both sides of leaves and leaf sheaths, dense or sparse, irregularly scattered, circular and about 1 mm. diam. or elongated and up to about 10 mm.long. Urediospores spherical or ellipsoidal, 24-29 x 22-29 µm; wall amber, minutely echinulate, 1,5-2 µm thick; pores 3-4, equatorial. Telia like the uredia but black. Teliospores ellipsoid, cylindrical or clavate, obtuse or subacute, usually slightly constricted at septum, 35-50 x 16-23 µm; wall umber or sienna, slightly paler below, smooth, 1-1,5 µm thick at the sides, 3-6 µm above; pedicelsbasal, pale luteous, up to 80 µm long.
Hosts: Pycnia and aecia on some 30 species of Oxalis including O. corniculata (some of these by artificial inoculation only). Uredia and telia on Euchlaena mexicana, E. perennis and Zea mays.
Disease: Rust of maize causing chlorosis and death of leaves and leaf sheaths.
Geographical distribution: The aecial infection is limited in distribution to temperate regions in Europe, the United States of America, Mexico and South Africa, with one record from Nepal (C.P. News 7: 59, 1961). The uredial and telial stages are practically co-extensive with the distribution of their hosts (CMI Map 279). In the tropics it is less common than Puccinia polysora below 4, 000 feet.
Physiological specialization: Fourteen races have been distinguished in N. America (36: 466) and four in Argentina (33: 528) on maize. Temperature and light have a marked influence on rust reaction of inbred lines of maize used as differential hosts (38: 512; 39: 227) but not carbohydrates (35: 822; 39: 227). Several races have been distinguished on Oxalis (13: 572; 38: 257) and stable uredial clones have been obtained through inbreeding on Oxalis which possess a different host range. From the original culture, e.g., clonal lines pathogenic to sorghum (see Dickson, et al., Phytopathology 46: 11, 1956 and 47: 105, 1957). Recent work at Wisconsin (Phytopathology 53: 517-521, 1963) using urediospore lines P and PR, 16 aecial recombinants and 4 lines from Guatemala has revealed 6 pathogenic types, 2 new, when tested on 7 differentials; 5 inbred lines with 4 dominant alleles at the Rp locus (41: 386) and 2 inbred lines with recessive gene pairs at 2 loci both non allelic to the Rp locus. Two lines of P. sorghi formed small uredia on Tripsacum laxum, when inoculated hypodermically, the rest only necrotic flecks.
Transmission: by air (Phytopathology 47: 101-7), by seed (Reyes, Philippine J. Agric. 18: 115-128; 1953) and probably also by infected or contaminated material.
Literature: Wood & Lipscomb, Spec. Publ. Agric. Res. Serv., U.S. Dept. Agric. 9, 1956 give some information on P. sorghi and include a bibliography up to Jan. 1956. Schieber & Dickson have made comparative studies on the pathogenicity of P. sorghi, P. polysora, and Physopella zeae (Phytopathology 53: 517-521, 1963; 18 ref.).
 
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