Schafer, J. F.

Zimmer, D. E.

English

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Variability of Teliai Formation of Puccinia coronataDavid E. Zimmer and John F. Schafer, Purdue UniversityThe variability exhibited by the crown rust fungus, Puccinia coronataCda. var. avenae Fras. and Led. is not limited to pathogenicity differencesbut also occurs in other physiological characters. Differential developmentof the teliai stage has been observed for a number of rust fungi. Previousinvestigators attempted to show by experimentation or observation thatteliai formation was affected by differences or changes in one or a combi-nation of the following: (1) condition of host vigor, (2) stage of hostdevelopment, (3) relative host resistance, (4) inherent character of thefungus, and (5) environment.Waters (12), Johnson (4), and Gordon (3) have reviewed and dis-cussed the literature on factors affecting teliai formation of rust fungi.Magnus (5) in 1891 first proposed that the relative condition of the hostplant affected the occurrence of telia. Gassner (2) concluded that thedetermining factor was physiologic aging, the stage of host developmentgoverning teliospore formation. Bailey (1) subsequently reported thestage of host development not to be important for P. graminis Pers. f . sp.avenae. Parker (7) reported that the production of telia of crown rust onoat seedlings was related to host resistance. Murphy (6) observed asimilar relationship on both seedlings and adult plants. Parson (8),however, found some cultures to form telia as early on susceptible varietiesas on resistant.Raines (10) believed that the protoplasmic constitution of the fungusitself was the important factor, finding wide differences in the tendencytowards teliai production in different cultures of the crown rust fungus.In further observations of such differences Bailey (1) and Gordon (3)reported a correlation between virulence and rapidity of teliospore develop-ment for cultures of P. graminis f. sp. avenae. Parson (8) and Murphy(6), in contrast, suggested that early teliai formation may be character-istic of narrowly specialized races of P. coronata. Parson as well asMurphy also reported that some cultures of P. coronata studied neverproduced telia. Murphy observed differences in teliai development amongdifferent cultures of the same race of P. coronata.Waters (12) reported teliai production to be related to a lack ofmaintenance of vegetative vigor and thus influenced by any internal orexternal combination of factors affecting this, such as light, temperature,or moisture. Peturson (9) and Simons (11) showed that telia of P. coro-nata developed more rapidly at 25° C than at lower temperatures. Johnson(4) and Gordon (3) found that higher temperature also favored earlyteliai formation of P. graminis f. sp. tritici and P. graminis f. sp. avenae,respectively.The present investigation was undertaken to obtain knowledge ofteliai formation pertinent to the development of telia for studies involvingthe completion of the life cycle of P. coronata. A preliminary report hasbeen made (13).9192 Indiana Academy of ScienceMaterials and MethodsSingle monosporus cultures each of races 202, 203, 264, 294, and 295and 3 monosporus cultures of race 293 of P. coronata var. avenae werestudied. The relative rapidity of telial formation on seedling and matureplants of resistant and susceptible host varieties was investigated byinoculating each culture on the oat varieties, Appier (CI 1815), Bond(CI 2788), Canuck (CI 4024), and Clintland (CI 6701). After incubationthe plants were placed on greenhouse benches and observed daily for theappearance of telia. Appier and Bond were susceptible to all culturestested ; Clintland was highly resistant to races 202 and 203 but susceptibleto the others; whereas Canuck was susceptible to races 202, 203, and 264,but only moderately susceptible to the cultures of races 293, 294, and 295.The influence of temperature on telial formation of races 202, 203,293 (culture B), 294, and 295 on these oat varieties was determined byinoculating seedlings and subjecting them to constant temperatures of60°, 70°, and 80° F at a photoperiod of 16 hours.Races 264 and 293 (culture C) which did not produce telia wereinoculated on these 4 and additional oat varieties in the seedling, juvenile,and mature plant stages. These inoculated plants were subjected to oneor a combination of the following treatments: (1) temperature fluctuation,12 hours in light at 80° F followed by 12 hours in darkness at 60° F, (2)low fertility, (3) low soil moisture, and (4) removal of infected leavesand floating upon a 7% sucrose solution.ResultsThe results of the test with different rust cultures, oat varieties, andstages of growth are presented in table 1. These show that differentTable 1. Days after inoculation of seedlings and mature plants of4 oat varieties that telia of P. coronata were first observed.Race Days to telial formationVariety : Clintland Appier Canuck BondStage : Seedling Mature Seedling Mature Seedling Mature Seedling Mature202 14R 15R 17 16 20 20 18 18203 24R 26R 20 22 22 25 29 19264 *293A 14 21 14 23 24 26 16 22293B 18 23 17 22 22 25 18 20293C *294 21 24 23 21 20 24 19 19295 16 18 17 19 21 29 16 21R = Res;istant reaction* = No telia produced Icultures of the same race as well as different races vary in their abilityand rapidity in producing telia. No relationship was shown between thevirulence of a particular culture on the differential variety Clintland andthe rapidity of telial formation, nor was there any relation of host resist-Botany 93ance and susceptibility to the rate of telial formation of the 2 differentialraces, 202 and 203.The time required for the initiation of telia following inoculation ofthese 4 varieties in the seedling stage with the 6 telia-producing cultureswas generally less than the time required on the same varieties inoculatedin the mature plant stage; however, the relative differences varied widelyand exceptions were found (table 1).Increase in incubation temperature decreased the time required forthe initiation of telia (table 2). The difference between 60° and 70° FTable 2. Days after inoculation that telia of P. coronata were firstobserved on 4 oat varieties kept at 3 constant temperatures.Race Variety Days to telial formationTemperature: 60°F 70°F 80°F202 Clintland 25 18 14Appier 26 20 17Canuck 28 24 19Bond 28 22 17203 Clintland 32 24 22Appier 31 22 20Canuck 33 24 21Bond 30 21 16293B Clintland 28 23 16Appier 28 21 19Canuck 29 25 28Bond 29 22 18294 Clintland 29 24 16Appier 31 23 19Canuck 30 24 20Bond 28 21 17295 Clintland 23 19 16Appier 26 23 19Canuck 27 24 20Bond 24 21 17AVERAGE 28.3 22.3 18.3resulted in an average decrease of 6 days in time of telial development of5 cultures of P. coronata on 4 oat varieties. The difference between 70°and 80° F further decreased the time required for telial formation by4 days.The culture of race 264 tested and culture C of race 293 did not pro-duce telia under any experimental conditions including the addition ofother host varieties to broaden the available range of host-parasite inter-94 Indiana Academy of Scienceactions, fluctuation of temperature, subjection to low fertility and lowmoisture, and floating of detached leaves on a 7% sucrose solution.DiscussionRapidity of telial formation does not appear to be characteristic of arace as defined by its specific pathogenicity, in agreement with the earlierreport of Murphy (6) . Although 3 cultures of race 293 tested were similarin specific pathogenicity, they differed in their ability and rate of telialformation. Two cultures produced telia readily on all varieties tested,but at somewhat different rates, while the remaining culture was similarto race 264 in that it did not produce telia. Race 264 has different specificvirulences than race 293 and a wider range of virulence. The similarityof races 264 and 293C in failing to produce telia and the differences amongthe cultures of race 293 suggest that no correlation either positive ornegative exists between specific virulence or range of virulence and rateof telial production.All telia-producing monosporus cultures developed telia more readilyon some varieties than on others. Thus, telial production is not dueentirely to inherent tendencies of the rust. None of the 4 oat varietiestested affected in a consistent manner the rapidity at which a number ofcultures produced telia. Therefore, the rapidity at which an element ofthe rust population produces telia appears independent of reaction typeand host variety as well as specific virulence or range of virulence butdependent on the specific capabilities of the rust entity concerned inrelation to the specific host-parasite combination.The results obtained with the effect of temperature on rate of telialdevelopment support the previous work in this area.Failure to stimulate races 264 and 293C to produce telia suggests thatthese cultures may lack factors essential for telial formation. As themajor source of primary inoculum of the cereal rusts consists of airborneurediospores, it is doubtful if this deficiency has any adverse effect onperpetuation in nature of such a rust. The inability of a particular raceto produce telia may actually favor multiplication in that uredial produc-tion continues throughout the growing season. Gordon (3) proposed thatthe rapidity at which a given race of P. graminis f. sp. avenae producedtelia was inversely related to the prevalence of that race.SummaryEight monosporus cultures representing 6 races of P. coronata var.avenae were investigated for telial formation. The rapidity at which aculture produced telia was not correlated with range of virulence of thepathogen, specific virulence of the pathogen, resistance of the host, orhost maturity. Rapidity of telial formation appeared to be a function ofa specific relationship existing between the particular host and parasite.Temperature was found to directly alter the rate of telial formation.A culture each of races 264 and 293 did not produce telia under any experi-mental conditions tried, and thus may not have the capacity to producetelia.Literature Cited1. Bailey, D. L. 1925. Physiologic specialization in Puccinia graminis avenae Erikss.and Henn. Minn. Agr. Exp. Sta. Tech. Bui. 35, 35 pp.Botany 952. Gassnek, G. 1915. Die Teleutosporenbildung der Getreiderostpilze und ihre Bedin-gungen. Ztschr. Bot. 7 :65-120.3. Gordon, W. L. 1933. A study of the relation of environment to the development ofthe uredinial and telial stages of the physiologic forms ot Puccinia graminU avenaeErikss. and Henn. Sci. Agr. 14 :184-237.4. Johnson, T. 1931. A study of the effects of environmental factors on the variabilityof physiologic forms of Puccinia graminis tritici Erikss. and llenn. Can. Dept. Agr.Bui. 140, 76 pp.5. Magnus, P. 1891. Ueber das Auftreten der Stylosporen bei den Uredineen. Ber.deutsch. Bot. Ges. 9 :85-92.6. Murphy, H. C. 1935. Physiologic specialization in Puccinia coronata avenae. U. S.Dept. Agr. Tech. Bui. 433, 48 pp.7. Parker, J. H. 1918. Greenhouse experiments on the rust resistance of oat varieties.U. S. Dept. Agr. Bui. 629, 16 pp.8. Parson, H. E. 1927. Physiologic specialization in Puccinia coronata avenae. Phy-topathology 17 :783-790.0. Peturson, B. 1930. Effect of temperature on host reactions to physiologic formsof Puccinia coronata avenae. Sci. Agr. 11 :104-111.10. Raines, M. A. 1922. Vegetative vigor of the host as a factor influencing suscepti-bility and resistance to certain rust diseases of higher plants. II. Amer. J. Bot.9 :215-238.11. Simons, M. D. 1954. The relationship of temperature and stage of growth to thecrown rust reaction of certain varieties of oats. Phytopathology 44 :221-223.12. Waters, W. C. 1928. The control of teliospore and urediniospore formation byexperimental methods. Phytopathology 18 :157-213.13. Zimmer, D. E., Schafer, J. P., and Gries, G. A. 1960. Studies on teliospore for-mation and germination in Puccinia coronata. (Abs.) Proc. Ind. Acad. Sci. 69:107-108

Variability of Telial Formation of Puccinia coronata

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Variability of Telial Formation of Puccinia coronata

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