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Mycological Society of America

Nineteen Years of Culture WorkAuthor(s): J. C. ArthurReviewed work(s):Source: Mycologia, Vol. 13, No. 1 (Jan., 1921), pp. 12-23Published by: Mycological Society of AmericaStable URL: http://www.jstor.org/stable/3753063 .

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NINETEEN YEARS OF CULTURE WORK1J. C. ARTHUR

A series of culture xperiments iththeUredinaleswas begunby the writer n I899, and continuedunderthe auspices of theIndiana AgriculturalExperimentStation without nterruptionuntil I917, making nineteenconsecutiveyears in which thismethod f researchwas consistentlyursued. The results f thework were embodied n fifteen eports, rinted n the BotanicalGazette,Journalof Mycology, nd Mycologia. It is now pro-posed verybrieflyo review hework, n orderto set forth omeof theobjectsaccomplished,nd especially o pointout themoreimportant f the changing onceptions f theproblemsformingthegroundplan on whichthe workwas projected.The cultureswere not undertakens part of a distinct hesisor circumscribedroblem. They were rather heaids in a gen-eral taxonomicstudyof American rusts,which was directedtowardsupplying technicaldescriptions complete s possiblefor everyspecies of Uredinales in NorthAmerica recorded nliterature r known to thewriter. This ambitiousundertakingwas definitelyegunsometimen thenineties t theinvitation f

theeditors fthe NorthAmericanFlora.Beginningwithmyfirst axonomicworkontherusts n I882 ithad seemed o mehighly esirableforthepurposesof a full tech-nical description f species,thateverypartof thesemicroscopicplants, apable of supplying iagnostic haracters,houldbe uni-formly onsidered, uite as muchas are the stems, eaves, in-florescence, lowers, nd fruitof higher plants,and that everymeans shouldbe takento arriveat a clear understandingf theidentitynd relationship f the various forms nd species. Noeffort hould be spared,it was believed,to make thename ap-pliedtoanyform mbrace lso thetransformationsnd variations1Contribution rom the Botanical Departmentof Purdue UniversityAgri-culturalExperimentStation. 12

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ARTHUR: NINETEEN YEARS OF CULTURE WORKwhich that formundergoes n passing through ts whole lifecycle. Many rustsare commonly ollected n onlyone or twostages of theirdevelopment, r the several stages are takenasindependent bjects,and to grow suchrusts so as to keep themunderdirectobservation nd be able to note the successionofstagesseemedhighly esirable, nd especially o fortheheteroeci-ous specieswhichpass theirgametophyticnd sporophytictagesupon whollyunlike and unrelatedhosts. It was natural, here-fore, o direct hiefattention,specially t first,owardunravel-ing the tangleof heteroeciousforms.Nobodyknewhowmanyrustswere to be foundon theNorthAmerican ontinentnd itsislands. Therewerepossibly thou-sand or morenamesin existence, uthow manyof these namesappliedto singleand independentife cycles, nd how manytopartsof cycles,or were synonyms,o one had attemptedo say.It was, in fact,onlywiththe existingnames that I had to do.It was no partofmyproblem o discovernewspecies,or to givenewnames,either npreparingmanuscript ortheNorthAmeri-can Flora, or in conducting ultures, xcept in so far as thesewere required for the systematicdevelopmentof the work.Many onger rshorter xcursionswere madeduring heprogressof thecultures, omeofthem thousandmiles or more,buttheywereall forthepurposeofmaking ield bservations ponknownspecies, and in no case for making discoveryof new species.The new speciesthatwere found were an incidental esult.The firstyear of the culturework,that of I899, was veryencouraging,nd developedno particulardifficultiesallingforsolution. So far custom was followed in the applicationofnames,and it had not been necessaryto apply any formulatodecide what constituted species. The assumption hat formson thesame or closelyrelatedhosts,havingno strikingmorpho-logical differences, ere of one species seemeda sufficienty-pothesis,nd thecorollary ecessarily ollowed hat ultureswouldshow the rangeof hosts for each species, as well as serve todemonstrate he stages and spore-formsn the life cycle. Cer-tain featuresn connectionwiththe commonEuphorbiarustdidindicatethatdifficulty ightbe found n the applicationof the

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MYCOLOGIAcorollary, nd this indicationbecame more pronouncedduringtheyearfollowing.In I902 threespecies of Euphorbiaof unlikeappearanceandgrowthhabits were found to bear non-interchangeableusts,whichwere tentativelyonsidered o presentraces of UromycesEuphorbiaeC. & P., and withthe more confidence ecause nowell-definedmorphological istinctions ould be detected. Sub-sequentstudiesstrengthenedhisview of races,and the idea ofracesfrom histimeonwas constantly eptprominentlynmind.The attempt o evade or simplifyaxonomic nd culturaldifficul-ties by treating uch races or biological strains as species, asTranzschel2 ubsequently id withthese same Euphobia formswas not favored.It was also in I902 that theHelianthus rust was grownwithindication f races,developedfurthern thefollowingyear,andbrought o a climax in I904, with theconclusion hat a numberofmoreor lesswell established acesoccur nPucciniaHelianthiSchw.,havingHelianthusannuus as a bridging pecies,follow-ingthelead of MarshallWard3in his studyof the brome rusts.No further onsiderable ffort as madetostudy aces nautoeci-ous species,or to pick out bridging osts,as it was heldthattoascertain he identity f specieswas as greata task as could beundertakenn this series of cultures, nd that studiesleadingto theseparation f a species ntovarieties, aces, forms, r othersubclasses, lthoughof muchbiologicaland oftenof greateco-nomical nterest,mustbe leftforothertimeand hands.The problemsof the Carex rusts came early into view. InI90I and I902 the threeremarkable o-species,havingtelia onvariousspeciesof Carex and aecia on speciesof Aster,Solidagoand Erigeron respectivelywere repeatedlygrown from telialmaterial, nd were called Puccinia Caricis-Asteris, . Caricis-Solidaginis,and P. Caricis-Erigerontis.As no singlecollectionof teliosporeswas foundthatwould infectmorethanone of thegeneranamed, he formsweretentativelyonsidered obe speciesand given distinctivenames, followngthe brilliantculturalmethodsof Klebahn in Germany,Plowright n England, and

2 Ann. Myc. 8: 1-35. I910.3 Ann. Myc. I: 150. 1903.

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ARTHUR: NINETEEN YEARS OF CULTURE WORKothers, lthough carefulcomparison f the threeformsmadeit seem "not improbable hat thethreerepresentmorecorrectlythebiologicalvariations f onespecies,"as was stated t thetime.In thefurthertudyof theseforms twas thought hatthetelialstagemight e foundto be restrictedo certain peciesof Carex,or to particular ectionsof thegenus,as was believedto be trueof the European Carex rusts,whichassumption n the case ofthe Americanforms,however,could not be established n anydefiniteway. The hostswere shownfinally o be even less re-stricted hansupposed, s the Aster formwas eventually arriedoverto Euthamiafor ts aecia and to Dulichiumfor ts telia.The necessity oon became acute to findcriteriaby whichtojudge ofthestanding f speciesamongtherusts, nd all themoreso because the manuscriptwas now underpreparationfor theNorthAmericanFlora. It was soon decidedthat,forthepur-poses of the Flora, morphological haractersmustbe the finaltestforspecies. Yet forpurposesof study utsideof taxonomyit mightbe serviceable and desirable to maintainthe so-calledbiologicalor physiological pecies in any rankdesired,but theyoughtnotto be recognized s speciesproper n taxonomic lassi-fication. Consequentlyn 1912 the threeCarex formswere com-bined with certainEuropean formsunder the name PucciniaextensicolaPlowr., a name which has been supplanted by P.AsterumSchw.) Kern,sincethecultural eriesclosed. Further-more,the culturesof I913 disclosedthatP. vulpinoidiswith tscoveredtelia had its aecia on Solidago, and was a part of thissame speciesheretofore nownonlywith nakedsori,making hemuchemphasized haracter fcovered elia a secondary ne to beassociatedprincipallywiththe host.Thus theidea of species amongtherustsgrew nto a farmoredefinite,lthoughmorecomplexform, han could have beenpos-siblewithout heaid of cultural tudies. A liberalviewwas nowalso required regardinghosts, and also the stress on certainmorphologicalharacters alled formodification,ut the end wasnotyet.In I9IO a number f cultureswith the Carex rust,Uromycesperigynius,evealed remarkable arallelism etween his pecies

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ARTHUR: NINETEEN YEARS OF CULTURE WORKslightdifferencen size of the urdiniospores,nd, of course, nthe teliospores differencen numberof cells and consequentsize. He pointsout, however, hatthesedifferencesre such asare to be expected in othersimilar cases. The comparisonofthesetwo formsof Distichlisrust,as to morphology,ostsanddistribution,s an interestingopic,whichneed not be pursuedfurther ere.If theCarex-Aster-Solidago-Erigerontudiessupplementedystudies with the Distichlis rust,opened up new views of thespecies question n relationto host influence nd teliosporicdi-morphism,o did theCarex-Ribesstudies disclose new views inanother direction. The firstcultures were in Io9I. As theresultsof sowingteliospores n Ribes gave peculiarly mall andpale aecia, itwas thought hatan unrecognizedpecieshad beenfound,which was called Puccinia albiperidia. Whether thisformwas distinctfrom the commonCarex-Ribes rust of thefields,distinguisheds P. Grossulariae, nd whetherAmericanformswere distinct romEuropeanforms, f whichKlebahn hadrecognizedfive,were questionswhich receivedattentionfromyeartoyearas opportunityermitted. In this tudyDr. Klebahngraciously onsented o lend assistance, nd during he two sea-sons of I904 and I906 made culturesat Hamburg,Germany,from elialmaterial uppliedbythewriter.Just s theproblem eemedsolved,and Dr. Klebahn6 nd my-self had independentlyrrived at the conclusionthat in bothEurope and America only one heteroeciousspecies occurred,whichpossesseda number f strainsor races, itwas discoveredby C. R. Orton,7while assistingwiththe rust studies,thattheoriginalmaterialof P. albiperidiaonCarexpubescens, s well asthat on a numberof Americanspecies of Carex similar to C.gracillima, ossessed urediniosporeswithonlyone basal pore, npartat least, nsteadof theusual threeor fourequatorialpores.Again the Carex-Ribes rustsof Amercia seemed to fall intotwospecies,notbased on differencesnthe aecia thistime, uton dif-ferences n theurediniospores. From I9IO onwardthe questionin this connectionwas whether r not the same species of rust

6Zeits. Pflanzenkr. 17: 132-134. I907.7 Mycologia 4: I4, 200. 1912.

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MYCOLOGIAcouldpossessurediniosporesartlywith nebasal poreandpartlywith three or fourequatorial pores. The answer involvedthevalue and applicationof pore characters n defining pecies.Afterspecial search,8which ed to both kindsof urediniosporesbeingfoundrepeatedlyn the same sorus,althoughforthe mostpart theyoccurred n separatesori, it was concludedthat onlyone species of rust was underconsideration, ut withmorpho-logical as well as physiological aces,notwell delimited.It seemedprobable,furthermore,hatthepreviously escribed,one-poredformof Carex rust,knownas UromycesuniporulusKern,was a race also belonging o the Carex-Ribesspecies,butit was notpossibleto testthematterby cultures. In this con-nection t is interestingo note,and provocative f speculation,that there is no formyet knownwith three-and four-poredurediniospores elongingunder Uromyces in the Carex-Ribesaggregation, o make the parallelismwith its Puccinia formcomplete.In 1917, the last year of the cultureseries,the principleofbasing species upon morphologicalharacters,witha greaterorless degreeof mobilityn interpretation,as furtherllustratedby the case of the Spartina rust,UromycesPolemonii (Peck)Barth.,which t was foundcould be segregatedntofourraces,9separableby small but appreciabledifferencesn morphologicalcharactersof both aeciospores and teliospores, nd by whollyunrelated ecial hosts, nd furthereinforcedysomedifferencesin habitatand geographicaldistribution.The correlatedPuc-cinia-formorthiscommon ndwidelydistributed mericanrustis thatof Puccinia Distichlidis, o-calledbecause thetypecollec-tion was incorrectlyabelledas on Distichlis nstead of on Spar-tina. Its rangeand aecial hosts, o far as knowncorrespond oonlyone of thefourUromycesraces.

At the time the culturework began the subepidermalrustsoccurringnwildgrasses nAmericawithfewexceptions, assedunder the name of Puccinia rubigo-vera, long withpartof thesimilar eaf rusts of cereals. No criteriahad been foundfordistinguishinghem,not even those which had receivedspecial8Mycologia7: 67-69. I915.Mycologia 9: 309-312. 1917.

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ARTHUR: NINETEEN YEARS OF CULTURE WORKnames, nd every ffort as consequently utforth o make head-way intothis obscuremaze of forms. The first uccess was inI902 with a formon Elymusuirginicus nd aecia on Impatiens,which became Puccinia Impatientis Schw.) Arth. The workopenedup slowly. In I903 a falsemovewas made in connectionwith the ruston Bromus,but theyear following his rust wasshown to have aecia on Clematisvirginiana.10In I907 Puccinia AgropyriE. & E., as it occurred n Colo-rado on Agropyron,was foundto go to Clematis igusticifolia,connection hat had been demonstratedyDietel withEuropeanhostsfifteen earsbefore. The followingyearPuccinia cinereaArth. on Puccinelliawas grownon Ranunculus Cymbalaria,rustfromKoeleria cristata n Mahonia,fromBromuson Thalic-trum,fromAgropyronon Aquilegia, the last threebeing de-scribedas new species. In 1915 aecia on Hydrophyllum romUtah weremadeto growon Agropyronnd Elymus,givingriseto uredinia and telia similarto those fromthe Ranunculaceousaecia, but believed to constitute distinctspecies. In I916anotherrust on Koeleria cristatawas grownon Laciniaria underthenameP. Liatridis (Ell. & And.) Bethel. Repeatedattemptswere made to findthe aecial host of the common eaf rust ofwheat,P. triticina rikss.,but without uccess,althoughthereweremany ndicationshatpointed oa Ranunculaceoushost, ndespecially o ClematisorAnemone. It was thoughthata favor-able trialon Clematis lammula wouldgivea measureof success.At any rate it was believedto be one of thenumerousraces ofthesubepidermaleaf-rust f grasses,P. Agropyri,withRanun-culaceous hosts for its aecia.11The serieswere discontinued eforethe studyof the subepi-dermalformswas completed,uttenof themhad beenconnectedwith theiraecia. The convictionhad been growingfor sometimethat some of theseten namesrepresented aces of PucciniaAgropyri, ather hanindependentpecies,as was stated n dis-cussingthe cultures of I912. When the manuscriptwas pre-

10For a full account and explanationof the mistakeof I903 in supposedlyconnecting ecia on Dirca with the Bromus rust see Journalof Mycology I:62-63. I905.11Mycologia 9: 276. I917.

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MYCOLOGIApared for the North AmericanFlora P. tomipara, . Agropyri,P. cinerea,P. alternans nd P. obliterata,s well as P. triticina,wereplacedundertheonenameofP. Clematidis DC.) Lagerh.It is considered greatadvance to bringfromthe limbo of P.rubigovera, ix distinguishable pecies,some of themhavingaconsiderablenumbero.frecognized aces,and therebymaking tpossibleto relegate o obscurityomedozenor more names thathad previously eenencumberinghe iteraturef therusts.In a somewhat imilarway the AmericanCarex rusts were inutter onfusion t thebeginningf thecultures. Theywerequitegenerally alled Puccinia Caricisor P. caricina,no cultureswithAmerican materialhavingbeen made,and diagnostic haractersnothavingbeen well workedout. Altogether en speciesweregrownduring he culture eriodto showtheirfull ifecycle, nd.in severalof thema numberof races was found, ncluding heone-celledUromyces erigynius. Of course,beingable to sepa-ratethesetenspeciesmade itpossibleto decideuponthe dentityof other pecies,whichwerenotactuallygrown.A view generallyheld whenthecultureworkbeganwas thatthehostsof an autoecious pecies,or of each of the twopartsofa heteroecious pecies, would be found to be closely related,often, ndeed,to be but a singlespecies,or genus,and certainlyalways withina single family. Consequently t was felt thatwhen grassor sedgerustwas successfullyultured,heproblemabout hosts forthatspecieswas practically olved. This com-placentopinionwas quite upset n the case of Puccinia subnitensDiet. on Distichlisspicata,which n I902 was first rownuponChenopodium lbum,. In I904 Rev. J. M. Bates of Nebraska,who had made the field observations nd suggestionsfor thiscombination, rotethathe had been continuing is observationsof thisspeciesand believed hat thad aecia also on hostsbelong-ingto twootherfamilies,which seemedto thewriter t the timeas most ncredible. Tests,however, howed twould flourish nspeciesof Cleome,Lepidium,Sophia and Erysimum, s well ason Chenopodium, ompelling he admissionthatit would grow"with equal vigor upon species belonging o three familiesofplants," t thetimebeinga " remarkable actnotknown forany

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ARTHUR: NINETEEN YEARS OF CULTURE WORKotherspecies of rust." Additionalgenera in the same familieswere added from imeto time foraecial hosts,until n the cul-turesof I916 thespecieswas grownon Abronia and Polygonum,thusaddingtwomorefamilies. Mr. E. Bethel,of Denver,Colo-rado, who made the fieldobservations nd suggestionsfor thelater additions,has continued the list since the cultureseriesstoppedand brought he numberup to 76 species,belonging oI9 families,12 truly stonishing howing, nd all themoreso asno clearlydefinedraces have so far been detected. The onlyotherspeciesof rust withsuch a remarkablyxtended eriesofaecial hostsat all approachingP. subnitensDiet., is that of P.Isiacae (Thiim.) Wint. from the dry trans-CaspianregionofwesternAsia, as reportedby Tranzschel.13 This species withtelia on Phragmites ommunishas aecia on I9 species of hostsbelonging o 9 families, he aecial familiesbeingthesame as forP. subnitens.

In still anotherway the conceptionof species was modifiedwhen n 1905teliosporesfromRuellia ciliosa weregrownon thesame hostand also on R. strepens. The latterhost,with oose,watery issues, ave risetoaecia fully enpercent. arger neveryway than did the formerhostwith ts firm,woodytissues,thusshowing hatthe forms ecognized ytheSydowsunderPzccinialateripesB. & Rav. and P. Ruelliae (B. & Br.) Lagerh.14 epre-sent only a host influence-uponne and the same species,thisinfluence eingtraced notonly n theaecia, but also in theotherspore-forms.Thus itwill be seen thatwhilethemainworkof thecultureswas effectiven completinghe life cyclesformanyspecies, ndin some cases extending nd definingherangeof hosts, t wasat thesame timemostprofoundlymodifyinghecurrent oncep-tion of species amongthe rusts. Instead of a rigidideal of afew invariablecharacters nd a limitedrangeof nearlyrelatedhosts to be determined y cultures,we have substituted com-plex of somewhatvariablemorphologicalharacters s thebasis,

12 Bethel, Phytopathology: 193. I919.13 Beitrage zur Biologie der Uredineen. Trav. Mus. Bot. Acad. Sci. St.Petersb. 3: 40. I906; 7: 14. I909.14Sydow, MonographiaUredinearum : 235. I902.

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MYCOLOGIAwitha more or less extendedrangeof hosts n partdeterminedbycultures nd inpartby microscopicalimilaritiesnthefungus.A speciesat thebeginningf theworkwas conceived s a simpleand direct succession of individuals of the same appearance,capable of beingdemonstratedy cultures, ut at the close hadbecome a bundle of somewhatmobilecharacters, ftencompris-ingmanystrainsvarying hysiologicallynd sometimesmorpho-logically, nd to a more or less extentnot interchangeable ycultures.

In some other ways than already mentionedthe acceptednotionsregarding ustsweremodified. It was foundthattelio-spores among the grass formswere not all necessarilyrestingspores, ndthat henon-restingorms resented pecialproblems,whose solutionwas not faradvancedwhenthework came to aclose. Assistancewithfieldobservations nd materialpermittedsuccessful ultures obe madeinMay, I9II, withtheaeciosporesfromArabis sown on Trisetum. The Arabis aecia arise fromsystemicmycelium xtending hroughouthe stemand leaves oftheplant. A month aterteliospores esulting rom hisculture,nowhavingbecomemature,werefound o be capableofgermina-tionand were sown on seedlingrosettes f Arabis. The resultsof thissowingfirst efinitelyhowedwhen theaxis oftheArabisbegan to elongate as growthstartedthe following pring. Aculturewas similarly arriedout in I903 withPucciniaEatoniae,usingtheaecia on Ranunculusabortivus, lso a formwithdif-fusedmycelium, ut a reciprocal ulturewas notmade. Thesetwo species of rusts,havinga systemic ormof aecia, were theonlyones of the kindwhich werebrought nder culture. Theybelongto an interestinglass physiologically,ith ystemicecia,andwith eliospores apableof germination ponmaturity, hichpossiblydo not retaintheirviability hrough hewinter, r onlyto an impaireddegree.The cultureworkbegan with the too prevalent dea that allrustscouldbe expected o conformngeneralto the wellknownPuccinia graminis. It closedwiththe conviction hat the rustsare fartoo diversifiedn theirmorphology,heirnumerous har-acters,theirphysiological daptations, nd theirrangeof hosts,

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ARTHUR: NINETEEN YEARS OF CULTURE WORK 23to be represented yPuccinia graminis n more than one out ofnumerous spects. In thisresumeof cultures nlya fewof themoreprominent evelopmentshat shouldhelptomodify hetoorigidand restricteddeas of rustspeciesas commonly eldhavebeen broughtforward. Yet enoughhas been said possiblytoindicatethevalue of whathas been accomplished nd the needof more extendedworkalong similar ines.

PURDUE UNIVERSITY,LAFAYETTE, INDIANA.

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