Tobacco Documents Online

2060457998

. The Genus Nicotiana: A Source of Resistance to Diseases of Cultivated Tobacco L. h. I3I-BIC aso H. E. IIEGCEST.\D1 Nicotiana nhacum L., cultivated tobacca, ia ona of 65 specfa in 1hr jrnur Nfeeuana. Orer ehr Pasr 30 Ye.rs, reryi.l , mben of the apecia boe been ndnded in teau of resisaance te tabacee dise.ns bl r errb s,ohers in <o- bar o-prodarinl areer throulhoue the rurld. This reporr tumr,s.r(res these oritations i tabnfn Jorm end discussrs meahods rberrbr inaerspeciFr n ns/er of dheare rnisrance mq be accomplishrd. 3mong the many und varied species in the genus \-irnrimtn is Sirntiuun In6ncmn L.• common tobacco, the most variable of all. In its many polcmorphic, botanical, and rultivaled fonns it represents an impressive array af gerns plasu. -Sin'ularly enough. reports of the occurrence of S. taLnrenn in the wild state have not been recognized by Goodspeed (1954). Cytological evidenee sug- gests that it is an unphidiploid which oriei- nnted irom a chance cross between an an- cestral form of present day S. splrestris and a primitive member of the TomrNosar( prnhably it i: a distant relative of \-. otm pLnrn. vnd both speciee are cunfluent in s region mhieb includes northwestern Arpen- trnn :md adiarent Bdivia. If tnbnrvn esistod as a wild species, it did so for a relativel}' short time before hecmning domesticated, and itt polymorphism mac be niore a fune. tion of nurture than nature. Serertheless, this vnrinbilitv represents a tcenlth of genn plasm which has heen exploited for diseax resistance and other quality rlmracteristics. In addition to this broad base of gernt plasm, there are 04 other species in the genus with exploitable characteristics. During the past 30 years, varying num- hers of Sirotiann species have been included in studies of disease resistance. This review attempts to summarize the results of these investigations, and it ciearly indicates the diversity in disease reaction amone the Vic- niinnn species and their potential for ex- ploitation by plant breedezs through inter- . r Genetielrt and Principal Pathologut, re- speetivelp, Crops Research Divieien, United 9t tes Department of Agriculture, Beltsrille, \far'land. Rceeived for publicstion March 9, 1965• specific brhridization. Tbr preseuei, in to- haeco rarirties and breeding litwa. ut muun- genir donsinant resistance to tohaceo mosait virus jT1R-1. •rildfire (R-F), and hluck root rot (RR) derived itvm thrre diHcr- ent Sirotinorr sperir prnvidrs the pn•erdrnt (Fig. 1F). Tobacen disease-resistautr breeding in the United 9tutes begsn with Jnmts-.lnlw.mi nhout 1912. Prior to that time, the imprm-e- ment of tobacco ns a crop plant depcutied - more on selection than on inten'arietal h" , bridir'stion. Johnson (1914) dm'elnped vn- ricties Imvinp rosistance to the hlaek rnnt nrganisnr [ThirlnriopsTs bnaicnln (Bork. and Br.) Ferr.], With increased and i.intiuuod rultivntimn• aimilnr controls were needed for other disenses. Each of thr diHcrent tu- bneco types such as cigar-filler and cigar- n-rapper. Aue-cured. bttrleT, ]Otryiaud. nud dark tobnccos require the development ot' a different set of resistant varieties. Ahout 1922, rresistance to the black dmnA fungus [PhtrrnpLtLorn pnrnsiflrn IDast.) var, n(eorianac (Bredn de Haan) Tuclrcr] u'as found in the varieties Big Cuba aud Little Cuha by Tisdale in Florida. By e process of hphridization and selection (Tis- dale, 1931), cigar-wrapper hreeding linea with high levels of black shank resirtsnrc were developed. One of the hetter liues. Florida 301, has provided mest of the hlacA shank resistance found in current varieties of all tvpes. More recentlp, black shank re- sistant getm plasm from other Sicntinna species has been used in varietal develop- ment. The aomnplexitg of the task is em- ` phasized in the work of Cnlleau et al. (1960), Apple (196?), and Chaplin (1962). During the 1934-36 period, n search was mnde for resistance in S. tabanrm. Over rc 2060457ggg

SHL GL]oS YLCOitAN• ;, ;nun seed ruilretions trerr, ohtaiued prinur- iic front are:w of ahoriginal culture in Cen- red +ud South ~wericn and the lCest Indiea. C iopton nnd as-ocintes in Tohneeo Itn•estiln- [inns. Crops Research Division, USDA, ecs- :rmntiealiv creened this collection for re- .istnnce tn discu•e. Their inrestiOatiuns .'irjded a source of resistnnce to Granville +vilt e:tnsed he p+:•udnnr..nra,e .eLnurrrnrvnr~ •F.. F. $utilb) in T.I. 435A. nn iutruduetiun rmn CnlnmLin IClnvtnn nnd .¢wirh. 19.j'1). ::u[j re>i=Wntt' to root-ktmt neumtode Jfrl- ., mmnrr -p.i in T.I. 7uG. an introduetion :ram fIourinrns tClavtmr.1B$). Re.istanrr " tnhar", mnsair viru- i]/arrnnr mbnrf Iiolnw.l n-as fmmd In' Solla :rnd limryv i9i^i m tbr rnrirtv .1u:imirur.r Gnm 6_ i~mirin. S-ntnrtunstrlc. drr mnnr breedinz line= imrm= re-i.rmrr n. un.an' 17nni tht- -nutrr iarkrd pond aptalitv. Thrr-. this wa- -,:.rl ili-ranirrl h". hl:nu hn•erier. it -uvnr o' rrvt.tanac rnutrnilyd iro n _•wr Iilnnmaur Inrtt.r lirrirr1I tnS. nfb•- Tin• vman tn miuidr S_ od.r.r.u.. irad -rred iu prnridinc rr.istanrr tn diara-r mn~ inv.vutrd hc V:dlrau rl9,i'_+1. jrt 191i;. Clsprnn tn'r-•e8 thr imp~'rb+nrr of iirritabhhInn. aI' rr-i-t:nrrr nI rnmhiunti"u .ritli ntiier nivthnri- ni di•raa• rnnn'nl. Clartmr :'953 1 ....ral.:rttrutirur u' thr Ylr..- r,rnr.. amrir. a, nririitimtnl -nurrt. ol rii-- ra-«-rr.iztnnt crrw tiin-w. .\n asrellrut rr- rie+r paprr mt the apl+iirntmn and limita- unn+ ni intrr+Pooitit hrerdutc iu \-lr~~rumn n'as prr=rutrd r'rentlc ny llnnn et al. ~19f°I. Tite rira: vxnressed hr Clapton. 4alIr:ut. ami U:um ualr hreu amply ~up- pnrted hv- thr •protarular rt'sults in tnbar- ' rii"•n-r rrsi'ttner Ivrcdiug mitirit harr .rn nbtnmed by extending du• ran7r nt hre.•din_ invt•stigntinns ftaw thr intruepr- '~nir to the interspecific lecel. Sonrithstand- iuc tbe errrllent rwnjn: nhtained. it shnuld he pointed ont thnt ttie dinance in tinte be- tn'een tlte )+rnductiott of tlm nripinnl inter- •pecifie F, hybrids and the breeding jines nnd lm'ieties deriaed frmn them mar •pan tnna thsn ^_0 prars and 40 -ent'rntians. Ilr- rAnprrrcnt of n diseasr-rrsist+n[ tnbnrrn rn- rirt!' includes salutions to a nuzr nf cctn- ;rnrtir problenr+ hz tlir rnmbinrd t•flm2c nf unnr +rnrken nt Frder:tj. ct:rtr. nnd priratr ."trlr rentrfs, incimiiu_ rinnlitp erolnn• Lions by tobacco manufacturing cotnpnnies. Intehpecifie In'bridixxtinn iu .\'ir.rllmrn u•as known before Hendelianism, but its prneticai itnplitatiaut for tohncen improre- went began with tlte ++'ork of Holmes. Hoinres (1935) made a ntuu6er nf rrosses vrith varieties of S, rn6ncunt and the syn- thetic, fertile nilopnlcploid, species-h.•hrid ••IL~luta:' 4X (clutiunsa-taeahtunI, docel- nlmd bp Clnn•en and Gondy+rrd 1t9'251. A mrirs nf backcrosses ro thr nt'ietr Smn.mun re•tnred tile e.-ential pltenotepc of Samsnun and pmrluced a =[t'ain (Hohims' Sanssnun) trhiob hred true for resistmrc v, rm.monn (nbncva uto,ule eirn-. Grr-teI 1151411 iin+erd thnt in Hojnui Snmsotur an alien ehrnv.u- ,ntur ;nh+tirntiml Imd rakrn I'Inrv; thr paie of N. 0111111111 chroino.mne- Lad hren rrPinred br au :malocnn= "H" I'au' trnm C, niotiun•n, jndepondent .tutiie< Irc (llca ;79G71 prmhtrrd n •imil:u' alioiL •uh-titn- pun r:mr. I~xih_ thr \-. rrlnnne.u .nurrr. i-elir:nt ~19.in_1 Jrarlaprd tb'Bnt un•.m.- rr:i=[nut burjrp curit'tic-. .\pparrnti}'. rr- pratrd harkrm..in2 aud rt_id -irrtinn -orved in i•nlnm pl:nn= it trhirh du-rentrnt .~f riu-oum.mnr G+n.. Y. .dmlr.•.-... r.n +cliirii tLe t'r-i•nuu f:trlnr n'n- rart•ird. bad <nme- h.mhrrnmr n'auanealr~l b. thr •'jj" ..ivnnw- -nrnr nf T. (r•lr,.r-nn. . Iu rmfrnt hrndiu°, liuv- nuri r:u'ieur-- nm-air n•-i-nuum hr. imvr. a, n wmtosrniv dmniuant: ami )Irn- .irli:ni ratiaa e:w Iur~prrb•d in prownir< t}nni hen•rnzyrou: piauls. Ill all pl'nhaLil- itr. Lmct•err. thc rrnu.lnrntrd sr_-meut i- •nf. Arirntir lar.r that tbr derirnd rhrenun=nwr slintv: t•mnidrruhle adinitr C+nIhr -'H^" eiu'nntosome in Hnintri Santannn i(;rrZel awi }3w'k. 1gGn). In the initial nttewpt tn trnn-fer re-kt- aurr tn the tcildfira nrcnnism [P-r~rrt.uu•nnr. rnLnri (Wolf nud Fn~teR F: L. ~Irren=i f) ntn S. lr.nnipnrn Car.. Clnrtnn 119i9) experienced rotuiderable dil&njtr ill pm- dncintt the intcrspeeific hybrid. rnLnernu_ ImrnlOnrn. The rross heheeon thr diplnid fanns of SX lnbarnnr nnd S. 7nnyrBnrn pro- dured secdlin_= ahiAt nsnnilc failed to zrmr beevrond the cotpledanare stnge. A crns. hncwern nutntrtrnplnid fnnns nf thr.r spr. ries. Lomercr• resulted in a plant with suRL ritmP fortilih' to pmrutit fnrtlter barkrrnss. ing and selection. in screening adennced :rnrrntion• nf evildfirr-rrerstant hrrrdinp 2060458000

48 ECC\UU1C BCilxi Fig. 1. \-F Pictorial outline of the interspecifie transfer of black root-roe resismnre. A. ,\'iru• tiaan deberyC black rooPrut-rrsistant species. B. Fertile intrnpeciRc Ip9rrid. 1S(drL,iey,- :nbaeum). C. Segregates fron. tLe BC,S, generntim,. D. 8oota of n resistant and saceptiblc plavt from a segregnfing Populotion. E. Bnrley _1, a tahaero variety ,rith roautnnee to to- boeco mosaie rirus derired from Y. nlntmnsa and resixtmme to n'ildfire derived from Y. toani- ;tera. F. A b.eeding line nith raivtnuco to tobacco mosnic virus and n'ild8re like Bnrley 21 but rcith additional rcaistanee to black root rut dericed from S. dtbnryi. . fines, it was possible to mass-inaculate seed- liugs in plant beds, nhich served to increase population sise and permitted critical selec- tion of reeistaut varietal types. Folloaing six backcrossea to buriey varieties nnd by continvous screening for vgronomir type and disease resistance, the firat variety, Bur- lep 21, with cotuhined mosaie and wildfire resis[ance, vas developed br He eeslnd et al. (1960) (Fig.1S). Resistince to blaek mot rot was found in the Austnlian species •\-, drburgl Dmuin, (Fig. ld) and transferred via intenpecific hybridization to fertile hrecdin; liues nf S, tobnnrni by Clayton (Fig. 11. The pmce- dure u'u essentinllv the same n% that de- seribed for the transfer of wildfire resist- ance. Hybridizations hehrecn breeding lines re- sistant to mosnic nnd wildfite, and lines re- sistant to root rot luve produced hreeding linea with romhined resistance to thrse dis- ra.cen IFi„^ttre IF). Sueh inultiple dis- ease-resistent lines are nov in an adranred 206045()001

THY. t[C]ty ]IQYr1.1YA 7[I =ts_e of decelopumnt. Gcnneic cridunrc olr- L; ettrrwe esnwple- nt' rru.. etrrilitr. it tawrd frm;; •[udie. r•1' :wdtiplr <ii-r~:nr-ra nmr be neeessnry to mnke o bridge eross 6y rictwtt litm- imiicates that the tLrer fa<tors uriug nu inrrrwadiate ur L~id!liqn cPrTttro :.rr born;• it -rparotr rhrorun+mur.. .yrp:u+ I IIurlc and Dropltin 19G11. The n.ual prn- rntly. the trnn•Inrate:l crrtuents Itavr hrrn redm~e nt interqmcifir I6yhridir.ntiott i• fnl- rrdnoe<I in wxr tn thr vz[ent thnl thry uo Imred. exeept tlut rttt interntedinre speciea is Inn_er interfere witL um~iunl ]Icndelimt rn- u,ed e_ e rrrnrrnnl par;•ut v'tt6 Ibr uu<. rrzic[nnt <Ireeie<. Iu Inu•r haelcem<a 'muera- unu•t frci-tmlt ylamt, eur rra-*nl "tth N. Interspecific Hy6[idiz3tion r•d•rtru;r n• emnpletr tLe hrid;r. Thr zeulm~ 'Chr iuinai ucLri:iizan;ru I;rr Ilu• iulrr.rv- :nttL•m rrrrutk medr zu•.h e hritl_^. rr•.-_. ~iLr~ n'anyrt• ~~f _.a•w ui:nn; eau Lr mndr iu i.r.. f,tJSirrlmwint t.clcr.n~nr .-cio~- .. ;nt;:;i;r.r ~~1 v:rc, 'rh•. yuqrir.l ;:n•luwi, u".I ._cl•~:.,u~i. ::wi I;•rry tlml mum;_ ei_LI rr_i=taul Pi . pLmn /' dnl tnil prndnrr _1 m6rn I~•JLn:;u.ri .Fr he- . \- , rd....... .... fp; Il;r 6:r:i- n( ~rn.lneienl In ..ILrr v~rkrr.-t. tn l;rndn•~r u;r L p:;r.-n: in . •nuln+ ~i1 li;r h:i;l_rd _r~;;rrnturn ~n :- n~i,..r~._, ri:rn;nn=nmr ...... ph^n•nt rnu- liu. u•• • sp- wn~v -n.rdnv i;;n.n rr- tLr <trr.. :rlrlv 19 X :r;rri u::;t r~ill •.n- . rru::i rr.. _rw.rati.•; .;crt ~ umu-In nnrirn, ur.~ifoI;.~In'Id l T- :nui zrill h, Lrr;;:. i y ;~.o. ~..b.e tl tm;•r_ u.• a n .. . arin.vLi~. 1~. 1' n.•at;.;i tcrn~ rnlri;i..:ur [.~ rrclnrr :rv'nim. Irrtli;~:dl..n..ivpi.miP;'lin.-.•-~;n;. 16~-arrl; aI irl•rr-:o..u-n•uu•ri t.. uu. rLpLmi ;~m.ratn~u rr.nn; :6, -\n;pivirii- Iv t;a~liir Lnr•~_pr:~itn. }Irwinii:m .p-n~m. r~.~.•.•.•.•.. pnmuL ••^•a-un;nllc iiwl r:ro ~.I.....ilu. Lrrr•ilue -••;w.- LCLoe u;rra- ulsn.(. nor•auidb c :. n.unr.;iurd tuu.... u io:n uI :rdz:mt:r.... .u- t., ...... nm~ILrt. ~,tum;d•.. -.•r;;.. ...;r riw,- tit.. Iiin..tl. 7iu- iz s.. I..rw -.i-. vnb..- y...... l •-..e- u.u::llvirv tl:.. rr..., ns.vm;••un ur. . rtL div :;;in•.r.•:i c_I•;.r;v_:: ;otinvi lavnrni I;c 1•,: ;;•rrs- nd;rr ran..r•- ;uav pr,.inrr :;n (ir:tlm; .urri ll:om , lqltlr m ........... . nh;uuiaur:. ~n .rr•ri- u~hnl; crr;.nuat, trl: nt sure u nr~.rrrinrr t- ~~ireiou., :;ud v.ltilr hnt 1ai1 tn :rnn' hrormi tl;r r..nionnrc tl;r arrcvu:;: Lvnrrd :•~t I;r iu;i;nairn•d it. rrn__r_ nl Ilri- rvpr r .~ ;eir tlnnu_I: =rrd :urrra.;!~irl nrnr Iv- urv.-;•rvrd -••'dlin_ .rLvL =m'cicr_ o. mmrumit. rntw[i- In~ mn ul =•ml:cr Lrr;pvcatir~u. Thr Inu~ ;.lu+~r... i'ndrr.url; n i• \'. :...•~•••~~. f..r dtr inrsl'n';rnre:i vorsrr t•~ a - ~ • . . m r~piovl. mr thr w:urruai mi:! n; :nrv iu- •'rnt ILr .iu21r -nrctrnr a, n eali;i hrimtd hchriI is rm;-idrtmd adviz;thlr hr. zrhen it :nur turfrlc Irr •t rontnnlinan[. an •au.. nf tl;r drerlrqnnrnt ;d' ~rtnlrla.nm. :n;dr;r_ aJr prnrlnrr iu tl;:• rvtnpln=:;. .,i tl;r ma9•-ctrrilr flm•al mudilicntirnn mhirh nrrue vrtwtrrual zprrie.. m• a=enn.ruie Imninid m' iu rrr[ain iutrrcprrifir rrn_.<.. n~l;ru rrrnr- rGplnirl. rrnt harArrn<cins intrndurr. alieu rln~nnto- TLr .ruinr eutLm• Iraz nL<ereed u utwdrrr ,~;wr, intn . fnrci;u rctnpln.m illayinu nf <ucL simrraurirz. PrrLnp< tlir nu•ct un- :9.iu: Bttrk 19f01. In cperinl iu<tunrr<• it n.nnl vrn< c.in~ir cnn-icin¢ nlant nf I6e ;ner Ie~ nrrr<znn tn makr ; mo.a Imnrrrn e . hJ .•:rr:r: ?$_a, X ~-- rm.n -+:note[troploid fnruu ni hnth S. 1nLrternv ^_S=:f, \- .mhirl; Lnd thr Implnid rl;rnumznnm Nt6e S. yrroir+ iu nur-ttou ;Clarum •.:nnplornrut nf S. nn..rr m tLr rclnpla<u; B;-1. TLr• rr<ultinc cinWr Lvhrid ic n-v- it \'. rr•r••:...n:. Vvir.- nll Id:un. whirlt rr- ai'n~ :q; rflrrticr tivtilr allorydolduid wd r.;n .ult :rrn;; wtrrzprruir rrna.rz alrr v:di;larod. t• v-.•d iu 6::rk;-rnc•ivc u i1 pn•<iblr tn :ra=umr incnrrrrtl. thm tLr 2060458002

JO ECO\OHIC SUTA`s'S TASLL V. DlSrdbr RCSIS2AXS RrSroYSL oT SiCGLnLa SfSC1ES. Diaeases ot Tobacco' . a-.rotwnn eLp. An RR BS BA Sp C\ FE FR' GW PM RIi RV TE T]6' TS WF zcavlb x acuminata z z z alata z z s : ameQLwoi amplesieaulia ' a(CLtSii 1 S r Z x attenuata z S benacidesii benthammne x s biaelocii x s Lmmrie:uia x z catlcula s clerelandii z eordifolia r eorvmbosa debne.i x x a a x r exuelsinr r eziqua s r r v z fo)RetlillF I fra4rxns r [ Qlenea S S r Y S Rlutlnoe3 Y I eoudapeedii x x S Roisef r a r r Iueneria a ' inlrulba x I:ni¢Irtiana x x r a 1a1193d0rRi .a r s Ilnelrra IunaiLrnctcnra IunR[florz m s r s r s s manHmL r x mc¢alosiVhun s ' x x u:<vii nesoFLila s ,wctiflorn x nudieoulis x s s r omidentalia x r x otuDhora z r z palmesi • x z paniculata [ s a s pauciHorc r oetunioides r n1ulTbapalf0lia l ,r r rximundif r s s rrpanda x a r z z r I'' z .oaulata s rutundifnlia rurtiu S z S Saaderae (8crt•) z I i utcAelffi x s eimulans z sotanitolia Rarzinii ektanii X t Letter s>mhols and the discaee mhich the. :imiennte are es toRowe: An e Anthncno.sc. RR = Black root rot, BS = Bleck ilunk. BU = Blue mold. SV = Brmm epot, CN = Cpst nematcdv, FE = Frcpepe, FW = Fuserium trilt GSC = Gnnville .•'ilr, PM v Pomlery nlilde••, RE. = Roat-kuot nemntodes, RC = Rattle virus. TE - Tobecco etch rirus, TMV = Tobaceo musaic .irus, TS = Tnhaeco etreak rirus, antl \CF = tCildfire. 2060458003

TRE GE\tl$ \ICdet3\A TABLE 1-cmi0inued 81 Sirorianu app. An RR B5 331 Sp CS FE FA' GW PM RE RL' TE TSR' TS wF suavealeua x s x x z sl'brostris z tabacum x z x x I z thyrsiflora tomentnsa z z x z tnmentoaifurmia x z x i triROnopbylli x x umbratiea ' undulata x x x x velutiaa v: z z z ,,iRnmlioides x x product is a v;ilid hybrid. For these reasons, tve have purposely not cited references to al- legedly fertile Fr intetspecific hybrids or re- ports based on the use of mixed pollen. It is important to remember that interspecific hcbrids are usually mm•phologically inter- nirdiatc with respect to their parentnl spe- riec and nre most often completely sterile. \Cheit sterilitv hurriers have hren nserrowe and a fertile Y. tnbnrmn-like product with d$ -hrommnmes hns been obtuined- the product often represents an :rlicn sub- stitntion race. equivalent to Iiolmes Sam- snmr or siniilaz alien anbatitutinrt roces oh- tained by Oka (1961). Such rnces have 23 psit< nf 1'. tn7tncnm chrpmoamues and 1 chromosome pair from the disease-resistant spcries parent. Alien substitution races do not represent a successful conclusion for an interspecific breeding objective. Tlrep must be repeatedly hackcrossed. selfed. and se- lected until a line is nbtuined which s ves llendclian segregatian for tlte disease-resist- ant faetor; for then. and only then- hns the rnrnmosorne segment, bearing the disease- rpcisimtce fnrtor, been translorared to a 1-. Inlmrum chromosome. Also, desirable ge- nrtie rharaeteristics ronnot he transferred via interspecific hybridization unless the.- Po=sess sufficient dominance to he expressed in the Ft and in each succeeding generation. Tobacco Diseases and Possible Sources of Resistance Tobacco Breeding and Disease Investiga- tions, Crops Research Division, United Stntes Department of Agriculture, maintains I cnllection of over 1000 fonns of S. tn- bncnm_63 of the 63 recognized species in the m germs, as well as a number of fertile intet'specific hybrids. Variant fonns of the species are also maintained. The 63 spe- cies mentioned above subscribe to descrip- tinus provided by Gnodspeed (195}) for the snb-geuera Ruateen. Tnbactrnry and all of the Prn.ndr,idre except those of the section Suurrolents where the information provided hc Burbidge fl®G0) is followed. in an attenipt to classify this collection as n 1@?etTotr of useful gerut plasm, this re- port provides a guide based on publications iu vvhich various 1-irnrnnru species have been shown to be disease resistmtt. ]Iajor dis- c:ues of tobacco with letter symbols based on their covutmn names (Table 1) and the Slcotiorur species resistant to them are listed without any attempt to distingvish betlveen degrees of disease response. The source of the pubtication. ho.vever,' is indicated so that the nri,,innl report ntnp be consulted for specific details. For Table 1 the more neutral desienation "resistant" vns judged preferable to sev- erat classes of resistanre because uf the oh- vious impossibilitp of equating tests of dis- ense response from one pnrt of the world to another. Even nt a single location, it is often possible to encounter diRerences in eRective- ness of artificial epidemics, in physiological strains of the pathogen, and even diHer- enees in collections of host material: conse- quently, n resistant response in a species re- lated to N. tnbncum merely trepresents a po- trntinL. Its utilizntion depends on a nuniher of conditions. The wost iutportaut of these requires that tlre resistant response is ex- pressed as a dominant; i.e., resistance must he detected in F, hyhrids to permit further steps in the interspecific breeding procedure, 2060458004

ECONOMIC BOTA\L luthoritp tmmes for the Sirotiana spe- cies were obtained from Goodspeed (1954), except for the section Srrnreolentes which subscribes to the report of Burbidge (1960). Host names not cited in the text are Y, so- Imtifolia Nalp., 9. benaciderii Goodsp., X. thyr,<iAora Bitt. es Goodsp., N. stockiotii Btnndeg., \", au,eghinoi Speg., S. longi- bracteata Ph., \-- miersii Remy, S. corym- bosa Remy, \', linearis Ph., V. spegazzinii \fillan., S. umbroticrr Burbidge, A". nmplez- icnufis Rnrbidgr. ;md \". mnritimn Wheeler With the exception of S. amegbinoi and N. longibracteata, whiclt are knomn from herbarium samples onl}•, the other species listed in Table 1 are currently maintained in the Beltsville collection. duthority names for the disease-produc- ing organisms were obtained from two sources: Index of Plant Diseases in the Cnilcd Srntex. Agr•icultural Handbook -165, Crops Researeh Division. :lgricul- tural Research Service, United States De- partment of Agriculture, R"ashinv on. D. C., 1960; and Lueas, G. B.. 1955, Diseases of Tobacco, The Scarecrow Press. Inc., \ em l ork. AYTHaAC.\'OSL (An.) CofIetotric)rnnr spp. Sources of Resistance: ]icGrew (1952) described two levels of resistance among 42 Sicotiana species. Un- der those with moderate resistance he listed Y. rrigim {Cheeler, S. Aniglrtiaun Gnodsp., :\". gianca Grah., S. goodspeedii Wheeler, Y. nesopLifa dohast., S. occidentafi.r Wheel- er. and V. repanda Willd. The species which exhibited a higher level of resistance were S. afata, S. debneyl, F. ImrgsdorBii, S. iongiliora, S. nndicaufis Wats., .7`. syI- rrnrris Speg., and Conies, and \"- trigono- pnylla Dun. In addition to the resistsnt species listed by )IcGrew, Debagh (1957) found that N- megafosipfion Heurck and Jfue11. and N. pabneri Gray were moderately resistant. Raeber and Cole (1963) studied the disease response of a number of species and classi- fled one group as field resistant and the other as seed bed resistant. Those with field resistance were S. alata, S. glance, S. langs- dorfii, and Y, rylrestria. ^licotiana deb-' nryi, Y- fongiflnra, Y. uudicaulis, and Y. sanderae (Hort.) were resistant under seed bed and field conditions. The strain of S. sanderac which Raeber and Cole tested was very highly resistant to anthracnose un- der Southern Rhodesian conditions, and they suggested that i, forgetiana HorL es Hem- sley, a progenitor of N. aattderae, also mimht be checked for resistance to mildew. Indi- vidual collections with higher levels of re- sistance might be obtained from those South American centers of origin (Goodspeed 1934) mwhere the 9-chromosomed members of the section _tiatea are endemic. BLACK Roor aor (RR) Thidariopsia basicola (Berk. and Br.) Ferr Sources of Resistnnee: All of the black root-rot resistant tobacco varieties in current use derive their re:ist- ance from S. tabacum sources. Variability of the causal organism and methods of breeding for resistance huve been discussed bc Valleau (195?). According to Clayton (1953), the S. tnbocmu source of black root-rot resistance is pol}•genic, whereas the resistance he obtained from S. drbneyi is monngenie. Black root-rot-resistant breed- ing lines with the monogenic source of re- =istance are currently being evaluated in this lahorutorp. Other sources of resistance in the metms nmp be found in Y. lorgijforn, .l". ealgua, \", gossri Domin, and S. pani- cnlatn L. Resistance frotn these and other sources moc hnve value in the event that rnces of the pathogen virulent to the 5. debnryisource are discovered. BLACK SH.1\F: (BS) ' Phytophthora pnraaitica Dast. var., nico- tiniae (Breda de Haan) Tucker. Sources of Resistance: . . Among the 51 species which Lnntz tested in 1957 for resistance to black shank, ti. fongifiora, S. pAnnbaginifolia, and the pu- mila and brasilia varieties of N. rustica L. appeared to have sufficient resistance to warrant their cansideration as possible sources of resistance. Transfer of a resist- ant factor from N. plumbnginifolia has been reported by Chaplin (1962) and Apple (1962). The inheritance of a resistant fac- tor from 3'. fongijlora has been described by Valleau et al. (1960). Most varieties now in use have resistance 2060458005

TSE GENUS \IGDTtdti• derived from the orio nal Fla. 301 breeding line developed by Tisdale (1931). This re- sistance stems entirelc from N. tu6acum. Other X. taLucum sources of resistance have been found from time to time. The most re- cent one is Beinhart 1000, a selection from Quin Diez, which has an exceptionally high level of black shank resistance (Hea euad and Lautz 1957). The difference in response of F~ hybrids with Beinhart 1000, and sus- ceptible tobacco varietiesand Ft hybrids in- volving the Florida 301 source of resist- ance, was not statistically significant (Sil- ber and Heggestnd 1963). Black shank re- sistance in certain selections of S. tabacum appears to be partially dominant, although modifiers tend to elevate or depress the re- sixtant response. BLIE.lIOLD (BJI) Pevmm.porn }abacinn ddam Sources of Resistance: -alumst all of the .\-lrntinnn speeies in the section Sum•eofrntea are resistant to the blue mold or,"nism. This section represents a heterogeneous array endemic to Australia and it.e nearhv islands. According to Wark (1963), the blue mold organism has exerted selection pressure on the rnrious mewhers of the Snareolcntes during a large part of their eenlution. Wark's evaluntion nf re- sistant species is in close agreement with the more limited studies of Smith-White et a]. (1963), Ciayton (1945), and Hill and . Mandryk (196?). . The following species appesr to be the uwst resistant in tests conducted by the above-named authors: N. debneyi, N, rvigsa, Y. fieaperfs Burhidge, N. ingulbq Black, S. rosulata (S. Moore) Domin., Y- sbnulana Burhidge, Y. suaceoiena Lehm., and S. rdutina Wheeler. Wide ditferences in the blue mold response of various collec- tians of these species would suggest that . careful evaluation should be made before . any are selected for hybridization. Narlc's ~ comments on the genetic nature of the re- sistant sistant mechanism should be consulted. ~ BfiOtYN SPDT (Sp) " 3lee+nnria longipn (Ell. and Ev.) 3feson '- Sources of Resistance; i Two reports dealing with brown-spot re- ; sistance appeared very recently. The work b3 of von Rantm and Lucas (1963) and that of Raeber et al. (1963) agrees in most'partic- ulars concerning the difficulty of assesaing a resistant response. Both groups of workers agree on the resistance of N. anareotena. In addition, von Rannn and Lucas indicate that S. forgetiana and S. ocridentolia are resist- ant, while Raeber and his associates provide evidence for moderate resistance in Y. longi- flora and Y. velutina. CrsT SEU.tTUUes (CS) Hetrrodern tnbnnun Lownsb. and Lmrn<b. and two undescribed species; Osborn's and the Horseuettle cyst nematodes. Sources of Resistance: Unpublished data provided br L. I. ]lil- ter, Plant Pathologist of The Tidewater Re- search Station, Cirghtia Polytechnic Insti- tute, Holland, Cirginia, and A, F. Schind- _ ler, Semntologist, formerly of the Crops Re- search Division, United States Department of Agriculture, Beltsville, 1laryland. indi- cated that the following N(cntimm species nmy he tentatively classed as non-hosts: S. a[ftma (scnonymous with \'. nlnta), Y. ntaCn. N. arrrtaii, S. peuntioides (Griscb.) ]Iilan., Y. rrpanda 1Cilld., and S. tomento- silan.~is Goodsp. The cyst nematode has been known in Con- necticut for about ten years (Lownsberry and Lownsberry 1954) and is a localized problem in Z irgtnia at this time (Miller et nl. 1962). If this disease should spread, it may be advisable to attempt the interspe- cific transfer of disease resistance from those species described by Miller and his co- workers. It may also be advisable to test species related to the resistant ones as N. undulata and N. wigandioides-ancestral forms of Y. arentaii. Other members of the Tomentosae-N, tnmentosa R. & P., and N. otophora Griseb.-might also be screened for resistance. FnocErE LE.r Szor (FE) Cercospora nicotianae Ell. and Ev. Sources of Resistance: Although frogeye leaf spot is widely dis- tributed throughout the major tobacco-pro- ducing countries of the world, there is very little published information nn sources of resistance. The recent paper by Raeber et al. (1963) indicates that 13 species within 2060458006

34 ECONOMIC RoT.\T the subgenus Petunioides were moderatelv resistant. A high level of resistance was found in a strain of N. debneyi and in P. rrpanda. In addition, the amphidiploid hp- brid 4N (Y. repanda X S'. sylrestris) was also highly resistant. FCRARIVY WILT (FW) Fusn.i,un orysporiurn (Schlecht) Wr. var• nicotlmta< Johnson. Sources of Resistance: Strain dilferences in Fnsarimn oryspor- inni var., nicotinnae complicate resistance breeding. Z"alieau (1952) took note of this rariability and indicated that suitable sources of resistance would have to include a level of resistance or immunity that would be effective against the many strains of the pathogen. In S, tnbnctnn, manp varieties have rarious levels of resistance and the Turkish or aromatic t}-pes appear to he rir- tuallp immune (,lrmstrong 1947). First generation hpbrids between resistant and susceptible tobacco varieties are usuallr in- termediate. This supports the cnntentiau of Clayton (1953) that resistance to fusarium wilt is polygenic. -A. comprehensive screening of the numcr- ous Sicotimm species and variants Fhould he made in order to determine whether or not monogenic dominant resistance or immmritv to fusxrium wilt call he found. GRA\r14E WILT (GW) Psevdomwras solmmcranon E. F. Smith Sources of Resistance: The major source of resistance to Gran- ville wilt is attributable to the selection T.L 448A, an isolate from over 1000 collections of `-. tabacum obtained from Mexico an•1 South and Central America (Clayton and Smith 1942). Clayton (1953) describes re- sistance from N. tabaeum as moderate, and indicates that it is polygenic in inheritance. The work which followed the discoven• of T.I. fl-t8A produced many breeding lines. Hybridisations and selection within these lines served to develop such highlv success- fui flue-cured varieties as \C 95 ~Moore et aL 1962). Since the first uilt-resistant va- rietp, Oxford 26, was developed in 1935, a number of wilt-resistant varieties were re- leased from time to time. But each in turn was replaced by another because, unlike tiC 95, most either did not have resistance to other important diseases or lacked commer- eial quality. In the course of these breed- ing procedures, the polygenic recessive mechanism for resistance, originally derived from T.I. 448A, was undoubtedly altered by modifying genes. Potvnrats \Itt.aeW (PM) Eryaiphe efehoracearum D. C. Sources of Resistance: The amphiploid hcbrid Digluta, with rr- sistance from the .P. gtntinosa parent, was used by Ternovsk}- (1934) to develop tn- bacco varieties with a dominant form of re- sistance to powdery mildew. In addition to \-. glutinosa, Ternorskc fouud that .\. acn- nrirrntn (Grnh.) Hook., N. nlnra, \-. bige- locii. fTorr.) Wata., V• fra,nrans Honk, Y_ lnng.edor/fii, S. lungiAora. S. nortifinrn Hook•, 5. nvdicaulis, S. paniculata. y, plumboginifolia• S. repnnda, S. >mrdrrnr, and Y. nmreoiens were also resistant. ap- parentl.-this source of resistance is not ef- fective against powdery mildew in Southern Rhodesia (Raeber et al. 1963). Rnssouw (1963) was able to transfer c resistant re- sponse front d'% glutino,m to N. mbncnm, The resistance sccros to be a hypersrnsitive ; rellctLUn. RoSSouw dl5o found resistance in . S, aeuminata, S. aiata. S. attrnuntn, S. brurhmnimtn Domin., and S, debnrvi. Rce- her (1863) tested a large assortment of Sir- ntlnnn species and found the following to be resistant: 3'. aaaninata. \-• drbnryi, N. rr- crL•ior Black, d'. erigrm, S. glutinosa, Y. good.epeedii, S. go,esei. S. knigbtiana, V.-. Iangadorfii, S, neegalosipLon, S. nnd'o- canll.e, S, ocaidentalia, \, palmeri Gray, N. pauriflorn Remp, S. raimmndii Machr., .l'. rrpanda, 9• sanderae, N. trigonoplrylla• and Y. rehreirta. In addition to some of the spe- cies listed above, ]farcelli (1950) found that N. glauca ami Y% tamentosa were resistant to powdery mildew. Resistance in N. tabacum was discoveredd b}- Wan (1962) in the Japanese air-cured., varietv Buo-fan. In S. tabecum. re.sistance is controlled by two recessive genes, in cau-• trast to the dominant response derived from Y. glutinosa, Raeber's (1963) disappoint-, ing result with N. glutinoaa has caused him to shift his interest to the type of resistance fnnnd in 1'iuo-fan. It would be interesting 2060458007