Adult Plant Resistance of Thatcher Wheat to Stem Rust

Transcription

1 Resistnce Adult Plnt Resistnce of Whet to Stem Rust N R X Nzreno nd A P Roelfs Former grdute student, Deprtment of Plnt Pthology, now reserch plnt pthologist, nstituto Agronomicl do Prhi, Cix Postl, Londrin Pri, Brsil, nd reserch plnt pthologist, Cerel Rust Lbortory, Agriculturl Reserch, Science nd Eduction Administrtion, US Deprtment of Agriculture, University of Minnesot, St Pul Coopertive investigtions, US Deprtment of Agriculture nd the University of Minnesot Scientific Journl Series Pper,6, Minnesot Agriculturl Experiment Sttion The uthors grtefully cknowledge the seed of the progeny lines developed from crosses mde by B Skovmnd Accepted for publiction 7 June ABSTRACT Nzreno, N R X, nd Roelfs, A P Adult plnt resistnce of whet to stem rust Phytopthology 7: No reltionship ws found between the independent Sr genes for seedling resistnce nd the dult plnt resistnce of whet, s mesured by rust severity Pyrmids of seedling resistnce genes Sr, Srl, Srl6, nd did not improve resistnce to stem rust The performnce of some progeny lines with both Srl nd ws similr to 's, nd this suggests tht the fctor(s) involved in the dult plnt resistnce of might be relted to this Sr gene combintion The dult plnt resistnce of ws sensitive to inoculum density Although this chrcter hd been selected successfully under hevy inoculum density t the end of the seson, the resistnce ws most pprent t stge (erly milk) Under light inoculum density, however, the gretest difference existed in the terminl disese severities Additionl key words: Puccinigrminis, rcespecific resistnce Stem rust of whet cused by Puccinigrminis Pers f sp tritici, cn be n importnt disese wherever whet (Triticum sp) is grown extensively The whet cultivr ws relesed in, fter more thn yr of breeding for resistnce to stem rust, desirble gronomic type, nd milling nd bking qulities () resulted from crosses between Mrquis/ Knred, hrd red spring nd winter whets, respectively, nd Mrquis/ lumillo, red durum () inherited the milling nd bking qulities of Mrquis, seedling stem rust resistnce from Knred nd umillo, nd the dult plnt resistnce from lumillo Currently, is importnt in the spring whet breeding progrm becuse it hs dult plnt resistnce Although the genetics of seedling resistnce of ws generlly understood, the genetics of its dult plnt resistnce ws not The vlue of dult plnt resistnce in protecting whet cultivrs ginst stem rust hs been pointed out by Stkmn nd Christensen () They stted tht breeding for resistnce ginst individul rces of pthogen would continue, but every effort should be mde to combine ll chrcters in single cultivr tht conferred some degree of generlized resistnce ginst the pthogen Brennn () stted tht breeding progrm should develop rust resistnt cultivrs with resistnce conditioned by severl genes, nd since rcespecific nd rcenonspecific resistnce exist in whet, both should be used The objectives ofthis study were to determine: the reltionship, if ny, between rcespecific seedling resistnce genes nd dult plnt resistnce, nd the effect of inoculum density (7) on the dult plnt response susceptible in the field to prevlent US stem rust rces, wheres hs been rted from modertely resistnt to modertely susceptible under the sme conditions Reltionship between seedling nd dult plnt resistnce of The presence of resistnce genes ws postulted (7) by inocultion with four rces of stem rust The rces were chosen on the bsis of virulence or virulence on lines possessing the stem rust seedling resistnce genes of (Tble ) Sevendyold seedlings of the progenies, the prents ( [C ], Prelude C, nd Brt C 67), nd of the "single' gene lines SrR (C ), 6ASrg, Srl6R (C ), nd Line R (Srl) or BtSrlTc (C 7) were inoculted independently nd evluted for infection type (6) dys fter inocultion The lck of rce virlent on Srg mde the detection of this gene in the progenies impossible Purity of rces ws verified by using set of "single" gene differentil lines, nd stndrd inocultion techniques (6) The term "single" gene line is used to refer to host line tht hs only the designted gene pir for resistnce to the whet stem rust fungus popultion tht occurred nturlly in the United Sttes Gret Plins during the pst yr After inocultion, seedlings were plced in dew chmber ( C, drkness, nd % reltive humidity) for pproximtely 6 hr The chmber ws then illuminted (, lux) for hr, the temperture ws grdully incresed to C, nd the dew dried slowly Seedlings were then trnsferred to greenhouse (pproximtely C) supplemented with, lux light when dylength ws less thn hr The Prelude/ siblines were plnted sidebyside, in MATERALS AND METHODS n investigtion of The study ws divided into two prts: the first, with the tresistnce of reltionship of the dult plnt rbrt rcespecific seedling resistnce genes Sr, Srg, Srl, Srl6, or, known in ; nd the second, field evlution of the sensitivity of resistnce to inoculum density Both studies were performed in F 6Fs singleseedderived genertions of Brt/ ( siblines), nd Prelude/ ( siblines) crosses, nd on the prents Brt nd Prelude hve been t my be freely This rticle is in the public domin nd not copyrightble The Americn reprinted with customry crediting of the source Phytopthologicl Society, TABLE nfection types produced on "single" gene lines for the seedling in, nd on, Prelude, nd resistnce genes known to occurwith certin rces of Puccinigrminisf sp whets when inoculted tritici Rces HJC MBC RBC TDM nfection type produced 6 g ; ; + neffective on "single" Sr gene line or cultivr Tc Prelude Brt CX CX ; CX ; CX CX t > C, in seedling tests Vol 7, No,

2 duplicte field nurseries, t St Pul nd in Ech sibline occurred once per loction in m row, m prt There were eight replictes of Prelude, nd two ech of the "single" gene lines, Pd, 6ASrg, Srl6R, nd BtSrlTc, mong the progeny lines ws used to seprte the replictes nd test lines; there were replictes of per loction The Brt/ siblines were plnted similrly, but the Prelude ws replced by Brt, nd the "single" gene line for Sr by Bt At, row of Brt ws plnted perpendiculr to nd m from, the upwind end of both progenies to provide more uniform inoculum source Disese severity ws ssessed t to 7dy intervls, beginning before uredi ppered in the plots nd continuing to crop mturity Severity rtings were bsed on the modified Cobb Scle () Disese prevlence ws % except t the beginning of the seson when uredi per row were counted The Romig growth stge scle () ws used to record plnt development Dt were nlyzed by regression nd mens were compred ccording to the t test () Effect of inoculum density on the dult plnt resistnce of The experiment ws the sme s previously described The est centrl Minnesot loctions were t St Pul (hevy inoculum density) nd (light inoculum density) The hevy inoculum density ws obtined when winter whet nurseries were inoculted weekly (strting t bout stge ) with mixture of representtive US stem rust rces Airborne spores produced on susceptible lines in those nurseries were the source of inoculum in both yers t St Pul nitil infection t resulted from nturlly occurring irborne inoculum, nd primry infections ppered wk or more lter thn t St Pul Lines selected in represented the rnge of severities nd NO NOJ BN A obtsrltc xbtsrl6tc so D NO J 6 7 n Prelude & Brt uprelude ABrt Dte 7 Brt 7 7 F OG Prelude ABrt 6 obtsrltc xbtsrl6tc " Prelude *6A Sr g e Pd *6A Sr g 7 e Pd genotypes for seedling resistnce These lines nd the three prents () comprised the 7 experiment When possible, lines were chosen tht were similr in mturity The experimentl design in 7 ws the generlized rndomized block with two rndomly ssigned replictes of tretments within ech of three blocks The two reps/block element ws introduced to clculte the block X tretment interction in the nlysis of vrince () Ech replicte ws m row, 6 m prt from the next row A m row of ots (cultivr Stout, C ) ws plnted between the rows to reduce block X tretment interction Ech block ( tretments X two replictes) ws plnted in two prllel rnges seprted by m lley The long xis of blocks ws plnted perpendiculr to the previling wind direction, to reduce inoculum movement mong blocks Seven m rows of Stout ots, m prt, seprted the blocks At both loctions, susceptible whet spreder row (Brt) ws plnted upwind, m from the blocks Stem rust ws ssessed t dy intervls from the initil infection to crop mturity Anlysis of vrince nd test of hypothesis of the dt were done (,) noculum concentrtion ws estimted through the 7 seson by cumultive spore counts t both loctions Uredospores were collected from windoriented rod impction trps (,7) locted in stem rust resistnt blocks, pproximtely m from the experiment Trps were chnged dily t St Pul nd ech fourth dy t The plnting dte t ws erly in the recommended period for the region; t St Pul it ws ner the end of the period so tht the potentil for inoculum buildup ws enhnced Ech stem rust rce identified from collections mde in both yers nd loctions ws virulent on Sr, Srg, Srl, nd Srl6 7 7 Dte 7 7 CLAX Dte Fig Whet stem rust progress curves for: A,B,, nd "single" gene lines Pd, 6ASrg, BtSrlTc, nd BtSrl6Tc, t St Pul nd, in, respectively Dt re mens of,,, nd replictes of the "single" gene lines, respectively, nd of C, D,, Prelude, nd Brt, t St Pul nd in, respectively Dt re mens of,, nd replictes, respectively E,F,, Prelude, nd Brt, t St Pul nd in 7, respectively Dt re mens of 6 replictes PHYTOPATHOLOGY

3 RESULTS The stem rust progress curves for, Prelude, nd Brt, t St Pul nd, re shown in Fig C nd D, respectively The disese progress curve for Prelude ws intermedite between those of nd Brt The resistnce of, s mesured by severity, ws esier to distinguish t the beginning of the epidemic from Prelude or Brt thn when plnts were ner mturity t both loctions hd terminl severity s high s % (Tble ) n 7, the inoculum density ws higher t St Pul, s shown by the cumultive urediospore count of 7, spores per squre centimeter t St Pul, nd,7 spores per squre centimeter t The prents responded to stem rust in 7 pproximtely s they did in (Fig E, F) Prelude ws intermedite in response between Brt nd, except on the lst two reding dtes t St Pul, when Prelude hd severities similr to Brt (Fig E) Differences in severity mong prents nd the test lines (Figs le nd ) were gretest when prents nd siblines were pproximtely t stge on July Even though Brt rusted more severely t St Pul, there ws no significnt difference in terminl rust severity between loctions in either yer (t = NS, df, P>, in, nd t = NS, df, P >, in 7), however, responded differently to inoculum density The verge terminl rust severity in, for t St Pul, ws significntly higher thn t (t = 6**, 6 df, nd t = 6**, 6 df, for on Brt/ nd Prelude/ blocks, respectively) A t = **, df, for the sme comprison in 7, indicted tht rusted significntly more t St Pul Prelude lso ws sensitive to inoculum density, with the terminl severity t St Pul significntly higher thn t in both yers (t= **, df, in, nd t = 76**, df, in 7) The "single" gene lines used s checks, Prelude, nd Brt hd susceptible ("S") field response t both loctions throughout the seson, wheres ws modertely resistnt ("MR") to modertely susceptible ("MS") Ner the end of the 7 seson (stge 6), Brt ws rted "S", Prelude "S" to "MS", nd "MS" to "MR" n the nlysis of vrince for rust severity t growth stge nd Reltionship of seedling nd dult plnt resistnce of The stem rust progress curves for the "single" gene lines nd re shown in Fig A nd B for St Pul nd, respectively The terminl rust severity of the siblines, grouped by seedling resistnce genes possessed, re shown in Tble Most groups behved similrly t both loctions s indicted by the t vlues; ie, differences in terminl rust severity of the siblines were not significntly different ( P > ) between loctions The susceptible prent Brt responded similrly Terminl rust severity for the siblines tht hd both Srl nd, nd for nd Prelude t St Pul, differed significntly from those t (P < for the siblines, nd P < for the cultivrs nd Prelude) The field response to stem rust of the "single" gene lines for Sr, Srg, Srl, nd Srl6 ws similr t both loctions, in contrst to the response of (Tble ) At, stem rust developed fster on 6ASrg erly in the epidemic thn on the other "single" gene lines, but terminl severities were similr for ll lines Bt, Pd, nd BtSrl6Tc rusted slowly t the beginning, t, but reched terminl severities over 7% Stem rust developed slowly on Srl6R t St Pul; however, this line hd semiwinter type of growth (it remined t stge 6 while the plot verge ws stge ) Effect of inoculum density on the dult plnt resistnce of Terminl rust severity of the prents nd most "single" gene lines ws greter t St Pul thn t in (Tble ) Terminl rust severities of the siblines were regressed ginst loctions The regression coefficients for Prelude/, b = 7, nd for Brt/, b = 6, differed significntly from b = (t = 6**, df, nd t = 7**, df, for Prelude/ nd Brt/, respectively); therefore, differences existed between nurseries One of these differences ws inoculum density (hevier t St Pul) Climtic dt suggested tht the environment ws fvorble for rust development throughout the seson t both loctions TABLE Whet stem rust resistnce genes, popultion size, terminl severity t St Pul (hevy inoculum density) nd (light inoculum density), nd the t test of the loction men comprison, for Prelude/ nd Brt/ progenies, prents, nd "single" gene lines in Postulted No of Sr gene(s) nd checks Sr Srl lines or replictesb Terminl stem rust severity St Pul Men Rnge Men Rnge 6 No of t vluesc lines or replictesd 6 Terminl stem rust severity St Pul Men Rnge Men Rnge 6 6 Sr6 Sr, Srl Sr, Srl "" Sr, Srl, Srl Srl, Srl6, Sr, Srl, Srl6 "" Sr, Srl, 7 6 * Sr, Srl6, 6 " Srl, Srl6, t vlues' * Sr, Srl, Srl6, None Prelude Pd Brt Bt 6ASrg ** ** ** '" BtSrlTc Srl6R Bsed on modified Cobb Scle () bprelude/ progeny 7 c* nd ** = P < nd P <, respectively dbrt/ progeny Vol 7, No,

4 t mturity for St Pul, 7 (hevy inoculum density) nd terminl for, 7 (light inoculum density), the block X tretment interctions were not significnt (P> ) in llcses This suggested tht the ots plnted between replictes decresed the movement of inoculum There ws greter vribility mong terminl severities t thn t St Pul in 7 (Fig A, C) Differences t stge were not detected in becuse only trce mounts of disese developed in the field Rust severities t St Pul vried more between lines t stge thn t the end of the seson (Fig B, C) Terminl rust severity on ws not different from tht on Prelude or Brt t St Pul (Tble ) Under conditions of hevy inoculum density s mny s nine of the siblines were not distinguishble from either the resistnt or susceptible prent, s indicted by Duncn's multiple rnge test of significnce (P>, Tble ) Rust severity of, however, ws different from tht of Prelude nd Brt t stge (P<), nd seven siblines were sttisticlly similr to The severity of Prelude ws not different from tht of nd of siblines behved similrly to under low inoculum denisty (P > ) DSCUSSON The rcespecific seedling resistnce genes Sr, Srl, Srl6, nd, of were postulted in the progenies Results of erlier studies indicted tht Sr(,) nd Sr () re not relted either to the dult plnt resistnce of or the slow rusting chrcter of Er whet () This study indicted tht, unlike A, the progeny lines tht possess only Sr, Srl, Srl6, or, regrdless of the susceptible prent involved, hve similr disese response under different inoculum concentrtions (P >) is gene chrcterized by "C" to nd "X" seedling infectiontype on, by rces virulent on Sr, Srg, Srl, nd Srl6 One progeny line with rusted significntly more thn (P<) Thus, this study () produced no evidence tht ny of the Sr genes for stem rust resistnce of re independently relted to the dult plnt resistnce s determined under different disese intensity in the field t hs been proposed tht pyrmiding rcespecific genes would result in generlized resistnce greter thn the summtion of the specific resistnces due to ech gene () The dt from lines with genes Sr, Srl, Srl6, nd were grouped into vrious combintions of,, or There ws no evidence of incresed resistnce in lines with combintions of the Sr genes n most combintions, unlike tht in, the mount of disese ws similr between loctions (P>) Sometimes, the smple size ws too smll to support sttisticl inferences (ie, combintions of Sr, Srl6, nd nd Srl, Srl6, nd lines) The only lines with combintions of genes tht performed like were Srl nd in both crosses Some lines with this genetic combintions rusted more t St Pul thn t (P<) Erlier reports showed tht the dult plnt resistnce of ws inherited by two complementry recessive genes (,6,,,) t is possible tht is locted on the sme chromosome s Srl, nd tht some of the fctors responsible for the dult plnt resistnce of re locted between these two genes There were Srl, lines more resistnt thn in the Prelude/ cross Skovmnd et l () reported tht Prelude possessed some genes for slow rusting which in combintion with those of must hve rendered some of Srl lines more resistnt thn The occurrence of Srl lines tht rusted more severely thn, however, showed tht the dult plnt resistnce of ws not due to these genes per se (severity t stge ) Brennn () identified genes on 6A nd B chromosome substitution lines of, tht, independently, cuse reduction in number of stem rust pustules Brennn's results contrsted with those of others in tht they indicted tht the dult plnt resistnce of, s mesured by receptivity (), or by TABLE Whet stem rust severity t erly milk (stge ) nd t mturity t St Pul, nd t mturity t, for the prents,, Prelude, nd Brt, nd selected siblines, in 7 : W t > Postulted genotype, or cultivr, " ) G *, W,, V = U C M,,, M = LNES Fig Whet stem rust severity in 7 for the cultivrs, Prelude, nd Brt, nd selected siblines: A, Terminl severity, t ; B, At growth stte (erly milk), t St Pul; nd C, Terminl severity, t St Pul PHYTOPATHOLOGY Srl, Stem rust severity St Pul Stge Terminl Terminl Sr, Sr, Sr, ib gh fgh efg 6 Sr, Srl, Srl6, efg d None' Srl, Srl, None Sr Sr, Srl, None Srl, Srl, Srl6, Prelude Brt i efg h b def fgh cde 7 6 e cd d b f d b cd Trce d d d d d d 6 b Trce d 7d Trce d d d bc d c d d Severity = % bsed on the modified Cobb Scle () brust severity vlues followed by Duncn's multiple rnge test of significnce (P < ) 'No Sr genes for seedling resistnce were detected in the greenhouse experiments

5 rust rting in the field (,6,,) is due to complementry Hyes, H K, Ausemus, E R, Stkmn, E C, Biley, C H, Wilson, recessive gene pir f only two genes, s proposed by Brennn (), H K, Bmberg, R H, Mrkley, M C, Crim, R F, nd Levine, M N re involved in the dult plnt resistnce of, then the 6 whet Minn Agric Exp Stn Tech Bull pp hypothesis of hving one of them locted between Srl nd is Hyes, H K, Stkmn, E C, nd Amodt, S nheritnce in unstisfctory, becuse Srl is known to be on chromosome B whet of resistnce to blck stem rust Phytopthology :7 () 6 Koo, K S, nd Ausemus, E R nheritnce of rection to stem The lesitc lck offcreli correltion betweeo between the dult nd the Thedling rust inagron crosses: of Timstein with, Newthtch, nd Mid J Am ther dulto plnt pnt resistnce resstrncend tesoc seedling resistnce genes of lso ws demonstrted by 7 McVey, D V, nd Roelfs, A P Postultion of genes for stem rust line without the genes Sr, Srl, Srl6, or tht responded resistnce in the entries of the th nterntionl Winter Whet similrly to t growth stge nd t mturity t St Pul Performnce Nursery Crop Sci :7 in 7 All lines were infected erly in the seson, so the response MrtinezGonzlez, J M S 7 Slow rusting to Puccinigrminisf of this line ws not due to disese escpe sp triticiin Er whet PhD thesis University of Minnesot, St Pul responded differently under different inoculum pp densities in these experiments The wide vrition of stem rust Nzreno, N R X 7 Adult plnt resistnce of whet to response of in the field, which is influenced by the mount stem rust MS thesis, University of Minnesot, St Pul pp of disese pressure, is illustrted by the difference of pproximtely Puccini Netby, grminis K W type of infection triticithe whet ofseedlings by in the greenhouse s on mesure percentge nd % in terminl rust severity of between St Pul infection in the field Sci Agric :66 (hevy inoculum density) nd (light inoculum density) Netby, K W, nd Goulden, C H The inheritnce of in nd 7, respectively Stem rust rces occurring in both resistnce to Puccini grminis tritici in crosses between vrieties of yers were virulent on ll known seedling resistnce genes of Triticum vulgre Sci Agric : t C The difference in rust severities t Nelson, R R (editor) Breeding Plnts for Disese between yers ws due to the reduced mount of exogenous ResistnceConcepts nd Appliction Pennsylvni Stte University inoculum rriving from the southern USA (A P Roelfs, Press pp unpublished) Pn, C L A genetic study of mture plnt resistnce in spring whet to blck stem rust, Puccinigrministritici,nd rection to blck n, ech line occurred once in m row plot djcent to chff, Bcterium trnsluscensvr undulosum J Am Soc Agron nother line Thus, if resistnt line were between susceptible lines, :7 the inoculum generted by the ltter my hve ffected the Peterson, R F, Cmpbell, A B, nd Hnnh, A E A inoculumn density nd the disese response of the former, mking digrmmtic scle for estimting rust intensity on leves nd stems of selection success low Nevertheless, resistnt nd susceptible lines cerels Cn J Res (C), 6:6 were selected in, bsed on terminl rust severity nd rust Roelfs, A P, Dirks, VA, nd Romig, R W 6 A comprison of severity t stge 7, t the hevy inoculum density loction These rod nd slide smplers used in cerel rust epidemiology lines were retested in 7, nd they proved tht the selection ws Phytopthology : successful 6 Roelfs, A P, nd McVey, D V 7 Low infection types produced by Puccinigrminisf sp triticindwhet lines with designted genes for t is possible tht inoculum moved redily from row to row in resistnce Phytopthology 6:7, nd resulted in incresed rust severities on some lines n 7 Roelfs, A P, McVey, D V, Long, D L, nd Rowell, J B 7, terminl rust severity on one line ws 7%; however, with Nturl rust epidemics in whet nurseries s ffected by inoculum some isoltion in 7, it ws % n 7, rows of ots plnted density Plnt Dis Rep 6: between the test plots tended to reduce the plottoplot movement Rowell, J B, nd McVey, D V7 A method for field evlution of of inoculum This conclusion is supported by the nlysis of whets for low receptivity to infection by Puccinigrminisf sp tritici vrince A nonsignificnt block X tretment interction term Phytopthology 6: suggested tht, mong other fctors, the inoculum produced on Sheen, S J, nd Snyder, L A 6 Studies of the inheritnce of susceptible line did not move in sufficient mounts to msk the field resistnce to six stem rust cultures using chromosome substitution lines response of the djcent lines Yet, hd s wide rnge of of Mrquis B, whet selection Cnnd J Genet Cytol R 6:7 Skovmnd, Roelfs, A P, Wilcoxson, D The terminl rust severity in 7 s it did in reltionship between slow rusting nd some genes specific for stem rust LTERATURE CTED Brennn, P S Generl resistnce in whet (Triticum estivum L) to stem rust (Puccinigrminis Pers f sp tritici Erikss nd Henn) PhD thesis University of Ssktchewn, Ssktoon pp Clpouzos L, Roelfs, A P, Mdson, M E, Mrtin, F B, Welsh, J R, nd Wilcoxson, R D A new model to mesure yield losses cused by stem rust in spring whet Minn Agric Exp Stn Tech Bull 7 pp Green, G J, nd Dyck, P L The rection of whet to Cndin rces of stem rust Cn Plnt Dis Surv : resistnce in whet Phytopthology 6: Skovmnd, B, Wilcoxson, R D, Sherer, B L, nd Stucker, R E nheritnce of slow rusting to stem rust in whet Euphytic 7:7 Stkmn, E C, nd Christensen, J J 6 The problem of breeding resistnt vrieties Pges 6 in: J G Horsfll nd A E Dimond, eds Plnt PthologyAn Advnced Tretise Vol Acdemic Press New York Steel, R G D, nd Torrie, J H 6 Principles nd Procedures of Sttistics McGrwHill, New York pp Wilk, M B The rndomiztion nlysis of generlized rndomized block design Biometrik :77 Vol 7, No,