الفهرس | Only 14 pages are availabe for public view |
Abstract 1) Four isolates of Botrxtis alU1 were isolated from neck rotted and aJ.so from neczo ta,c blighted leaves of onion plants collected from different govettJOrates of Egypt. 2) bee d1ffezent isolates we:re virulent to both bulbs and tmnapla,nts. Also an assooiation of neck rot and leaf blight or spott1.ng was observed. 3) leaf spotting occurred on onion plants sprQ’ed with the f11 trate of J:. J,lJil! grown on Dlltrient bro tb. dextrose l1.q~ mediumwbile the oultural filtrate of onion extracts gave oontinous blotch”. A s1~1cant; ~lation between growth temperature and viJ.’ulence was found. At the same time the fungus grown at opti8ln temperatuxe (20 00) produced the highest number of leaf spotting. b highest number of spots occurred also on plants sprayed with filtrates of ftJDgt18 grown atp pH 4.3 - 5,2 as it gave best rate of growth. Iesponse of wounded potted plante to fUDge) filtrates was not affected by various incu.ba’tion ~rlods, However, six days incubation gave lDfIxhnUID mte of growth. There WJ.8 a high positive correlation between amount of growth of isolates and their v1J’.’u.1e:oceon the fo 11age• - 92- 4) .s vim, screening of :Benlalie, :Bavistin, ~psinR 50, Ba.S3050, plantvax and ,J)1tbane II 45 on j. §lli1 :revealed that Benlate, Bavistin and· TopsinR.50 were the most effective fungicides i.J:lhibited mycelial growth, sporulation, and sclcrotial formation at the concentration of 1 ppm. Inhibi tion of mycelial growth and sporulation oocurred at 100 or 200 ppm of plantvax or :.IU.thane M45 respectively .• 5) High PG activities _re assoOiated with all isolates .filtrates. Bani-Buef isolate (the most virulent) gave the highest ax and Pl4E activities, while Gisa isolate (the leQ.8t virulent) showed decrease in OXand PIlE activities. 6) .AlUgb. percentQe,e reduction in pectin v1sooaity by cu1tural filtra.tes was obtained at 20 °C (the optimum . tempero.ture for fungal growth). CellulalJA activity showed sim:1lar results in addition to a high cormla:tion between temperature degzee a.nd enQlDe activity. On the other h:Jnd, HIE shone~ to :...emo~ active af 1.0 - 15 °0 •. 7) Poq@iQ.lf’..Otur..i:lQS9 (?G) prc’:uc’tion wo.s greatq reduced in culture by arJdi ng certain fungicide. to tbe medium. Be.nla.te, or .J)i..thaneeffectiveq inhibited PG - 9~- production in cu1ture. Oncontrary, plant’v:»x showed ver;r little effec~ in :tteducingPGproduction. Adding ’BenlD.teor plontvax to tbe mediwn consiaemb~ X’edaoed BlE p1’Oductlon~ Oellulo.se o.ctivit1’ was reduced in filtrates of j. gll1i wae~ )~tvo.x ortithane II 45 .•• incorporated in the filtrate. 0311u1aBe activity was little affeoted bY’adding Eenlate to the fil1im.te. Adding different concentrations of Benlate, plantvax and DLatha.ne II 4-5to the fungal £iltratea did not .reduce PG o.ctivity, However adding Benlate or plantvax to the filtrate affected HIE aDtivity to some extent. 8) Pec”tinmetb3’leB’tro.se.Po~galactu.rono.se. and cellUlase activities 118m aasocia..ted 1d..th onion bulbs aDd leaves infeeted with B-. a-WJ.. production of BQ.i:, PGt aDd ex en.,mes •• mom a.ctive 1n infected tissue than in haa:l’t~ ones. Inc1’9o.se _s obVious 1n PGfollo_d by ax, while a slight inc.J:.’8l18nti no’ted for J’IE,. lelative activities of PG, ax and PIlE in the onion blighted leaves wexoe greatq increased than in the ~al~ ones. 9) Isolatea ditf’e:red in peroxidase utiUr.Lt,. in botll myce J.1um. and cul.tuJ.’O.1 filtrate. G1.sa i801.o.te~_d the most actiw pexo.x:ld,.,. in ’t.be t’t1nga1 IQ08lium wbile amnd-.e~isolate •• mo%8 uti:ve ’than other --- ~~ - -_..--,_ ...._-’. ---- _. - _.._--”, _.- -_.- ----------~~- --- --- ---~- -------- ~--:-, 1 - Q4..-- isolates in cultural. fi1trates. Also tbe isolates varied in activity of phenol oxidase in myoel1Q1Il and cul~ filtrate. Peroxidase and phenol o~dase a.ct.iN’1-17.Lea W9re more in the myoeUum.than i.n the fUtm,-te-. 10) No diffe1”eD.OO in pel.’Ox1da.se o.ctivity was found in bao.ltby bulbs of transplants ot ~b_ed go~den (less susceptible) and Giza 6 (swtCeptib~) onion varieties. ,Actin ty of pheno1 ox1dase in ~br1ed golden 1188 more than 1n Giza 6 in bea.1tby bulbs of transpl..-o-. It; was found that tbe i.D:feotion with -B” allU incren.seJ the activity of tbe t1io en~s. in both tested vn.rie ties. 11) stu.03of inoculum. poten1iial in gree~bDUSe indicated th¥t in.creosing the iDoculum amounts Of -B. a~ rEIsulte d in an ini ti..o.l l.1Dear increase in the disease incidence • 12) Benlate (at 2%) and :ea.v1.stin (at 5%) gave a. cample ta pmteot1on of neck rot iDfection in pots while Topsin R 50 (a.t.5%) redueed tl:ae infection. ~3) vcr1atol mo.cti.on to infeotion ld.tb .I- .aJJ-:i.! iud1-eo.ted that twelve onion varieties WBL’8 sU808p’tible to irdeot1on. !Ibe de~ ~ disease reaction ranged :from ---~- _._. ------- _._-- ._.- - - - _._. --- ._-- ,--- _. -_ ....~ I - 95- 75 to 100 %. Hybried goldetl. and H. tropieana sho’Wed the least percentage of infeo:ti.on. 14) IafIuence of irrigation on neok rot in the field and storage declared that infection of onion bulbs with j. ~ was fo.vow:ed by increo.sing number of irrigation. o.lso the yieJ.d, and average weight of individw11 bulb were increased ~th increase in number of irrigation. ~ percentage of l.’Otted bulbs occurred in. ’tbose wa.texed on.JJ’ once. 1.5) llUect of m.a~i.ty of bulbs on the incidenoe of neolt rot in the field and storage showedthat a. :reduction in pe :tOen’ta.ge o£ infection (iDsgJJ:l fi.oant). yie ld and average weight of bulbs at; the eo.rlJ” l:IaxWsting time, memllidle in storaosi’ immature blllbs we.re more su.scepti. ble to neck rot than the fully mature ’. 16) .Evo.1ua’tionof dipping ,’tmJ18P1tu:lts ODd bu.lbs in certain fungic.i4ea agD,inst neck rot di8ea.se on onion for (bulbs) ond (seed produot1oJ1) undBr field OOnditioDS reveo.1ed that Benlate and Ba.vistin were the most effect!Ye fungiOiQe8 wbils !Jbp1nBSO reduced the percent.o.p 0% i.n;fect:1.on to a. J..ar£9a degree. _.,_. ._.~ .. -_.r-~---~---~-------’----”·~~’··-------’--’----_·.-.--.~~--~---- ... - --_. --- ,,_ .. ~- .._-~- -,... _- ... -”96 - ].7) ~ at sprOJing of Eenlo.te, ~psinR 50, :.mdBavistin can be used as a protective fungicides during storage. !lbe timing of preb.tJ,.rVest applica.tion ho.ve a. slight effee’t on tbe reeponse of bulbs to fungici.dD.l appUoo.- tion. Tba fungicides reduced no.tltttll infection sl1gb.tly while they showed sabstontial inhibition in case of artifioially inocul.o.ted bulbs |