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Abstract SUMMARY The present iavestiJution wns plalTI1ed to study the causal organi~s of sunflower, root diseases, the effect of some physiolo3icnl factors, scprophytic behaviour and their corrtz-o L, The findiIlGs ccn be summarized as follows : 1- Lso Lat Lon of the causal orgc.nisms of sunflower root disease was carried out from diseased roots oollected from Giza Governorate during 1975. Sclerotium rolfsii~ R.solani, ~.ph2seoli, F. fusarioides and other speoies of ~~pergillus. Fusarium, Alternaria and Curvularia were isolated with prevailing of Ill•.phaseoli. 2- PathoGenioi ty tests using Giza-l sunflower variety indicated that -S-.rolfe!! caused foot root, wilt ’ and blight; R,zo.1.an1 ca4sed stunting) M.phaeeoli caused _ ... - -. ’ . :IIi.. . l • ohare 0$1 rot and’ .;.,;;.11~. ~”ioides oaused s1;u.atiDg, thel1 ~Ut. In addl1;i~ -tbe}o~’ tungi’ ca~sed pre- or p-on•• .• ·~~,I ,,’-.’ ,” emergence damping-oft ~ different ratios. ,SC1~o’1. ·;”,.’-1 .”- rolfsii was found to ot!the most a::;:;ressive pathogen than the other lG~._f~l. ’ S.rolfsii + R. sclani increased the infection than each of them alone. 4.•. Solerotiwn rolfsii seoretedo:::o.lioaoi.d, in cU1t~e$. Potato cylinders were 50ft rotted when immersed in S.~olfsii filtrate or. different concentrations of oX8lic acid. Thus, the lOES of coherence was fast in hiGh concentro.tions of tbe acid •. . , 5- Filtrate of S.rolfsii caueed ~o cermination to _._~ sunflower seeds. ~iltrates of the othex fW1gi however, caused drying of seedl~UGs shoots of Giza-l variety after 48 brs., while dried all seedlinGs of Miak variety. B- ~ar~\\U flts$’:10id6S snowed only the b.i3hest cololliza~1on rntl~sJ:~ Wbile,ll.solani was a. po~ ooloa1zero! the ag~:Plate8. __oo].onizat1on rat1~s 1ncr.asec!lgradually ’ith tile i.reese in the amowxt 6- I>ercentac.;& of diseased plants Gradually increased with the increase in ru”””Uountof Lnocukum, 7~ All the tested suriflower varieties W~e found to be s~sceptible t·o the disease. Giza-l vo.riety gave modQa:te re~etenoe ’b$)all f~1 exeepl S.rolfsii. ~ J~ • - .’ - 4 ( ·to1~ to ·.·e..1WM 9- Myc6’licl,r;rowth of the fou,r fu::).::;1 deoreased with increasing the concentr~tions of fU1~icides when incorporated in P,D.A. med1um.Moreover, fU~sioides differ~d in the ooncentrations at wh.l.ch fungal growth was inhitit ed, Bnvistin and Topsin :,~.Y1Grethe best fUQ5icides to ..R••..solro1i, M.phaGeo1i ~d F.fusarioides as . .”- - they inhitited ,:;rowth at lower conccl1tra-~ions, while vitavax/captcn und vitavax/thirarn we~e the most effective fungicides asainst S.rolfsii. .:~-. 10- The four systemic fun3icidesused, remained active in the plants fo:r;-about 3 weeks. Theaefungieides translocated from the seeds and loc ali2led in the root tlfJsuea more than’ in stems or leav.es and gradually dec~ea5ed upw~ds. 11- Seed t-~eatm.l1”fw1th eaeh ()f vitavax/c~ptaa at· O.~ or Bav~st~:a. 0.’ was the. h~n f~ic1d.,: f<Jr ._~:.’ controlling tMdiseasej |