الفهرس 
Material and methodsOnly 14 pages are availabe for public view
 |  | from | 130 |  |  |
| | | from | 130 | | |
Abstract
SUMMARY
Onion is one of the most important crops in A.R.E. Through
the growth period, onion plants have been attacked by some
pathogenic fungi. Sclerotium cepivorum Berk. which causes
white rot of onion is oDe of these injurious fungi. It represents
a great problem because of the reduction in the area of
the crop production.
The present investigation was carried oub in a trail to
control the disease by means of chemicals, a :ltagoDistics aDd
testing som~onion wltivars for resistance ’;0 white rot disease.
The results can be SUmmarizedin the followi,lg :_
1) Three different isolates were isolatecL from three different
Governorates aDdwere identified as ~tro”t1um cepivorum
Berle.
2) The three isolates were designated as Isolate No. I from
Tamia (El-BsyoUDlGovernora’te), Isolate No. IJ: from Shandawil
(Sobag Governorate) and Isolate No. III troll lIallawi (El-11inia
Governorate).
3) Pathogenicity tes’ts were carried’ ou’t against transplants
of Giza 6 II in 1984/1985 and 1985/1986 seaso~s.
A.11 isolates were pathogenic, aDd t~ varied in their pathogenicit.
Y from 100% infection in season 1984/1985 (Iso. No. II) to
13•.’0 in season 1985/1986 (Iso. No. III).
4) Ten onion eva 11&IIel.y: Baria Pertozwe, Ben Shellen, Texas
Grano 1105 Y, Texas Grano 1030 Yt Texas GraDO 1025 Yt Texas Grano
- 89 -
502 prr, American line (male sterile), SbandawLl I , Giza 6 14
(improved Giza 6) and Giza 20, were evaluated against the most
virulent: isolate of S. cepivorum (Iso. No. II) to determine
seed germination and their reaction uDder greeahouse conditions.
The tested evB did not varied significantlY io seed germination
and the highest percentage of seed germination was obtained with
American Line (male sterile).
5) The ten onion ova were tested for their reaction to §..
cepivorum Ln 1984/1985 and 1985/1986 seasons uDder greenhouse
conditions using the most virulent iso late. American line source
was the least susceptible one in the two seascns, while the highest
percentage of white rot was obtained with Texas Grano 502 prr
and Ben Shem evs respectively.
6) The effect of 7 fungicides namely: Ulisan, Rovral,
Benlate, Ronilan, SUm1sclex, Bavastine and Daconil on linear
growth of §.. cepiv01”Ull;was studied on PD4 medium. The mycelial
growth of §,. cepiTorUJIwas complatelJ’ inhibitEd at 2.5 ppmBenlate,
Bavisitin 8I:ld8Umisclex, 50ppa RoDilan ElM 200 ppmRovral
and Ulisaa. respectively. While Daconil reducoedthe liDear
growth of the palhogea but ~celial growth Waf’ not inhibited
c01iplete17 at 2500 ppa. Bumisclex, Benla1ie aId Bavistin were
the most effective fungicides, while Daconil 1’0 the least ODe
in this respect.
7) The effect of dressing seeds of Giza 6 II, with three
sys1ieaic fUDgic1de8 ~17: BeDlate, RoDil8J1!LDd SWI1sclex, aDd
two DOD 8781;8_C 01188 oa.13: llUsaIl aad RoY.Joal, was s’tudi ad
- 90 -
under greenhouse conditions. A.ll tested funE!lcides increased
percentage of seed germination except Alliso and Rovral at
the lowest rates comparedwith control.
8) The effect of seed treatment fungicides 00. percentage
of white rot disease was studied uDder aItificial inoculated
soil using tbe highly virulent isolate. All tested fungicides
increased percentage of bealtb3 seedlings as comparedwith the
untreated control. Also. the percentage of bealt~ seedlings
increased as the rate of application increased except Benlate
and Sumisclex.
9) The effect of different rates of somefungicides as
seedling dip methodon white rot disease inci1ence at four
periods of growth season was studied uDder gzoeenhouseconditions.
All tested fUngicides significantly decreased the percentage of
infection with white rot at different periods of onion growth.
Sulllisclex was the superior on controlling the disease whereas
.A.11is&wI1as the least effective fungicide.
lO)Antagonismbev-een the rbizospbere isolated microflora
(baateria. ruag1 and actinolVcetes) from rhizospher of onion
plants aDd !. cepivorua was s’tudied. Results were recorded as
free pathogen zooe which differed according to the ti_ of inoculation
of thepatbogen aDd the antagonist. The hipst inhibition
zone was obtained with Hellliatho!poriu! ap. (Iso. No. 10)
followed by IIn’otbec1ua sp. aDd Aspergillus s:~. (Iso. 50_ 2).
Inhibition ZODe did not obtaiDad with all !fri,:hod.~ i80la1;es
- 91 -
and Penicillium sp , (Iso. lio. 13) and Helmir.:thosPoriumsp ,
(Iso. No.9). All Trichoderma isolates gro\ll over covering
the pathogen and inhibited it completely when inoculated 48
hours before the pathogen.
11) The saprophytic behaviour of the pathogen §.. cepivorum
was studied using two methods, (a) interaction on agar
plates am. (b) competitive sapropb3tic ability.
12) Five isolates of Trichoderma, and Streptoffilces sp.
isolated from onion plant s rhizospbere, 1. !La.rzianumand !..
viride ~ere Used for oniOI1 white rot biocoatrol.
The lowes’t percentage of infection with white. rot (0.0%) was
shownusing mixture of Trichoderma sp. (Iso. No. 19), aDd
Streptollllces sp. (Iso. No. 23). On the otbe,[”band I.. harzianum
and ~. virid, gave the hi:~hest percentage of infection with
rot (15.0%, lO.~ respectively), although thAt” were superior
on control.
13) CbaDgesin chemical components assl>Ciated with white
rot infection in five onion CVS,i.e. AmericuA line sterile.
(the least susceptible). Texas Grao.o.502prr (’the highly susceptible)
aDd Giza 6 II, Giza 20 aDd ShaDdawiJ.I the local varieties
which showed modera’te susceptibility, wnre s’tUdied to deteradDe
the qU8.lltity of total aiDO acids, pl.nolle compoUDds
and. sugars.
- 92 -
14) Phenotypic differences in resist~lce to white rot
disease amongthe five tested CVS,i.e. Ame:d.canline (male
sterile, the least susceptible), and Giza 6 K, Giza 20 aDd
ShaDdawilI, the local varieties which showl!tdmoderate susceptibility
were evaluated at ages of 60, 90 aDd 120 days from
transplanting. Data on sugar contents, phellolic compouads,
total anino acids t percentage of infection ilDd, degree of infection
were subjected to analysis of variallce. The estimated
values of Gar (OVS)t 62 phenotype and berit.lb1lity estimates
for the studied characters showedthat geQ81;1cresistance could
be existed amongeva of onion and large numbermust be tested
under different environmental conditions. ::t seems likely that
both free phenols and total amino acids con1;ributed to varietal
resistance.