الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
reacti.on•’the res1lJ.t8obte.1n8d cQU1.dbe s
zedin 10118foU.O’Wi,ng :,_ ~ ••WIlberof fUllgaJ. iBol.e.t••••showed e. ,,14. epect~ ofvirul-encelevelS. It waSnot possi.~· to d•••1•&11&’·such iSolates ••••dUferent races bSCalJlleof the l.-lEof differentiaJ. lin ••••with known geneUc compaeiUS.
2- CCOIlPIlX’W resiSt””,t and sU8cepti~e cotton vsri.e1il”
in both the ”hesl;tb;J” and ”diSeaSed” C(Dd1ti.OIllI111.respect to lIlidn0 acl4 compollition indj.c.ted that Ie.)
At early at,.gee ot plant grOWth. :zoot canteD’ll oflIIIlinoacids willialJDOIItidenticaJ. in both r881B\-
and susceptibl.8 healthy p~an:tsl then clecrea8e4’With age and to a greater extent in the 8U8~roots. As a. reeul t of infection, higher levelS
of free amino acids were experienced with 1’OOt8 ofthe susceptible variety and continued to increaeein rel.atio~ to healtb1 tiSsues as the disea.ee p~ogressed.Although some degree of reduction i.n ejhinoacids occurred in the roots of infeoted resistan~variety at early stages, their !evel maintained a60 % lllcrease over the healthy tiSsues at l.ater stag •• •The most consistent change was ’the increwa8 in theooncentration of cystine in the resistant varietywhich ’WIIS reported to affect the production of~aric acid. Someother amino a.cids changed in
concentration as a result of in:fection; however,theJ.r ro:le 1.a\mel-ear exc~pt for tryptophan whichcou1d have some bearing on III synthesiSb- J1,2aOet .iaiJ,.a;r reaul.ts. witll some di:ffe:renQes, were
observed for the aminoaoid contents of stems· Total
aI3 well. as certain amino acids increased as a result
of infection. The degree of variation was :lesspronounced for leaf tiS sues. Few aJDino acidsincreaeed in leaves of infected suso.epti~8 variety,
whereas aU. but tryptophan decrea.aed in the resiStantTariety.It appears difficuJ.t to rel.ate the type of p~ant
reaction to any given aJDi,no acid in the heal-thYtissues • ~e ohange in certain aJIlino acids triggered
by in:fection o.o111.dbe one of the key
detet’!l1inante of the outcome of hoet-P8%’aS1te interaction.
In other words, resistance mq not be a
preformed but rather an induced state.
,_ With respect to sugars t different organs ot differentvarieties exhib1 ted both Q.ualitative and quantitative
differences in BUBarcontent. Sucrose, gaLactoee andglucose were pr08ent in aU. organs of both susceptibleand resistant varieties, whereas maltose was only f0UD4J~ -~----_.~.- .. ’in stem tissue,.( c:n the other hand, fructos e was onl.7
found in different organs of the susceptible variety •
.Asa result,.’ of 1n:fection, sugar contenta deer.as ed
Iin roots of both v~i.et1est with galactose + glucose
remaini ng at almost the SaJIle concentration in the
suscept1b~e variety; however, they inereseed in the
resistant one. On the other hand, sucrose decreased
in the susceptible and increased in the resistantvariety when comparedwith the respective contltols.
fluch change8 in sU«ar levels could have aOlfe hea~
on the nutri tiou of the invading fungus either dir.c~
on indirectly and indicate certain metabolie changes
in carbohydrate metabolism due to infect1c.n.
Other p~ant organs responded somewhat diftereatly
from roots wJ:tl:l respeot to certain sugars. As to the
stems, sucrose allowed a.much more increase in the
resi.stant variety than in the suscept1b~e one. On the
cantrary, galactose + gJ.UOOS8 increased first and th8i1
decrea#3edupon infection of the ausceptib1e variety,
whereas they were always Leas in the resistant variety
subjected to ~ect:lon whencomparedwith the respective
healthy oontrols. As to leaf tissue, no change occurred
in the level of sucrose 1n the resistant variety,
whereas it increased in the ausoeptib.1.e one. On the
contrary, a marked decrease in the level of gaJ-actose
+ gJ.ucose followed the infection of the suscep’tibl.e
variety and the appoait8 was true for the resistant
variety.
4- With respect to phenol.ic compounds, three major groups
i.e. mono-, d1- and poly-pheno~s were found in both
varieties. The di-and pol.yphenol.s were present in
comparable concentrations in the healthY org~ of both
resistant 8lld susceptibl.e var1e’t1t1Js. Uponinfection,
these two groups of phenolS increased in orgaJl8 of the
sUBcept1bl.e variety, whereas the opposite vas true, in
most cases, With the resistant one. .Aa to the memo...•
phenoJ.a, the two varieties exhibited comparable concentrations
in roots and 1eaves at early stages and in
st8J18 at relatively later stag.. Following infection,
the susceptible variety alwa;ya exhibited a DROP in the
monophenoJ. ~evel compared with the healthy tissues,
whereas the opposite was mostly the case for the ~reaiatant
variety - Such interconve1.”8iona of phenolic SUbstances
couJ.d be accomplished by the eneymes ot the pathogen and/
or the host in . response to infection. and the 1I:ype of
phenolic compotmdsthspredominate: could play a roJ.e in
determining the type of host reaction as these compOt1nds
differ in their toxicity.
5- With respect to certain hydrolytic en~eaJ 1_.1.:. pectic
and celluJ.o1ytic enzymes, comparative studies shoved
that:
a) Healthy tissues of both 8usoeptible ana. resistant
varieties containe4 some activity of PMB’but none
of the pectin degrading ~,m.ee. Upon infection,
80me increase in PU activity occurred; however,
to greater extent in the susoeptible than in the
resistant variety. On the other hand, the pectin
degrading enzymes were not found except in the
infected susoeptible tissues_
b) Very low activity of cell~ases vas found :in the
healthy t1eeue8 ot both rea’istant and SUBcepti.bJ.e
-varieties. In:fection was usu.a1].y followed by some
inorease in acti.v1ty i however, to a greater extent ion
the susceptible variety. The magnitude of increase
was relatively low to warrant major role ot these
enzymes in pathogenesis.
6- Oertain oxidative enz.ymes,i...!- po~yphenol oxidase,
peroxidase, catalaSe, and ascorbic acid oxidase were
studied in various host-parasite ccabinations• ResUl-ts
obtained coul.d be sYDJrnar1zed as followS :-
a) With respect to PFO, comparab1.eactivi.ty was found,
in most casee, in the healthY susceptible and
resistant varieties. As a reauJ.t of inf action, the
enzYDl9activity increa.8ed in root tiSsues of both
varieties; however, to a greater extent in the
8uscept1bl.e one. At later stages, the activity in
the two varieties w~ not too muohdifferent. In
.1I.om -tiSsues, siJDilar situation was found, except
that the acti.vity in the resiStant variety maintained
a somewhathigher levu than ”the control at laterstages- The Emhancedactivity of PPOin the roots
of infected susceptible variety could account for
the oxidation of phenoliCS to non-toxic polymeric
substanoes ~ead;ng to the production of the brownish
p1£sD81lts characteriStic of vascular diScoloration.
On the other hand. the J.:!Jnj.ted1.ncreelie 1.nPFO
fC)Ulld1.nresistant tiSSUes IIl8Y result 1.n a ~ow
Qld.dation products such 8IJ \I.”unotUIS”,bich are
highlY reactive end more toxic. SUChproducts could
a1Jlo ,nbibit the enzym•••••thus pertiaUY accountiD.!l
for the lOWactivity level. obServed· ~herefore. 1’1’0could have a varied effsot 1.nthe host-parasiteoODlb>nationdependmg on the extent of <>xidatiCRl
effected.b- AS to the peroxidas •••• , it was fC)Ulldthat their activity
”,as enhanced fol.l-owing:lJ1fection in roots of
both susoeptibl.e and resistant varieties. Later.
such activity DROPpedin the former bUt continuedto increase in the ~atter. SUChcontinued enhanced
activity of peroxidas ••••in the resiStant variety
could be one of the determinanta of such. r~\le;
hOWever.it is dUficult to pinPoint the affectedprocesses sinoe peroxide/ites have quite a varied
effect on different vi.taL processes.
c) AS to catale/ites. it ”’e/itfound that infection resW.ted
in an mereslle in their aotiv1.ty m both varieti”.
with the magnitude of increase being h#gher in theres1Stan:’G variety.
d- l!’or ascorbic ac1d ox1daIOe, the increase in a.ctivity
in response to infection wall higher 1n roots of thesusoeptible variety, whereaf;l the rlifVerse was true
for stems. ’rh1a enhanced activity in ”the stems of
resistant tissues coUld exert a drainage effect on
the concentration of ascorbic acid, thUS l.owering
the reducing power and ~dering the phenoli.o compoundS
maintain their oxidi.zed toxic form. Furthermore,
such an en’!;Y’JDSeIld other ox1da.tive BIl’!;Y’JDmBs;y8p:J..ey
a roJ.e in the reoxidation of NAID?Hproduced through
the modified metaboJ..iSmariSing in response to
infection.
7- Jbpl.oying the eJ.eotrophoretic techniQ.ues in polyacry-
:l.am1degeJ..s, certain enzymeswere studied in extracts
of healthy and diSeased plants aI3 well as in extracts
of fw,gel iso).ates. ’rhe following results were
obtained:
a) NOdifference was obServed beiiween the healthy sUScept1bJ.
e and resiStant varieties as to the peroxidase
activ1ty or the isozyme patte:rn- AJ3 a result
of infection, the l.evel. Of activity inereased ’e)
as evidenced by band width and staining density.
The magni-tude of increase was greater in the ausceptib~
e than in the resistant variety. Anactivity
band corresponding to ”that found for the fungal
peroxidae e appeared in the d1Seased extraots. The
multiplicity of peroxidase iso~es was not evident
with pyrogal.lol as the substrate, unless ’the activity
was too low, thus preventing the coalescence of
bands.
b} With respect to esterases, ten healthy cotton
varieties showeda high degree of similarity 1n
their isozyme pattern. Stems were more active than
roots. SimUarly J nine f’lmgal isolates were aimUar
in their esterase pattern, regardless of their virulence.
Whena susceptible and a resistant varie”ty subjected
to ~ection vere oompared, it was found that healtbY
roots of both varieties exhibited similar patterns;
however, the level of acti.vity DROPped as the plants
grew older. Oomparing diseased with healthy extraots,
the former was alw8¥s poorer in activity as judged
by the band staining density. AJ3 to the stem tissues,
healthy extracts showed a high degree of simllar:1ty
in both resistant and susceptible varieties; however,
there was an indication of an additional band in
the former. No consistent trend of change wasfound in reepons e to infection except that thediseased susoeptible tissues maintained theuo seteraae
activity at later stages whlle the corresponding
heal.tby tissues were almost devoid of such an activity.
The role of esterase in disease physiology is
unclear at present; however, it appears to have a
val-us aI3 a diagnostic too~ in view of the high degree
of s~arity in isozurme pattern amongciifferent
cotton varieties and a,lso aJIlong different fungal
isolatese
8- Certain groupS of growth regUlating substances were
studied in both healthy and diseased susceptible cotton
varietiese The results are summarized as follows :-
a) With respect to auxin activity, as judged by the
extent of root fOl.1llation in cowpea seedlingS, it
was :found that infection resulted in a state of
hyperaUXinJ’i however, to a greater degree in the
suscept1bl.e variety part1eu1.arly at the early stages
of disease deveJ.opment.
b) With respect to gibberellinS, 1t was found that
infection led to a reduction in the activity of
th1s group of compounds;however, the magnitud6 of
reduction waa greater in the infeoted susceptib~e
variety than 1n the infected resistant onee This
could Part1aJ.1Y.,tccount for the stunting Sympt~..---- __
oharaoteriziDB;the wllt disease.