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Abstract -140- SUMLlARY The findings obtained in the pr8sent investigation can be summarized as follows: 1- A survey o~ the stalk-rot diseases of grain sorghum revealed the occuren~e of these diseases in most of the sorghum-growing areas of the country. The incidence of stalk-rots, in fields selected at random in the visited Governorates, ranged from 0 to 20% with an average of about 9%. : ! 2- Three conditions of the stalk-rot complex were observed. Of these, Cephalosporium wilt disease caused by Cephalosporium acremoniwn was the most prevalent. Charcoal stalk-rot due to Macrophomina plmseolina WaS sometimes observed. A third wet stalk-rot condition, frequently encountered, was apparently a modified form of the wilt disease due to infection by secondary invadors • .3- Different local, commercial and exotic cultivars ”.J, of grain sorghum were tested against- infection with stalk- -. rots in naturally intestedfield at Shandawell. It was found that cultivarsG) and NESI007 were highly susceptible ” ------ - _._--- -141- to infection, whereas, G54, L 31/62, L 109/67, L 132/67, L 162/67, NES 635, NES 786, Gl14 and hybrid 113 were hig~ly resistant. ,” 4- The pathoeenic1ty t~sts, were artificially confirmed using both the soil-infestation and the stalk-inoculation techniques, showed that Q.acremon1um was highly pathogenic producing typical wilt symptoms on grain sorghum plants. Macrophomina phaseo1ina was found to be pathogenic producing ,I charcoal stalk-rot symptoms. Fusarium Doniliforme was shown to cause severe root and foot-rot in plants. 5- Studying pathogenic variation in five Q.acremonium isolates demonstrated that all tested isolates were pathoeenic and produced premature Withering of plants. Fayoum isolate was the most Virulent one, whereas Beni-Suef isolate was the least pathogenic one. 6- Cross inoculation of’C.acremonium isolates whether ~, obtained from maize or from sorghum were more virulent to .}, the sorghum varieties than to Q8ize varieties. It was found that all the funeal isolates which were isolated from grain sorghum were able to infect maize PUults producing typical , • -142- signs of tlaclc- bundIe. Likewis e, the grain sorc;hum cultivaxs were shown to be affected with fungal isolates which ’:Jere isolated- from maize, where plant a shoned the wilt symptoms. HO”Jever, no speciali:::~D.tion in pathoeenicity was found in Q.acremonium isolat.es obtained neither fror.l maize hor from sorghum. 7- The resu.lts of varietal resistance to Q.acremo.uiwJ1 showed that infection % by soil-infestation method rax\:::eu frOill 10 to 80 ?~ between thi2 tested cnltJ.’1:.irs. The local variety 31/62, J.J 109/61 and L 132/67 were hiGhly reDhltonL J whereas, local 102/67, L 129/67 and G3 VJCl’C highly sU8ceptible varieties. Toot hpick-inocl.11a tion technique J on the other hellO., showed that culi;~;-”e’l:’s NES 1818, nES 1324 and UES 635 we.re hi~~ly resistant to infection a~d L 102/67, L 129/67, !~brid 113, hyb~id,119, L 2S/62,.;G123, L 109/67, L 162/67. )rES 786 wer e hiChly auacep t LbLe to in:r(~(~tion. 8- Stutlyinc lTe1ation of :,lant nee to infection with -C.a--cr~noniu.m•.....-. revcnld that infection increasod with the increase of plant age 1.U1t 11 t he th:LX’d \”:eek o\: sowinc· -----~-- -- -143- 9- Root injury appeared to faci litata Lnf’ec t ion, in par t Ic uIur at t he late stages of p’ln nt gro’.’Jth. 10- Infection percentage. increased with the tncr ee se of -C. -a-c-r-e-moniurn inocu.lum level t ill it l’ eUcIH” 1 t:18 :naxirnw.l •... when 100 gm Lnocu’Lum per Ho.25 pot were user] and tlten dec- Itned VJi th the inc rease of LnocuLum pot ent :ia 1.. 11- Using the sen!’ pLat e modificatiou of carnbr’ i.dGe Iilethod, it has b ee n shown that £.~E~19n5.l!!11has n moder.ate degr ee of comp eta t tv e sn.prophytic aldlity. by soil mieroorganis!il!’;. 13- Ro inhititory effect of culture filt~0t0 acrem9.!!i.~ to the tested fungi was f’ound , ’FW1’SBS the nafllely; Bacill .•’U..! id.uhtli s, StaJl~.l2.s.occus. ~qureus and 14- C.~~~~BS not active to secr~te pectolytic enzyI,le s , -144- 15- -C.ac.remoniwn was able to hydrolyze otnrch and to Crow on wediurn contuining starch as D. sole source of carbon. Follmving 1~e1son’ s method (1944) for estimating redl”l.cins sugar s , it could be able to find a relation between the variation of pathoeenic:tty of Q.acFemonium and efficjYfloy in starch hydrolysis. It has been shown that Fayoum isolate (the most pathoeenic isolate) g£\ve ”I thu hiehest results followed by Giza isolate. 16- On f’i It er paper t Q.acremoniur.l showed hieh c ellulose decomposine ability. Colorimetric <letermination of cellulose decomposition as reducing sw~ars revealed that Fayama isolnte was rather active cellulose decomposer and Beni-Suef Lso Lat e was rather P90r in this respect. 17- Colonization of buried, sorghum stalk pieces apparently increased with the increase in the amount of inoculum in the inoculum-&oil mixtures. A decrease in the colonization with the increase of incubation time WU:3 noticed. -145- 18- The effeet of two soil factors on the survival of Q.f!.cremOnilUTI in d ecornpos ing Lnf’ec t ed sorghum stalk pieces was studied: ;: ” (i) Temperature: Decomposition was $lower at 20°C than at 30 and 35°0. Survival of the fitngus was greatest at 3D and 35°C than at 20°0. (ii) Moisture: Under four soil moisture levels; air dry, 36.J50 and 100% saturation, it was found that decomposition of infected sorghlli~stalk pieces waS generally faster than that of healthy stalk pieces. Decompos LtLon was greatest at 50% saturation. Q.acremonium survived most effectively in stalk pieces buried in soil containing 30 and 50% water saturation in which the fungus showed increasing act ivi ty after two. montbs and then this activity decLtne d gradually up to 4 months. However, in air dry soil and at 100% , water saturation activity decline4., rather sharpl¥ • -’ 19- On stalk inoculation with Q.acremoni~t deterrnination of sugar content revealed a remarkable decrease in total and non-reducing sugars due to infection. A -146- notico.able increase in the percentage of reducing sugars occur ed in the inoculated stalks with the increase of time from 15 to 45 daY:s ~f ino~ulation. ” 20- Protein cont ent was higher in inoculat ed stalks than that of uninoculated one~. 21- The rate of amino acids was higher in the case of inoculated stalks with .C-..acremonium than that of ’.!uninoculated ones. Total and free amino acids increased as a result of infection after 15 days to reach the maximum at JO days then decreased slightly after 45 days from inoculation. 22- Total phenol contents increased in inoculated stalks compared with uninoculated ones. Amounts of free phenols were markedly high in the inocnlat ed stalks than those of uninoculated ones. conjugated phenols were , high in uninoculated stalks tnan those of inoculated stalks ” particularly in the later stages of disease development. 23- Orthodihydroxyphenol contents were higher in inoculated stalks compared with uninoculated ones. • -147- 24- A noticQ.able increase in titratable acidity in tissues infected with C~acremonium was observed. This ”~ - was mar e clear at 15 days after inoculation. 25- The amount of total soluble solids (r.s.s.) increased in stalks inoculated with Q.~~~c=r~em~o_na_fit_eurm~ 15 days of incubation followed by considerable decline. but amount s of T.S.S. were still higher than those in .. J uninoculntes stalks. 26- Inoculation of grain sorghum stalks with g. acremonium caused an 0 bvious decrease in chlo:r.phylls a and b as well as the carotenoids content of leaves developed from infected plants. 27- StudyinB the activity of oxidative enzymes in tissue extracts revealed that infection ,nth -C.acremonium increased the activity of phenoloxidase, peroxidase • ..’ catalase and ascorbic acid oxidase. 28- Infection with stalk-rots caused a considerable r~uction in the weight or kernels (about 50% reduction) on the basia of dry weit;ht. However, the bulk and true -148- densities were higher in kernels of infected plante than in those of healthy ones. 29- Infection with stalk-rot s caus ad increase in kernel endosperm and reduction in germ Qnd pericarp if compared with those of kernels obtained from healthy plants. 30- A positive corxelation between moistl~e, ash .1 and suear contents in whole kernel was observed. Infection decreased all these cant ent s to a level lower than that in kernels of healthy plants. ,31- Protein cOlltent was generally higher in whole kernel, endosperm and germ of grain of infected plants than that of grain ot non-infected plants. However, ’ results in case of pericarp fluctuated. ,32- Study or protein fractio,ns in seeds of both ~. healthy and infected plants with stalkrots exhibited that kaferin fraction was generally higher in whole kernel of infected plants than that in kernel of healthy ones on contrast with glutelin fraction. The albumins and globulins ” ------------ -149- . were lower in the kernels of infected plants than in those of Wl-infected pl~nt·s. The insoluble proteins were always . . ~ higher in kernels of infect’ed plants then those of healthy ones. ,. JJ- Both of Lysine and Tryptophane were lower in whole kernels of infected plants than those in kernels of uninfected one s , l’ 34- in their ~,i’:- Determination of crude fats revealed a decrease contents in grains of infected plants comparable to fat contents in healthy plant seeds. 35- Determination of minerals content showed an obvious increase in lis, K, Ca, I~ and Fe contents, on contrast with Zn and Cu in kernel flour due to infection. No difference was founl in Mana.gane•.s. e cent e.nt of kernel flour of healthy and infected plants. I”” ~ • I .r |