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Abstract -SU-M..•M_A-R-Y~ Pruit rot diseases are the most serious diseases that attacking strawberries in ARE, causing considerable losses in guantity and quality of 7ield. The present investigation was planned to study : a) The causals of fruit rot diseases. b) SCDe physiological and. pathological studies on Ph.ytophthora cactorum. c) Enzyme activities in both culture filtrates and in un-inoculated and inoculated fruits with l.cactorum. d) Chemical constituents of un-inoculated and inoculated fruits with -P. eactorwn. e) Host range of Z•.C•,;.;8•C•••t•..O••r••.um,;a;n;d strawberry cuIt1vars . resistance. f) Bftect of some 1’uDg1.cides oil l.cactopn in laboratory and leather rot disease in greenhouse •. Results obtained can be summarized as follows : 1) Four fungi namely; PNtophthora cactorum (Leb. &: Cohn.) Schroet, Botptis cinerea Fers. ex-Fr., Rhizoctonia ( Cort:l.c1um) solam (Prill & Delacr) Bourd& Gals and RhizopuB nigricans (Ehrn. ex-Fr.) Lind. were isolated fran infected fruits of four straWberry cnltivars collected from different governorates in BgJpt;However, l-caetorum was isolated for the first time in Egypt and it was isolated also more frequently than the other fungi. - 128 - 2) Pathoginicity teats in laboratory revealed that all the tested fungi were found to be pathogenic to strawbe~ frui ts with different degrees. However, l.cactorum was the most virulent fungus in both pre-mature and mature (wounded and un-wounded) cr strawberry fruits. 3) Results of PhysiologiCal and pathologiCal studies on ~.cactorum could be summarized as follows : a) CDA mediumwas the best media for mycelial growth and number of sporangia, anther1dia and oogonia. Whereas, v-a jUice mediumwas the best one for Oosporea production. b) The optimum temperature for fungal growth was found, to be 25°0. minimumand max1mum temperatures were 5 0c and 35°C respectively. In this respect, sexual reproduction was favoured by low temperatures on contrast with ase%Ual reproduction • C) Glycerol, galactose, ratinose and dextrose did not permit any growth of E,.cactorum when each was used as the sole carbon source in the medium. Similarly, sodium nitrate or nitrite, ammonium. sulphate, ammoniumnitrate or chloride, urea and gelatin were un•..favourable tor l. cae torum. growth and did not p~2’Dlit any growth when used. as sale nitrogen source in the medium. - 129 - d) Highest sporulation (sporangia) was found at 80 % R-Hand oospores at 10C % RB, while no mycelial growth was noticed at 14.5 and 50 % R.H. e) The fungus, !.cactorum, had a wide range of hosts in Egypt. It infected fruits of tomato” appl-e., leiloB., ~ve1 orange and potato tUbers, however, with different degrees of sympt:”GIIS.. and disease severity. f) The effect of infection with Eocactorum on strawberry fruits revealed that inoculated fruits contained. high amounts of dry weight than un-inoculated ones. In this respect, Aliso (less susceptible cur tivar) gave higher dry weight in both inoculated and un-inoculated fruits on contrast with Balady ( the most susceptible cultivar) cUltivar. g) The percentages of infection with ..I.caetOM increased with the increase in WHO ( Water -lIDitl:f Dg - CapeCi:tT”). All fruits that tOUchedthe soil were infected with l.cactorum. 4) Strawberry fruits of Balady cultivar were the mOst susceptible to infection with the tested fungi, whereas Aliso frui ts were the least susceptible and ..riogs and Fresno were :~derately resis1antto infection .However, ~ection . was less in the pre-mature fru1 ts than in the IDB.ture ODeS in all tested c~~ivars. =’ .. 130- 5) a. PME, PG and ex enzymes activity increased by prolonging of incubation period of inoculated and un-inoculated :f’ruits and also by increasing time of rese tion fran 5 to 60 min. at 30°0. However, the actiVity of these enzymes was higher in Balady (most susceptible) ~ ’least susceptible) cultivar .• than .Aliso b. Polyphenol oXidase and peroxidase enzymes activity increased by increasing the incubation periods prom 2 to 6 days, and, also in inoculated fruits than un-inoculated ones. ”, ,,’.”.(.’ i : ” H~’;’~ve;, Aliso (least susceptible) cu’LtivaJ; contained higher enzymes than Balady (most susceptible one) • 6) Soluble carbohydrate contents were higher in inoculated frui ts with !:.cacto~ than in un-inoculated ones especially atter 2 and 4 days. Total sugars reached its maximumafter 4 days then decreaced again. However, Aliso (least suscepteble’ cuI tivar) showed the lowest amount of reducUJg sugars at,ter 2,4 and 6 days, on contrast with Balady (most susceptible one). In this respect, non-reducj,ng sugars increased in Aliso cu1tivar, on contrast with Balady one. 7) a. Qualitative analysis of free amino acids proved the presence at 17 amino acids i.e. Cystein, Lycine, Histidine, .’\.spartic acid, Serine, Glycine. Glutamic acid, l’heronine. Alanine. Proline, Tyrosine, Treptophan, Methionine, Valine. Phenylalanine, Leucine and Iso-leucine of all straber17 - 131 - cuI tivars in un-inoculated and inoculated fru1 is with ~.cactorum. b. Also, quantitative analysis indicated that Balady cu1tivar contained higher amounts of free amino acids than Aliso one. Moreover, total amino aCids increased in strawberry fruits inoculated with ~.cactorum. 8) a. Total phenol content increased in fruits inoculated nth l.cactorum compared with the un-inOCulated ones. However, Aliso cultivar contained higher amounts of total phenols in both inoculated and .un-inoculated fruits than Balady one. Similar results were obtained as regards free phenols and ortho-dihydroxyphenols. b. As for conjugated phenolsJ their amounts increased or decreased during the development of disese with no general trend f or all cuI t1 Vat’s. 9) T.S.S. contents increased in strawber:ry fruits of different cultivarsinoculated wi th~.cactoram. c01lpared with un-inoculated ones. 10) Titratable acidity increased by prolOnging incubation periods in un-inoculated fruits compared with the inoculated with 1-9actorum ones. - 1)2 - 11) a. -In-v,itro· studies, ’Benlate, Bavist1nand Tecto fungicides gave best control against l_cactorum on PD4medium. While, Hespor, Difolatan were intermediate in th.eir effect. In this respe’ct the following fungicides 1.e’., CClDazin Daconil 2787, Dithane» 45 and Topsin]l were les8 effective. b. In greenhouse, all the abovementioned fungicides were effective ·n controlling leather rot (l.cactorum) and Daconil 271!rT t Dithane 1445 and D1folatan were the most effecti ve.1’uDg1cides.’ Bespor, Gom.z1n and Bavistin were le8. e~e~~ive.On’the other hand, ~enlate, !opsi~.and Tecto ~re intermediately effective. c. UDder field condi tiona.,i t was found that among nine fungicides, Docoml 27Ent Dithane M4e5 and D1folatan gave the best control of fruit rot diseases and gave the highest yields during the two seasons 1979 and 1980•. ,\ - |