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Abstract 114 SUMMARY 6. SUMMARY Citrus is one of the most important fruit crops in Egypt as well as in many countries of the world. Citrus plantations are widely distributed in Egypt for local consumption as well as for exportation. The obtained results from this work could be summarized as follows: 1. Eleven fungal isolates were isolated from diseased Navel orange fruits collected from Egyptian wholesale market, different retail markets and from orchards of different Governorates, i.e. Giza, Menofeia and Kaluobia. These fungi were purified and identified as Geotrichum candidum, Cladosporium herbarum, Thielaviopsis pavadoxa, Phomopsis citri, Alternaria citri, Alternaria alternata, Nigrospora sp., Penicillium digitatum, P. italicum, Alternaria sp. and Botryodiplodia theobromae. 2. All the isolated fungi proved to be pathogenic to Navel orange fruits. Penicillium digitatum, P. italicum and B. theobromae were the most pathogenic fungi. Meanwhile, G. candidum and A. citri gave moderately infection. On the other hand, Nigrospora sp., A. alternata, Phomopsis citri, Thielaviopsis paradoxa and Cladosporium herbarum were the least pathogenic ones. 3. Trichoderma hamatum, T. harzianum, T. legonarum and T viride isolated were used for the biocontrol in vitro and in vivo for the causals of fruit rots incited by A. cz.r.rz, B. theobromae and G. candidum. a. In vitro experiments: The effect of culture filtrate of the bioagent fungi on growth of the three pathogenic fungi demonstrated their growth was affected to different degrees. The highest to c effect was produced from one-week-old culture of T.viride, hamatum and T harzianum isolates. The growth of the fungus candidum was completely inhibited with the three tested conce trations (5. 10 and 20%), with exception of the culture filtrate 0 T. legonarum. Also, the concentrations of 5 and 10% reduced the growth of A. cirri to a large degree, while the concentration of 20% completely inhibited the fungal growth. Culture filtrate of the tested concentrations minimized the growth of B. theobroMae, especially the culture filtrate of T hamatum, which gave the highest effect. The same trend was observed by the two and three weeks old culture filtrate, where G. candidum was suppressed by the culture filtrate of T viride and T. hamatum. Alsol ,the reduction in A. cirri growth was increased when the concentration of the culture filtrate of T hamatum, T viride, followed by 7’, legonarum and T harzianum was increased. The tested concentrations of the tested bioagents exhibited Slight effect in reducing the growth of B. theobromae. b. In vivo experiment: The effect of T harzianum and T. hamatum i olates and the commercial products of Plant-guard (T harzianum and Rhizo-N (B. subtilis) were studied against Navel orange it rots in vivo. The percentages of fruit-rot and fruit-rot severity were 115 SUMMARY significantly decreased in all treatments and the decrease was increasedby increasing the bioagent concentration.Plant-Guard at all the tested concentrations was the most effective in decreasing and suppressing incidence and severity of fruit-rots caused by G. candidum during 1999 season. The same effect was obtained with spore suspension of T. hamatum, which gave the highest effect in reducing decay caused by A. citri. Also, T harzianum spore suspension followed by Rhizo-N and Plant-Guard were more effective in controlling incidence and severity of fruit-rots caused by B. theobromae. Data of 2000 season exhibited, also, significant reduction in both incidence and severity of fruit-rots caused by the tested fungi. The three bioagent concentrations entirely suppressed the decay caused by G. candidum, with exception of Plant-Guard at 1.5 ml/L, which decreased the infection to a low degree. Rhizo- N, followed by Plant-Guard, T. hamatum and T. harzianum greatly reduced the infection with A, Mil, At the same time, the higher concentration of the tested bioagents exhibited clear reduction to Navel orange fruit-rots. 4. The effect of the different concentrations of the tested bioagents on the quality of Navel orange during 1999 and 2000 seasons showed that there was an increase in the firmness of the treated fruits with the different concentrations of the tested bioagents. Also, the same direction was observed in case of total soluble solids and ascorbic acid in inoculated fruits and treated with the three tested concentrations of the tested bioagents. While Titratable acidity exhibited the converse effect, which inoculated fruits 116 SUMMARY with G. candidum, A. cirri and B. theobromae gave higher level of acidity. 5. Exposing Navel orange fruits to UV light greatly reduced rot development compared with unirradiated fruits. The efficacy ofUV was increased by increasing UV wive length and exposure time. Ultraviolet light at 365 run gave highest effect than irradiation with 254 nm at all exposure times. In all cases, the infection with the three tested fungi was suppressed and/or decreased to different degrees compared with check during seasons of 1999 and 2000. 6. The effect ofUV light on Navel orange quality during 1999 season showed that fruit firmness was increased with increasing UV wave length and exposure time. At the same time, the irradiated fruits gave high amounts ftotal soluble solids and ascorbic acid compared with check. ’Meantime, the lowest wave length ofUV increased TSS and ascorbic acid, while UV at 365 run gave the lowest levels. On the contrary, UV light minimized the Titratable acidity in the infected fruits with the tested fungi compared with check. During 2000 season the same effect was observed. However, UV at 365 nm gave the highest ’evels of fruit firmness. While, in case of total soluble solids and ascorbic acid, irradiated fruits with 254 nm for 1, 3 and 5 minutes exhibited the highest amounts than those exposed to UV at 365 nm. On the converse, exposing inoculated fruits with the tested fungi to UV at 254 nm gave higher levels of titratable acidity more than that exposed to UV at 365 nm, except 117 SUMMARY inoculated fruits with A. citri and irradiated with 365 nm for 3 minutes, which showed the highest level of acidity. 7. Dipping Navel orange fruits in the preparations ofSOPP, Kaligreen, ascorbic acid, salicylic acid and sorbic acid at 500, 1000 and 1500ppm before storage indicated that the reduction in both fruit-rots infection and fruit-rots severity caused by the tested fungi was increased compared with check. During 1999 season, sorbic acid at 1000 and 1500ppm was the most effective in decreasing both incidence and severity of fruit-rots caused by G. candidum. On the other hand, SOPP at l500ppm entirely inhibited the decay caused by A. citri, while salicylic acid at 1000 and 1500ppm exhibited higher effect in controlling the decay. Moreover, all the tested chemical salts demonstrated slight effect in reducing the decay caused by B. theobromae. During 2000 season, Kaligreen, ascorbic acid and sorbic acid each at l500ppm gave the best results in controlling G. candidum and A. citri. While, incidence and severity of infection caused by B. theobromae was completely suppressed by dipping the fruits in SOPP at 1500ppm and decreased to a large degree by dipping the fruits in salicylic acid, ascorbic acid and Kaligreen at l500ppm. 8. Treating Navel orange fruits with different concentrations of chemical salts after inoculation with the tested fungi exhibited obvious increase in fruit firmness, total soluble solids and ascorbic acid contents compared with untreated fruits. Meantime, these contents were greatly increased in inoculated fruits with the tested fungi and treated with SOPP 118 SUMMARY and sorbic acid at 1500ppm. The amount of acidity was decreased in the infected fruits treated with the different concentrations of the tested chemical salts, and increased in uninoculated and untreated ones. The same trend was obtained during 2000 season, wherever, firmness, total soluble solids and ascorbic acid were increased in the inoculated fruits and treated with different concentrations of chemical slats, while Titratable acidity was decreased. 9. In vivo experiment, screening of six fungicides against the three pathogenic fungi revealed that Eupare i was the most effective fungicide on the growth of G. candidum, followed by Bellkute, Tecto 45% and 2,4-D 35%, while Tecto 98% and 2,4-D 40% were the least effective fungicides. Also, Euparen and Bellkute were the most effective on A. citri, followed by Tecto 45%, while Tecto 98% and 2,4-D were the least effective in this respect. Tecto 45% was very effective fungicide in reducing the mycelial growth of B. theobromae, followed by Euparen, Tecto 98% and 2,4-D 35%, while Bellkute gave the same effect at 600 ppm. 2,4-D 40% was the least effective fungicide against the mycelial growth of B. theobromae. 10.Euparen fungicide at 1000 and 1500 ppm was the most effective fungicides, for controlling postharvest Navel orange fruit-rots, which entirely inhibited the infection with G. candidum and B. theobromae and also decreased incidence and severity of fruit-rots caused by A. citri. Also, Bellkute 119 SUMMARY fungicide at the highest concentration was effective in decreasing the infection with the tested fungi. During 2000 season, incidence and severity of fruit-rots were decreased with increasing the fungicide concentration. All the tested fungicides significantly reduced the decay incidence. Tecto 98% and 2,4-D 35% each at 1000 and 1500 ppm completely suppressed the infection with G. candidum. Euparen fungicide at 1500ppm entirely inhibited G. candidum infection and was very effective against A. cirri and B. theobromae. Belikute at 1000 and 1500 ppm caused great effect against disease incidence and severity of fruitrots caused by the three tested fungi. Tecto 98% gave moderate effect in controlling A. citri and B. theobromae, while 2,4-D 40% and Tecto 45% gave the least effect in controlling the decay disease. 11. Treated and untreated Navel orange fruits with the tested fungicides indicated that inoculated fruits with G. candidum and treated with Euparen were firmer than that treated with the other fungicides and untreated ones. Inoculated fruits with A. cirri and treated with 2,4-D 35% were firmer compared with control treatment. The same effect was observed in inoculated fruits and treated with the different concentrations of Tecto 45%. The different concentrations of Euparen, followed by Tecto 98% at 1500 ppm resulted in an obvious increase in total soluble solids of the inoculated fruits with the tested fungi compared with control treatment. 120 SUMMARY 121 SUMMARY Concerning ascorbic acid, data revealed that ascorbic acid content was comparatively higher in the inoculated fruits and treated with the different concentrations of Bellkute. In addition, inoculated fruits and treated with different fungicides showed high values of titratable acidity, while inoculated and untreated fruits gave the highest levels of acidity. The same trend was obtained during 2000 season. In this respect, fungicide treatments exhibited the highest levels of firmness. Total soluble solids and ascorbic acid showedalso higher amount in the inoculated and fungicide treated fruits. Meantime, Euparen at 1000 and l500pprti was the best fungicide, which gave higher amounts. On the contrary, acidity was decreased in the inoculated fruits and treated with the tested fungicides compared with control treatment. 12. Dipping inoculated Navel orange fruits with the tested fungi in two growth regulators, i.e. gibberellic acid, and ethrel, respectively caused significant reduction in both incidence and severity of fruit-rots compared with control treatments. In addition, increasing the concentration of both materials caused also gradual decrease in both incidence and severity of the disease. Moreover, no great variation Was detected in the effectiveness of both growth regulatory on the tested fungi. However, both A. cirri and B. theobromac were more affected than G. candidum. All the tested growth regulators caused different degrees of increase in the firmness, T.S.S. and Ascorbic acid compared with control treatment. On the contrary, acidity of the treated fruits was lower than that estimated in untreated fruits. 13. Treating Navel orange fruits with sodium meta bisulfit (Na2S205), sodium carbonate (NaC03) and hydrogen peroxide (H202) after inoculation with any of G. candidum, A. dirt and B. theobromae caused significant reduction in both incidence and severity of fruit-rots compared with untreated fruits. In addition, increasing the concentration of these materials resulted in gradual decrease in the disease. No significant differences were detected in the values of incidence and severity of fruit-rots due to the infection with the three tested fungi. Low decrease in fruit firmness at 20 and 30 gIL of all the tested chemicals, i.e. Na2S205, NaC03 and H202 compared with control treatment. Meanwhile, at 40 giL low increase was recorded. T.S.S. showed low decrease when the fruits treated with SO 2 at 20 giL and NaC03 and H202 at 20 and 30 giL compared with control treatment. The estimated Ascorbic acid recorded considerable increase compared with control treatment. Opposite results were obtained in case of fruit acidity. 14. Data of suspend any of Tecto 45% and Bellkute in water of different degrees of temperatures, i.e. 20, 40 and 50 0C revealed that both fungicides were more effective in reducing incidence and severity of fruit-rots at 40 then 500 C than at 200e compared with control treatment. In addition, increasing the concentration of both fungicides caused gradual decrease in the disease. 122 SUMMARY The inoculated fungi recorded low differences in their affect by the tested two fungicides, especially at 40 and 50°C than at 20°C. Great fluctuation in the firmness, T.S.S., Ascorbic acid and fruit acidity was detected due to variation in the used degrees of temperature and the fungicides. In this respect, firmness and T.S.S. were increased in the inoculated fruit and treated with the two fungicides (especially at 750 and 1250 ppm) at all the tested degrees of temperature. In the contrary, fruit acidity of the treated fruits was slightly decreased at all the tested degrees of temperature compared with control treatment. On the other hand, both fungicides caused considerable increase in Ascorbic acid at all the tested fungicide concentrations and degrees of temperature compared with untreated ones. 15. All the extracted mycotoxins by any of chloroform and ethyl acetate as well as crude of the culture filtrate of the tested fungi caused significant increase in percentages of both necrotic fruits and necrotic areas compared with control treatment. However, crude of the culture filtrate of 5 isolates belonging to A. citri (isolates 1, 3, 4, 5 and 6) and one isolate (No.1) belonging to B. theobromae failed to cause apparent symptoms of necrosis in the injected fruits in blossom-end. The same was observed when the mycotoxin of isolate No. 3 of A. cirri extracted with chloroform was injected in the blossom-end of the fruits. On the other hand, the percentages of necrotic fruits reach 100% when all types of mycotoxins of G. candidum 123 SUMMARY were injected in the blossom-end of the fruits. This percentage was also observed when mycotoxin of some A. citri isolates as well as the two isolates of B. theobromae were used. Fruits injected in the stem-end showed also different percentages of necrotic fruits. However, injection through stemend was of high deleterious effect than when injection occurred through blossom-end. The averages percentages of necrotic areas of the injected fruits with the extracted mycotoxins as well as due to the use of crude of the culture filtrate of the tested fungi were in the same trend with the percentages of necrotic fruits. 124 SUMMARY |