Curriculum Vitae Name : Samia Abdo Ahmed El-Fahar General specialization




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Curriculum Vitae



Name : Samia Abdo Ahmed El-Fahar

General specialization: Sugar crops disease.

Accurate specialization: Sugar beet disease.
Means of communications:

Tel. 047/3227164

(Mob.): 0106774323

e-mail: a_e_draz@yahoo.com.

Title of M.Sc. Thesis.

Studies on foliage diseases of sugar beet in Egypt.



Title of Ph.D. Thesis:

Integrated management of Cercospora leaf spot disease of sugar beet in Delta area.



STUDIES ON FOLIAGE DISEASES OF SUGAR BEET IN EGYPT

SUMMARY

Sugar beet (Beta vulgaris L.) is one of the most important sugar crops in many counties all over the world. In Egypt, sugar beet crop considers the second sugar crop after sugarcane, for sugar production. Cultivated area of sugar beet increased markedly during the last tow decades. The national acreage of sugar beet reached 42108 thousand feddan in 19984 and increased up to 50 thousand feddan in 1996.

Sugar beet is liable to be attacked by several diseases. These diseases cause severe losses in root yield and sucrose percentage. Many foliage fungal diseases infected sugar beet leaves, i.e., Cercospora leaf spot, alternaria leaf spot, downy mildew, powdery mildew and rust.

This work was carried out during 1993/94, 1994/5 and 1995/96 seasons at Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt.

The objectives of this study are to survey of the common foliage diseases and to give more emphasize on the most destructive leaf spot disease which caused by Cercospora beticoal from physiological point of view and pathogenicity tests. In addition studying the effect of inoculation time on the behaviour of some sugar beet cultivars and its effect on root yield and related quality characters.

Furthermore, study the effect of date of sowing on sugar bet characters under field conditions of Cercospora leaf spot. The following is a summary of the main results.

Survey and distribution of the fungal diseases infecting sugar bet leaves in Kafr El-Sheikh Governorate was done. survey of Cercospora leaf spot disease indicated that disease severity percentage for cv. Ras Poly ranged from 31 to 39%, which considered the highest disease severity among the sugar beet cultivars grown in this area.

In addition, survey and distribution of alternaria leaf spot showed that the disease severity was not severe in all districts. All varieties were infected by this disease but in low severity. The average of disease severity was 9% on cv. Ras Poly followed by cv. Pleno (8.7%).

Powdery mildew disease appeared at the end of the season. Ras Poly cultivar recorded a disease severity of powdery mildew ranged from 1.5 to 5%. In addition, Pleno cultivar scored a disease severity ranged from 3 to 10% in Al-Hamool and Kafr El-Sheikh district.

Rust disease appeared at the end of the season but in low incidence. Disease severity of rust for Top cultivar was 4% in Kafr El-Sheikh district.

Many diseases infected the leaves of sugar beet cultivars in Egypt. Isolation, identification of those diseases were done under Egyptian conditions for sugar beet areas. Those diseases are; Cercospora leaf spot, alternaria leaf spot, powdery mildew, rust and nigrospora leaf spot.

Relative frequency of Cercospora and alternaria spots on sugar beet leaves were estimated and isolated on PDA medium. The highest frequency was recorded for Cercospora leaf spot cvs. Ras Poly (80%), Pleno (75.5%) and Top (72.5%) than alternaria spots. While, Kawamira and Top have relatively more spots of alternaria; 30 and 27.5%, respectively, but in general less spots were observed than Cercospora leaf spots.

Six isolates of Cercospora beticola from different locations were tested for their pathogencity to sugar beet cv. Ras Poly . Data indicated that disease severity was 4.80 and 30.07% for isolate No. V and isolate No. 1, respectively. Retest the virulent isolate No. 1 on 7 sugar bet cultivars revealed that, Ras Poly and Top cultivars scored the highest disease severity (28 and 19%, respectively).

The biggest lesion area of Cercospora leaf spot disease was obtained for Ras Poly (2.38 mm2) and Kawmira (1.95 mm2) sugar beet cultivars.

Physiological tests have been studied for Cercospora beticola. Data obtained revealed that the highest linear and rate of growth was obtained from sugar beet leaf extract dextrose agar (SBLEDA), Czapek's and Balis and Pane media. Data also revealed that the highest dry weight (mg) was obtained from boiled pea leaf extract, yeast extract (BPLEYE) and Czapek's media, on the other hand, the least dry weight was obtained from chopped carrot leaves (CCL) medium.

Media of Czape's, BPLEYE and Balis and Payne, gave the highest sporulation rate of 359.50, 179.68 and 171.93 x 103 spores/ml respectively. On the other hand, no spores were produced from PDA and chopped sugar beet leaf (CSBLA) media.

The maximum of linear growth, rate of growth, dry weight and spore production rate of Cercospora beticola was produced under 25 and 30oC. ON the other hand, low records were obtained for linear growth, rate of growth, dry weight and no. of conidial spores on, 15 and 35iC. While on 10o temperature there is no sporulation produced.

The highest amount of linear growth, rate of growth and spore production rate of Cercospora beticola was obtained between pH 5 and 6. While the lowest values were obtained for linear, rate of growth and sporulation rate under pH levels 7 up to 10. In addition, pH 3 was not suitable either for growth or sporulation of the fungus.

Screen house experiments under artificial inoculation during 1995/96 showed that there were significant differences among the sugar beet cultivars that was inoculated at different ages (90, 105 and 120 days for sowing). The severity of infection on plants of the same sowing date and inoculated at 120 days after sowing was higher than that inoculated at 90 or 105 days after sowing. The severity of infection was 38.97, 39.72 and 50.0% for 90, 105 and 120 days from sowing, respectively on cv Ras Poly. Whereas, it was 28.59, 32.78 and 34.00% for 90, 105 and 120 days from sowing respectively on cv. Top.

The data obtained reported that there were significant differences among the four disease severity scores severely 15 days intervals, for the three times of artificial inoculation; 90, 105 and 10 days after sowing for all cultivars tested.

The results indicate that, the third time of artificial inoculation (120 days) scored the highest disease severity in comparison with the first and second time of inoculation for all scores and cultivars.

Area under disease progress curve (AUDPC) values were higher in the third time of inoculation (120 days after sowing) than the first time of artificial inoculation (90 days after sowing) for all the tested cultivars. The values of AUDPC were related to disease severity. AUDPC values were which ranged from 1190 for cv. Ras Poly to 628.35 for cv. Kawarmira.

Rate of disease increase (r-value) ranged from 0.071 in the first time of inoculation to 0.135 in the third time of inoculation for Ras Poly. On the other hand, Kawarmira cultivar scored the lowest r-value for the three times of inoculation.

Estimating of yield components and losses revealed that artificial inoculation of sugar beet plants with C. beticola resulted in remarkable reduction of root weight comparing to healthy plants.

Significant differences were obtained between the two inoculation times (90 and 105 days from sowing) and the third inoculation time for Top, Kawamira and Pleno cultivars.

Losses percentage in root yield per plant ranged from 49.19 in the third time of artificial inoculation, 120 days after sowing to 61.30 in the first time of inoculation, 90 days after sowing for Ras Poly cultivar. High reduction in yield for Kawamira cultivar in the first and second time of inoculation; 90 and 105 days after sowing (61.20 and 62.72%, respectively).

In general, high yield losses were obtained for the first time of inoculation (90 days after sowing) than the third time of inoculation (120 days after sowing) for all the tested cultivars.

Significant differences in percentage of TSS were obtained between the first inoculation time (90 days after sowing) and both the second and third inoculation time for all cultivars tested. TSS values were lower for the first time of inoculation (90 days) in comparison with the other two inoculation times; 105 and 120 for cv. Ras Poly. Artificial inoculation at 90 days old plants resulted in less sucrose percentages in all tested cultivars which recorded; 9.72, 9.48, 10.3 and 10.73% for Ras Poly, Top, Kawmira and Pleno, respectively. In addition, both Kawamira and Pleno cvs. Recorded high percentages of sucrose.

Losses in sucrose percentages were 43.48, 45.29, 44.92 and 40.97 in the first time of inoculation (90 days from sowing) for cvs. Ras Poly, Top, Kawamira and Pleno,, respectively. On the other hand, loses percentage in the th ird time of inoculation (120 days from sowing) were 31.68, 34.14, 26.07 and 24.22 for cvs. Ras Poly Top, Kawamira, and Pleno, respectively. In general, the highest loss percentages in sucrose were found n the first time of inoculation (90 days after sowing).

Percentage of sugar beet juice purity was greatly decreased due to infection with C. beticola. There were significant differences between the three, inoculation times; 90, 105 and 120 days after sowing for cvs. Ras Poly, top, Kawamira and Pleno. The least purity percentage value was obtained from Top followed by Ras Poly cultivar.

There are significant differences among disease severity levels in chlorophyll content. Significant differences among time of inoculations; 90, 105 and 120 days, and also among cultivars. Chlorophyll content decreased more by delaying the date of infection. Also, the decrease in chlorophyll content was clear in the cvs. Top and Kawamira.

Natural infection under three dates of sowing, Sept. 25, Oct. 25 and Nov. 25. The data showed that disease severity higher in the third date of sowing than the second and first date of sowing, during 1994/95 and 1995/96 seasons for all the varieties tested. Moreover, Ras Poly cultivar showed high disease severity in the three dates of sowing and in the two seasons than the other cultivars. Disease severity percentages in general were higher in the second season than in the first season.

AUDPC values revealed to disease severity in the two seasons showed significant differences for both dates of sowing and cultivars AUDPC values were higher in the third date of sowing than the second and first date of sowing in the two seasons of 1994/95 and 1995/96. Moreover, AUDPC values for Ras Poly was high followed by Pleno. Low values of AUDPC in the first season of 1994/95 than the second season of 1995/93.

Rate of disease increase (r-value) during 1994/95 was higher in the third date of sowing (Nov. 25). Moreover, there were significant differences among all the these dates of sowing. Ras Poly cultivar scored the highest among all the cultivar tested. Similar results were obtained during 1995/96 season. Pleno cultivar differed significantly than the other cultivars for rate of disease increase (r –value).

High percentages of sucrose purity and TSS were obtained for 1994/95 than 1995/96 season. Sucrose percentage was high in the first date of sowing and low in both second and third date of sowing. For all the tested cultivars in the two seasons.

Losses in root weight/feddan were related to AUDPC values. Significant differences were obtained among the dates of sowing for the tested cultivars in the two seasons. High losses of root weight/feddan were obtained for the third date of sowing in the two seasons also.

Losses in sucrose percentage were low in the first season of 1994/95 than in the second season 1995/96. Significant differences were obtained for sucrose losses either among dates of sowing and or cultivars.

Integrated management of Cercospora leaf spot disease of sugar beet in Delta area

SUMMARY

Cercospora leaf spot disease caused by Cercospora beticola is the most destructive foliage diseases of sugar beet in Nile delta Governorates of Egypt namely, Kafr El-Sheikh. Dakahlia, Gharbia, Menofiya and Damietta. This study was conducted to study the integrated management of the disease in such area. Results obtained throughout this investigation can be summarized as follows:

1. Survey study of Cercospora leaf spot disease conduced in the five different Governorates of Nile delta revealed the widespread of the disease in all Governorates. Kafr El-Sheikh ranked the first in this respect since it is considered the first Governorate in cultivating sugar beet in Egypt.

2. Pathogenicity of seven isolates of C. beticola isolated from diseases sugar beet leaves varied in their virulence. The most virulent isolate was IV followed by II.

3. Evaluation of ten sugar beet cultivars toward infection with C. beticola indicted that all cultivars differed in their susceptibility. Ras Poly cv. was the most susceptibility. Ras Poly cv. was the most susceptible (disease severity of 35.70%). While Fared acv. was the least (19.84%). In addition a remarkable reduction in chlorophyll content, root weight/plant and sucrose percent was observed. The highest loss percent age of both root weight/plant and sucrose was noticed in Ras Poly cv., while lowest percent was detected in Fareda cv.

4. A comparison study of healthy and infected leaves with C. beticola of the two sugar beet cultivars; Ras poly and Fareda in relation to stomatal apertures showed that length and width of stomata at healthy leaves of RAs Poly cv. were longer and wider than of Fareda cv. Moreover, the number of stomata/mm2 of the outer leaves of both cultivars was higher than that in the inner heart ones. Therefore, adult outer leaves always infected while the heart young leaves were resistant. On the other hand, results of the same study carried out in relation to phenolic contents revealed that free, conjugated and total phenolic compounds were increased in leaves of both cultivars after inoculation with C. beticola and their content was higher in young leaves than in mature ones.

5. Through element analysis of leaves, the present results showed that nitrogen, phosphorus, iron, manganese and copper contents increased in adult leaves more than in young ones. In the other hand, potassium and zinc were higher in young leaves than in adult ones for both Ras Poly and Fareda cvs. However, the latter two elements were higher in Fareda than in RAs Poly cvs.

6. There was remarkable antagonistic effect of both the bacterial isolates of P. flourescece and B. subtilis was well the fungus T. harzianum against C. beticoal in vitro under different temperature degrees. On the other hand, in greenhouse experiment, both bacterial bioagents were more effective in reducing the disease severity in comparison to T. harzianum which showed slight effect on reducing disease severity. Cultural filtrates of both bacterial bioagents were less effective in reducing disease severity. Moreover, application of each bacterial bioagents by spraying once before inoculating plants with the pathogen and two sprays after with 3-days intervals were more effective in reducing disease severity. The use of the fungicide Topsin M 70 in combination with both bacterial bioagents significantly reduced disease severity compared by application of each alone In addition the quantity of the fungicide was decreased to ¼ or ½ the recommended dose, consequently reduced costs and pollution.

7. An attempt to use plant extracts in controlling Cercospora leaf spot disease in vitro revealed that extracts of five different plants i.e. Pancreatum maritinum, Solanum nigraum, Schinus terebenthifoious, Ammi visnaga and Anthemis nobilis, suppressed growth of the causal fungus C. beticola. The effect of those extracts was obviously increased by increasing their concentrations. On the other hand, in greenhouse, application of such extracts by spraying once before inoculating plants with the pathogen suspension and twice after with 3-days intervals, significantly reduced disease severity (%) at all three different concentrations used. However, such application of either Ammi visnaga or Anthemis nobilis at 4000 ppm was more effective than all alternative applications used. In addition, under field conditions, twice sprays just after disease appearance gave good results in reducing disease severity (%). consequently, such effect was reflected on increasing sucrose and TSS percentages.

8. Fertilizers played an important role in reducing disease severity of Cercospora leaf spot resulting in increasing root sucrose yield. Application of nitrogen (90 kg N/feddan), potassium (48 kg K2O/feddan) and zinc (5 kg/feddan) reduced in general disease severity percentage of all tested cultivars. In addition, application of the recommended dose of nitrogen, potassium and zinc increased both TSS% and sucrose yield.

9. Test of five different commercial fungicides Cobox, Tecto. Sumi-eight, Thiovit 80 and Topsin M 70 revealed that Topsin and sumi-eight were the most effective ones in controlling Cercospora leaf spot disease.

10. Study the disease severity of Cercospora leaf spot in relation to number of spore of C. beticola and certain meteorological elements at four different locations at Kafr El-Sheikh Governorate indicated that disease severity varied from one location to another depending on sowing date, meteorological elements and number of spores. Disease severity (%) correlated significantly with maximum, minimum air temperature, maximum, minimum relative humidity, rain amount, wind velocity and number of spores in atmosphere. The highest disease severity was obtained when maximum relative humidity was more than 85% and the minimum relative humidity was more than 85% and the minimum was < 40-53%. On the other hand, number of spores was positively correlated with meteorological elements. It was affected by air temperature ranged between < 7-30oC and increased b increasing wind velocity.

11. Using different regression equations as models for predicting disease severity (%) of Cercospora leaf spot in relation to all weather conditions resulted in proposing general model for Kafr El-Sheikh governorate which led to scout and forecast the disease severity, number of spores and its reliability n meteorological data. In addition, determination coefficients of such models showed high level of acceptability the multifcactor model and how it became reliable for such area of sugar beet plantations.

El-Kazzaz, M.K.; M.A. El-Sharkawy; M.M. El-Naggar and El-Fahar, Samia A. (2003). Certain pathological, histological and biochemical studies on Cercospora leaf spot disease of sugar beet. Tenth Congress of Phytopathology, Giza, Egypt.

ABSTRACT

Pathogenicity of seven isolates of Cercospora beticola isolated from diseased sugar bet plants cultivated in different governorates of Nile Delta varied in their virulence.

Evaluation of ten sugar beet cultivars toward infection with C. beticola indicated that all tested cultivars were susceptible at different degrees. Cultivar as Poly was the most susceptible while cv. Fareda was the least. In addition, a remarkable reduction in chlorophyll content, root weight/plant and sucrose percent observed. The highest loss percentage of both root weight/plant and sucrose was noticed in cv. Ras Poly, while the lowest percent was detected in cv. Fareda.

A comparison study of health and infected leaves with C. beticola of the two sugar beet cultivars; Ras Poly and Fareda in relation to stomatal apertures showed that length and width of stomata at healthy leaves of cv. Ras Poly were longer and wider than of cv. Fareda. Moreover, the number of stomata/mm2 of the outer leaves of both cultivars was higher than that in the inner heart ones. Therefore, adult outer leaves were susceptible while the heart young leaves were resistant. On he other hand, results of the same study carried out in relation to phenolic contents revealed that free, conjugated and total phenolic compounds increased in leaves of both cultivars after inoculation with C. beticola and their content was higher in young leaves than in mature ones.

Through element analysis of leaves, the present results showed that nitrogen, phosphorus, iron, manganese and copper contents increased in adult leaves more than in young ones, on the other hand, potassium and Zinc were higher in young leaves than in adult ones for both cvs. Ras Poly and Fareda. However, the latter tow elements were higher in cv. Fareda, the resistant than in cv. Raspoly the susceptible one.

El-Kazzaz, M.K.; M.A. El-Kholy; M.M. El-Naggar and El-Fahar, Samia A. (2003). Alternative control measures of Cercospora leaf spot disease of sugar beet by certain bioagents and plant extracts. Tenth Congress of Phytopathology, Giza, Egypt.

ABSTRACT

Use of certain antagonistic bioagents in controlling Cercospora leaf spot disease of sugar beet was studied in vitro and in greenhouse. There was remarkable antagonistic effect of both the bacterial isolates of Pseudomonas flourescense and Bacillus subtilis was well as the fungus Trichoderma harzianum against Cercospora beticola in vitro under different temperature degrees. On the other hand, in greenhouse experiments both bacterial bioagents were more effective in reducing the disease severity in comparison with T. harzianum that showed slight effect on reducing disease severity. Cultural filtrates of both bacterial bioagents were less effective in reducing disease severity. Moreover, spraying bacterial bioagents once before inoculating plants with the pathogen and twice after 3-days intervals were more effective in reducing disease severity. The use of fungicide Topsin M70 in combination with both bacterial bioagents significantly reduced disease severity compared to application of each alone. In addition, reducing the quantity of the fungicide was used to ¼ or ½ of the recommended dose, consequently reduced costs and pollution.

In an attempt to use plant extracts in controlling Cercospora leaf spot disease of sugar beet in vitro and under greenhouse conditions, it was revealed that the extracts of five different plants, i.e. Pancreatum maritinum, Solarnum nigrum, Schinus terebenthifolious, Ammi visnaga and Anthemis nobilis, suppressed growth of the causal fungus C. beticola in vitro. The effect of these extracts was obviously increased by increasing their concentrations. On the other hand, in greenhouse, application of such extracts by spraying once before inoculating plants with the pathogen suspension and twice after with 3-days intervals, significantly reduced disease severity (%) at the three different concentrations used. However, such application of either Ammi visnaga or Anthemis nobilis at 40000 ppm was more effective than all alternative application used. Consequently, such effect was reflected on increasing sucrose and TSS percentages.

El-Kazzaz, M.K.; M.A. El-Sharkawy; M.M. El-Naggar and El-Fahar, Samia A. (2003). Eidemics of Cercospora leaf spot disease of sugar beet in north delta of Egypt. Tenth Congress of Phytopathology, Giza, Egypt.

ABSTRACT

The epidemic of Cercospora leaf spot was studied in four different localities in North Delta of Egypt (Kafr El-sheikh Governorate). Studying the disease severity of Cercospora leaf spot in relation to the number of spores of C. beticola and certain meteorological elements at four different locations at Kafr El-Sheikh Governorate indicated that disease severity varied from one location to another depending on sowing date, meteorological elements and number of spores. Disease severity (%) correlated significantly with maximum and minimum air temperatures, maximum and minimum relative humidity, rain amount, wind velocity and number of spores in the air. The highest disease severity was obtained when maximum and minimum relative humidity exceeded 85%. On the other hand, number of spores was positively correlated with meteorological elements. It was affected by air temperature ranging between 7-30%oC and increased by increasing wind velocity.



Using different regression equations as models for predicting disease severity (%) of sugar beet Cercospora leaf spot in relation to all weather conditions resulted in proposing models for Kafr El-Sheikh Governorate which led to scout and forecast the disease severity, number of spores and its reliability on meteorological data. In addition, determination coefficient of such models showed high level of acceptability the multi factorial model and how it become reliable for such area of sugar beet plantations.


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