Scholarly article on topic 'Fungicidal management of chocolate spot of faba bean and assessment of yield losses due to the disease'

Fungicidal management of chocolate spot of faba bean and assessment of yield losses due to the disease Academic research paper on "Agriculture, forestry, and fisheries"

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{"Faba bean" / "Chocolate spot" / " Botrytis fabae " / "Disease severity"}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — El-Sayed, A. Sahar, Rania Z. El-Shennawy, A.I. Ismail

Abstract This work was carried out at Sers El-Lyain Agriculture Research Station Farm, El-Minufiya Governorate during 2007/08 and 2008/09 growing seasons to evaluate the amount of losses in the seed yield of the five faba bean cultivars Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2 under. In vitro studies show that Dithan M45 was the most effective agent against Botrytis fabae than Galben manozeb and copper oxychloride. Application Dithan M45 of under greenhouse conditions, 2 days before inoculation reduced the disease severity (3.11%) at 200ppm compared with the control treatment (18.59%) on Giza 40 cv., while the symptoms did not appear at the same concentration on other tested cultivars. It was observed that, the cvs. Giza 716 and Sakha 2 showed lower infection than the other tested cvs, except with Giza 40 which was highly susceptible. Field studies showed significant differences under the influence of chocolate spot disease. The area under the disease progress curve (AUDPC) was higher on Giza 40 followed by Sakha 1, Giza 3 Mohassen, Sakha 2 and Giza 716, respectively, with higher disease infection in the first season 2007/08 than 2008/09 season. High negative significant correlation (r) was obtained between AUDPC and the yield of the five tested cultivars in the two seasons. High negative correlation was observed between disease severity and each of plant height, number of branches, number of pods, weight of pods and weight of 100 seeds of Giza 40 and Sakha 1 in the first season. High negative regression coefficient (b) was found between each of the five studied characters and disease severity of five cultivars. However, plant height and number of branches were not significant for the Giza 716 and Sakha 2. The regression coefficient (b) values were found significant for number of pods (X 3) with 0.532 and 0.096, for weight of pods (X 4) with 0.422 and 0.0126 and for weight of 100 seed (X 5) with 0.753 and 0093 for Giza 716 in the two seasons, respectively. While for Giza 40 these values were 0.644 and 0.226, 0.115 and 0.64 and 0.159 and 0.222, respectively. Coefficient of determination (R 2) values were 0.63 and 0.341 for Giza 716 and were 0.757 and 0.854 for Giza 40 for the weight of pods in the two seasons, respectively.

Academic research paper on topic "Fungicidal management of chocolate spot of faba bean and assessment of yield losses due to the disease"

Annals of Agricultural Science (2011) 56, 27-35

Faculty of Agriculture, Ain Shams University Annals of Agricultural Science

www.elsevier.com/locate/aoas

ORIGINAL ARTICLE

Fungicidal management of chocolate spot of faba bean and assessment of yield losses due to the disease

El-Sayed, A. Sahar *, Rania Z. El-Shennawy, A.I. Ismail

Plant Pathology Research Institute, Agricultural Research Center, Giza, Egypt

Received 11 January 2011; accepted 20 April 2011 Available online 11 August 2011

KEYWORDS

Faba bean; Chocolate spot;

Botrytis fabae; Disease severity

Abstract This work was carried out at Sers El-Lyain Agriculture Research Station Farm, El-Min-ufiya Governorate during 2007/08 and 2008/09 growing seasons to evaluate the amount of losses in the seed yield of the five faba bean cultivars Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2 under. In vitro studies show that Dithan M45 was the most effective agent against Botrytis fabae than Galben manozeb and copper oxychloride. Application Dithan M45 of under greenhouse conditions, 2 days before inoculation reduced the disease severity (3.11%) at 200 ppm compared with the control treatment (18.59%) on Giza 40 cv., while the symptoms did not appear at the same concentration on other tested cultivars. It was observed that, the cvs. Giza 716 and Sakha 2 showed lower infection than the other tested cvs, except with Giza 40 which was highly susceptible. Field studies showed significant differences under the influence of chocolate spot disease. The area under the disease progress curve (AUDPC) was higher on Giza 40 followed by Sakha 1, Giza 3 Mohassen, Sakha 2 and Giza 716, respectively, with higher disease infection in the first season 2007/08 than 2008/09 season. High negative significant correlation (r) was obtained between AUDPC and the yield of the five tested cultivars in the two seasons. High negative correlation was observed between disease severity and each of plant height, number of branches, number of pods, weight of pods and weight of 100 seeds of Giza 40 and Sakha 1 in the first season. High negative regression coefficient (b) was found between each of the five studied characters and disease severity of five cultivars. However, plant height and number of branches were not significant for the Giza 716 and Sakha 2. The regression coefficient (b) values were found significant for number of pods (X3) with 0.532 and 0.096, for weight of pods (X4) with 0.422 and 0.0126 and for weight of 100 seed (X5) with 0.753 and 0093 for Giza 716 in the two seasons, respectively. While for Giza 40 these values were

Corresponding author. Tel.: +20 2 1296 4444. E-mail address: sahar_abbas2002@yahoo.com (A. Sahar).

0570-1783 © 2011 Faculty of Agriculture, Ain Shams University. Production and hosting by Elsevier B.V. All rights reserved.

Peer review under responsibility of Faculty of Agriculture, Ain Shams University.

doi:10.1016/j.aoas.2011.05.004

0.644 and 0.226, 0.115 and 0.64 and 0.159 and 0.222, respectively. Coefficient of determination (R2) values were 0.63 and 0.341 for Giza 716 and were 0.757 and 0.854 for Giza 40 for the weight of pods in the two seasons, respectively.

© 2011 Faculty of Agriculture, Ain Shams University. Production and hosting by Elsevier B.V. All rights

reserved.

In Egypt, chocolate spot and rust are considered as the major disease problems on broad bean resulting in economic losses and affect the longevity of broad bean cultivars (Hagg, 1956; Mohamed et al., 1981; Harrison, 1988; Koike, 1998; Morsy, 2000). During the last few years, chocolate spot started to develop on the new broad bean cultivars with varying degrees in infection under epiphytotoxic conditions (Dabour, 2001).

Chocolate spot caused by (Botrytis fabae) attacks all of the above ground parts of the broad bean plant and causes losses by reducing seed yield and affected seed quality due to the prevailing environmental conditions (Mohamed et al., 1981; Morsy, 1993). Johanson et al., (1994) stated that foliar disease of faba bean and chocolate spot reduced the yield. Ibrahim et al. (1979) reported that losses in faba bean yield caused by chocolate spot and rust diseases could reach up to 50% in the North of Delta. Mohamed (1982) in Egypt reported that natural infection of 10 fabae bean entries with leaf spot, rust and downy mildew caused yield losses that reached 22.8%.

Many methods of control are possible such as the use of resistant genotypes, chemicals (fungicides), and biological, induced resistant and modified cultural practices. In fact, the amount of losses in seed yield due to a disease determines the importance of that disease. A chemical is recommended for use when the cost of its application equals to or is less than the returns gained. This pot is called the damage threshold or the tolerant limit. The objectives of this study were to:

(1) Study of some fungicides on linear growth of the causal organism in vitro.

(2) Study the reaction of some cultivars to infection by the causal organism under greenhouse.

(3) Determination of loss in seed yield of the currently used cultivars using area under disease progress curve (AUDPC) in field experiments.

Evaluation of the obtained data following statistical analysis using correlation coefficient (r), regression coefficient (b) and coefficient determination (R2).

Materials and methods

Source of the pathogen

The pathogenic isolate of B. fabae used in the present investigation from leguminous and forage crop Disease Department, Plant Pathol. Res. Instit., A.R.C. This isolate proved to be aggressive in previous studies.

Laboratory experiments (in vitro assay)

Three fungicides namely, Dithane M45, Galben manozeb 584 and copper oxychloride were tested on linear growth of

B. fabae. Seven concentrations: 0, 10, 25, 50, 100, 200 and 250 ppm of active ingredient of fungicides were prepared according to the active ingredient. The medium was amended with each compound just before solidification. Ten milliliters of each PDA medium was poured in each Petri dish then they were inoculated with 5 mm discs of fungal growth and incubated at 20 0C. The fungal growth was measured when radial growth in any treatment reached its maximum. Fungitoxicity was expressed in terms of percentage of mycelia growth inhibition and calculated as formula (Pandey et al., 1982):

Percentage of mycelia growth inhibition = (dc-dt)/dc)x 100 where:

dc: Average diameter of fungal colony in the check. dt: Average diameter of fungal colony in treatments.

Effect of Dithane M45 of disease incidence

The reaction of five broad bean cultivars; Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2 to the infection with B. fabae was tested at 45 day old, under greenhouse conditions. Five seeds of each cultivar were sown in pots No. 25 and Dithane M45 was applied at the rate of 0, 25, 50, 100 and 200 ppm. Five plants 45 days old from each Cv. were sprayed with the fungicide. The application was carried out 2 days before inoculation. A spore suspension of the pathogen was prepared fresh immediately before application at 2.5 x 105 spores/ ml. Plants sprayed with tap water only served as the control. All plants were covered with poly ethylene bags for 24 h to maintain high relative humidity, then kept under greenhouse conditions.

Severity of infection as a mean of whole plant infection was estimated according to the method of Hanouike and Hasanain (1986) as follows:

Disease activity % = -- x 100

N = number of infected leaves, V = numerical grade, 9 = Higher degree in the category.

Field experiments

A split-plot design experiment was carried out at Sers El-Lyain, Minufiya Governorate during two successive seasons 2007/08 and 2008/09. This experiment includes:

(a) Natural infection, in which the plots were only sprayed with tap water.

(b) Natural infection but the plants were kept nearly chocolate spot free by spraying Dithane M45 that was used at 2.5 g/L three times, after 45, 60 and 90 days from sowing with 2 weeks interval up to the fifth application on April 1 of the two season.

The sub-treatments were allocated to the five cultivars i.e., Giza 3 Mohassen, Gia 716, Giza 40, Sakha 1 and Sakha 2. Each treatment was replicated three times in plots with 3 rows. The plot area was 10.5 m2 (3 m length and 3.5 m widely).

Seeds were sown as two seeds/hole in rows, at the two edges of each hill with 20 cm. Sowing dates were: November 30 for the two growing seasons. The first score was started at January 22 and every 2 weeks interval up to the 5th score for the two growing seasons.

At harvest, the seed yield was determined from the net harvested area (10.5 m2) of each plot, also, plant height (cm), No. of branch/plant, No. of pod/plant, weight of pod/plant and weight of 100 seeds were taken.

Loss of the growth characters

Percentage yield and another growth characters loss were calculated on the basis of disease-free nearly plots. The yield data for disease-free and diseased plots were compared statistically.

Infection development

Chocolate spot infection was observed during the last week of January, 2007/08 and 2008/09 for the two seasons, respectively. The mean plant infection was calculate as an average of the whole plant. First score was at January 22 and every 2 weeks up to the fifth score in the both season.

Area under disease progress curve (AUDPC) was calculated using the adapted formula by Pandey et al. (1989) as follows:

AUDPC = D

Yk - 1)

where: Y1, Y2 ... YK are the K disease scores at a constant interval of D days.

Statistical analysis was carried out according to Gomez and Gomez (1984), while regression analysis was estimated according to Draper and Smith (1981).

Results

Laboratory experiments

Data in Table 1 show the in vitro effect of the tested concentrations of Dithane M45, Galben manozeb and copper oxychlo-ride on the growth of B. fabae. It is clear that Dithane M45 and Galben manozeb were the most effective fungicides against B. fabae followed by copper oxychloride, respectively.

The differences between Dithane M45, Galben manozeb and copper oxychloride were significant. Data also indicate that the tested fungus varied in its sensitivity against the three fungicide used complete growth inhibition was recorded at 200 and 250 ppm of Dithane M45 followed by Galben manozeb recorded at 250 ppm, respectively while, no complete growth reduction for the fungus tested occurred when copper oxychlo-ride was used until 250 ppm.

Effect of Dithane M45 of disease incidence

Five broad bean cvs. were artificially inoculated with B. fabae the causal organisms of chocolate spot under greenhouse conditions. The Dithane M45 fungicide was spray 2 days before inoculation. Results in Fig. 1 indicate that the Dithane M45 reduced significantly chocolate spot infection than the untreated pots. Significant differences were also found between the five cvs. used, Giza 40 cv. showed higher infection than others. While, Giza 716 and Sakha 2 showed the least infection. Significant differences were also found either among concentrations. On the other hand, Giza 716 cv. and other cvs. except Giza 40 showed 100% reduction in symptoms of disease.

L.S.D. at5% for : Cultivar(A) = 0.88 Concentration(B) = 0.29Cultivar x Concentration(A x B) = 0.65

Results presented in Table 2 showed chocolate spot severity on faba bean. This severity was significantly increased from the 1st to the 5th record period in both seasons, also the differences between cultivars were significant.

Field experiments

Disease development increased on all cultivars to its higher level at the fifth score of March (24) 2008. At the fifth score March (24), 2008 severity of infection on the cvs. Giza 716 and Sakha 2 under naturally infected plots, were 3.550% and 3.850%, respectively. While, under protected plots, were 1.700% and 3.550%. on Giza 3 Mohassen and Sakha 1, severity of infection at the fifth score were 43.67% and 46.670%. Under naturally infected plots, were 39% and 35.33%, while under protected plots, were 2.000% and 1.443%, respectively (Table 2).

The higher susceptible cv. Giza 40, showed severity of infection was 8.860% and 3.850% on the plants of naturally and protected plots respectively. Lower disease severity of infection was observed on different cultivars at the first January 22 to

Table 1 Reduction% in growth of Botrytis fabae in response to different concentrations of Dithane M45, Galben manozeb 584 and copper oxychloride.

Tested fungicide or biocide Concentration (ppm)

0 10 25 50 100 200 250

Dithane M45 0.0 13.70 28.15 51.85 95.56 100 100

Galben manozeb 0.0 14.81 21.11 44.81 65.93 92.59 100

Copper oxychloride 0.0 11.11 18.52 33.33 48.15 77.78 83.70

L.S.D. at 5% for: interaction = 5.46.

□ Giza 3 Mohassen HI Giza 716 S Giza 40 S Sakha 1 B Sakha 2

25 50 100

Concentration (ppm)

Fig. 1 Mean chocolate spot severity (%) on five broad bean cultivars under the effect of Dithane M45 as spray on artificial inoculum at 45 days under greenhouse.

last score March (24) 2009 season than the first season 2007/ 2008. In second season, severity of infection on cvs.

Effect of different levels of causal organism infection on AUDPC, seed yield and losses percentage in 2007/08 and 2008/ 09 seasons

Results in Table 3 showed that AUDPC of the cvs. Giza 716 and Sakha 2 in season 2007/08 were (508.877 and 617.177) and (348.05 and 454.403) with corresponding yield of (2.86 and 3.03) and (2.52 and 3.93 kg/plot), respectively. Percentage loss in seed yield were (18.66 and 22.95) and (0.0% and 0.0%), respectively. While the AUDPC values, on cv. Giza 3 Mohassen were 677.35 and 492.95 with corresponding yield of 2.63 and 3.65 kg/plot in plots of four inoculum levels, respectively. The percentages loss in seed yield of the four inoculum levels were 27.79% and 0.0%, respectively. On cvs. Giza 40 and Sakha 1 AUDPC values were (836.75 and 715.75) and (621.027 and 507.15) while the yield values were (1.83 and 2.31) and (2.83 and 3.45 kg/plot), respectively. The corresponding yield loss% were (35.50 and 32.82) and (0.0% and 0.0%) under the four inoculum levels, respectively. In

general, similar results was obtained in the second season 2008/09 but the values of AUDPC for all cultivars was less than the first season 2007/08 and did not reach the aggressive stage. The highest values were recorded by Giza 40 (262.68 and 125.25) with corresponding yield of (2.54 and 3.21 kg/plot) and the percentage loss in seed yield was (20.32% and 0.0%) under the four inoculum levels, respectively. On another hand, the cv. Giza 716 exhibited the lowest values of AUDPC (120.78 and 20) with corresponding yield (3.46 and 4.28 kg/plot) and had the lowest values of yield loss% (12.53% and 0.0%), respectively.

Effect of chocolate spot disease on some plant characters

Results in Table 4, indicated that severity of infection%, plant height, number of branches, number of pods/plant, weight of pods/plant and weight of 100 seeds were significantly different between the cultivars except for number of branches in two seasons was not significant.

Results in Table 4 indicated that severity of infection ranged from (45.33% and 12.0%), (35.33% and 9.0%), (27.67% and 4.0%), (34.67% and 5.0%), (29.33% and 3.67%) and (25.33% and 3.0%) on the cvs., Giza 40, Sakha 1 and Giza 716 in the two seasons 2007/08 and 2008/09 under the four levels of infection, respectively.

Plant height was significantly affected by disease severity. Results in Table 4 showed that the plant height were 104.67, 119.00, 107.67, 99.67 and 102.67 cm for Giza 3, Giza 716, Giza 40, Sakha 1 and Sakha 2, respectively, under the protected plots in first season (2007/2008) while were 106.67, 118.67, 102.33, 97.33 and 108.00 cm for the same cultivars in the second season.

Number of branches per plant was not significantly affected as a results of interaction between the cultivar and disease in urea. Number of pods/plant was significantly affected with disease severity. The number of pods/plant was (12.67 and 22.00), (12.0 and 26.0), (16.33 and 23.33) and (15.33 and 28.33 pod/plant) for the cvs. Giza 716 and Sakha 2 in two seasons, respectively. Weight of pods/plant was increased (49.33 and 51.0 g/plant) of the two cvs. Giza 716 and Sakha 2

Table 2 Disease development as a severity of infection of chocolate spot on five faba bean cultivars in two seasons (2007/08 and 2008/ 09), under field conditions.

Cultivars Levels 2007/2008 2008/2009

1st 22/1 2nd8/2 3rd 22/2 4th 9/3 5th 24/3 XX 1st 22/1 2nd8/2 3rd 22/2 4th 9/3 5th 24/3 XX

Giza 3 Natural 1.000 2.500 3.200 4.000 5.330 3.206 0.00 1.110 2.220 3.477 6.777 2.717

Protected 0.000 0.440 0.870 1.180 2.000 0.898 0.00 0.370 0.740 1.480 2.850 1.088

Giza 716 Natural 0.000 1.000 1.990 2.330 3.550 1.774 0.00 0.740 2.481 2.777 4.110 2.021

Protected 0.000 0.000 0.000 0.000 1.700 0.340 0.00 0.00 0.00 0.00 2.667 0.533

Giza 40 Natural 1.300 2.950 3.730 4.500 8.860 4.268 0.00 2.147 4.440 8.00 11.850 4.687

Protected 0.000 1.200 2.000 2.900 3.850 1.990 0.00 1.110 2.072 2.667 5.000 2.170

Sakha 1 Natural 1.000 1.345 3.900 4.300 7.852 3.676 0.00 0.740 3.00 3.330 9.000 3.214

Protected 0.000 0.000 1.820 2.420 3.000 1.448 0.00 0.00 0.740 1.110 3.667 1.103

Sakha 2 Natural 0.000 1.220 2.880 3.000 4.850 2.386 0.00 1.850 4.00 4.293 4.627 2.954

Protected 0.000 1.000 1.500 2.000 2.667 1.433 0.00 1.407 2.74 2.740 2.867 1.951

L.S.D. at 0.05: A = 1.145 B = 0.448 AB = 1.002 C = 0.501 AC = 1.120 BC = 1.002 ABC = 2.240 A = 0.329 B = 0.226 AB = 0.504 C = 0.252 AC = 0.564 BC = 0.504 ABC = 1.127. A, cultivar; B, level; AB, cultivar x level; C, period; AC, cultivar x period; BC, level x -period; ABC, cultivar x level x period.

Table 3 Area under disease progress curve (AUDPC), seed yield and losses percentages of four faba bean cultivars in two seasons (2007/08 and 2008/09), under field conditions.

Broad bean cultivars AUDPC Yield of plots Yield loss% than Dithane M45

Natural infection Protected Natural infection Protected Natural infection Protected

2007/2008 season

Giza 3 Mohassen 677.35 492.95 2.63 3.65 27.79 -

Giza 716 508.877 348.05 2.86 3.52 18.66 -

Giza 40 836.753 621.027 1.83 2.83 35.50 -

Sakha 1 715.75 507.15 2.31 3.45 32.82 -

Sakha 2 617.177 454.403 3.03 3.93 22.95 -

2008/2009 season

Giza 3 Mohassen 147.380 60.23 3.34 3.97 15.62 -

Giza 716 120.78 20.00 3.46 4.28 12.53 -

Giza 40 262.68 125.25 2.54 3.21 20.32 -

Sakha 1 173.55 55.25 2.59 3.15 17.46 -

Sakha 2 186.85 124.80 3.55 3.85 13.17 -

A = cultivar B = levels of inoculum A x B = varieties x levels.

under the protected plots in the first season, respectively. While in second season the same two cvs. the weight of pods/plants were (43.67 and 46.33) and (54.33 and 58.00 g/ plant). Weight of 100 seeds was significantly in each season were (79.67 and 83.33), (83.67 and 84.00), (87.33 and 90.67) and (88.00 and 86.67 g) in the two seasons for two cvs. Giza 716 and Sakha 1, respectively.

Simple regression analysis between AUDPC (Y) and each yield (X,) and loss% (X2)

Results in Table 5 indicated that the yield of five cultivars was significantly affected with AUDPC in two seasons. Correlation coefficient (y) values were -0.967, -0.988, -0.949, -0.925 and -0.940 in the first season 2007/08 and -0.944, -0.920, -0.936, -0.938 and -0.715 in the second season 2008/09 for the cultivars, Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2. The values of coefficient of determination (R2) indicated that 97.6% of the losses in seed yield of the cultivar Giza 716 was due to the effect of chocolate spot infection estimated as AUDPC on the yield loss% in two seasons. While, for Sakha 2, Sakha 1, Giza 3 Mohassen and Giza 40, R2 values were 0.966, 0.951, 0.929 and 0.845, respectively, in 2007/08. In the second season 2008/09 R2 values were 97.4%, 97.2%, 87.6%, 84.8% and 65.0% for Giza 40, Sakha 1, Giza 3 Mohassen, Giza 716 and Sakha 2, respectively which mean that 97.4%, 97.2%, 87.6%, 84.8% and 65.0% of the yield loss due to the disease.

Simple regression analysis between disease severity% (Y) and some other plant characters (X,-X5)

Results in Tables 6 and 7 indicated that, plant height (X1), number of branches/plant (X2), number of pods/plant (X3), weight of pods/plant (X4) and weight of seeds/plant (X5) were highly negative significant correlated with severity of infection ( Y) for Giza 3 Mohassen, Giza 716, Giza 40 and Sakha 1 in two seasons. However, for the cultivars Giza 716 and Sakha 2 no significant correlation was found for height of plant (X1) and number of branches (X2) for two seasons 2007/08 and 2008/09. The highest negative (r) values were found between disease severity ( Y) and weight of pods (X4) for the Giza 40 cv. followed by Giza 3

Mohassen, the (r) values were (—0.870 and —0.924 ) and (—0.803 and —0.916 ) in the two seasons, respectively. While (r) were (—0.794** and —0.584**) and (—0.894** and —0.820**) for Giza 716 and Sakha 1. The highest negative (r) value were found between disease severity (Y) and weight of 100 seed (X5) (—0.883** and —0.903**) for Sakha 2 in the two seasons, respectively. Also regression coefficient (b) values were found negative and significant for number of pods (X3) (—0.532 and —0.096), weight of pods (X4) (0.422** and —0.013**) and weight of 100 seed (X5) (—0.753** and —0.093**) for Giza 716 and (—0.644** and 0.226**), (—0.115** and —0.640**) and (0.159** and 0.222**) for Giza 40 for X3, X4 and X5 in the two seasons, respectively. Coefficient of determination (R2) values were 0.63 and 0.341 for Giza 716 and were 0.757 and 0.854 for Giza 40 for the weight of pods (X4) in the two seasons, respectively.

Discussion

Faba bean (Vicia faba L.) is consider as an old legume food grow on a large areas in the world, the crop great nutritional value for both human and animal consumption having a high content of protein, about (28%). Chocolate spot disease is the most important disease affecting faba bean plants in Egypt causing considerable reduction in seed yield. The objective of this research was to determine the amount of losses in seed yield of the main five faba bean cultivars under different levels of chocolate spot obtained by natural and protection with Dithane M45. Results revealed that the in vitro effect of the tested concentrations of Dithane M45, Galben manozeb 584 and copper oxychloride on the growth of B. fabae. It is clear that Dithane M45 were active where it decreased the fungal growth compared to check treatment followed by Galben manozeb. This results is in harmony with Abou-Zeid et al. (1990). Disease severity percentage on the tested cultivars was reduced when the fungicide Dithane M45 was applied 2 days before inoculation. These results are in agreement with those reported by Heweidy (1998) and Ibrahim et al. (1965), who stated that a protective control measure by fungicidal treatment would be feasible practices for controlling the disease.

Table 4 Severity of chocolate spot infection and some plant characters of four faba bean cultivars, under field conditions, 2007/08 and 2008/09 seasons.

Broad bean cultivars

Giza 3 Mohassen Giza 716

Disease record Disease severity% Plant height (cm)

No. of branches No. of pods

Weight of pods (gm) Weight of 100 seeds (gm)

2007/08 2008/09 2007/08 2008/09 2007/08 2008/09 2007/08 2008/09 2007/08 2008/09 2007/08 2008/09

Giza 40

Sakha 1

Sakha 2

L.S.D.

Natural

infection

Protected

Natural

infection

Protected

Natural

infection

Protected

Natural

infection

Protected

Natural

infection

Protected

at 0.05

31.00 27.67

25.33 45.33

34.67 35.33

29.33 34.67

27.67 1.78

3.00 4.00

3.00 12.00

5.00 9.00

3.67 4.33

3.00 0.65

101.33

104.67 112.33

119.00 101.67

107.67 100.33

99.67 103.00

102.67 2.211

106.67 113.33

118.67 98.00

102.33 94.00

97.33 94.67

108.00 2.668

2.33 2.67

2.67 2.00

3.00 2.00

2.33 2.67

2.67 0.445

2.67 2.33

2.33 1.67

1.67 1.67

2.00 1.67

2.67 0.459

14.67 12.67

16.33 11.00

13.33 8.67

12.00 12.00

15.33 0.643

21.00 22.00

23.33 18.00

15.67 19.33

23.00 26.00

28.33 0.752

50.00 41.00

49.33 35.33

41.00 38.33

43.33 46.67

51.00 0.997

53.00 45.00

54.33 39.67

43.33 47.33

50.33 58.00

58.00 1.519

67.33 79.67

87.33 57.00

61.00 71.33

73.00 83.67

88.00 1.412

75.67 83.33

90.67 61.67

66.67 71.67

76.33 84.00

86.67 2.827

Table 5 Simple regression analysis between (Y) AUDPC and seed of yield and loss%.

Season plant characters Giza 3 Mohassen Giza 716 Giza 40 Sakha 1 Sakha 2

r b R2 r b R2 r b R2 r b R2 r b R2

2007/08 Seed yield -0.967** -0.0196 0.935 -0.988** -0.0196 0.976 -0.949** -0.0359* 0.900 -0.925** -0.383 0.856 -0.940** -0.236 0.884

2008/09 -0.944** -0.01** 0.891 -0.920** -0.815 0.846 -0.936** -0.0176 0.876 -0.938** 0.0118** 0.879 -0.715** 0.142 0.511

2007/08 Losses% 0.964** 0.278** 0.929 0.988** 0.278** 0.976 0.919** -0.949 0.845 0.975** 0.786** 0.951 0.983** 0.852** 0.966

2008/09 0.936 3.716* 0.876 0.921** 3.689 0.848 0.932 2.849 0.974 0.986** 0.102** 0.972 0.806** 0.106 0.650

* p<0.05. ** p<0.01.

Table 6 Simple regression analysis between (Y) severity of infection and some plant characters (X) of five cultivars in season 2007/08.

Plant characters Giza 3 Mohassen Giza 716 Giza 40 Sakha 1 Sakha 2

r b R2 r b R2 r b R2 r b R2 r b R2

Plant height (Xj) -0.812** -0.131 0.659 -0.818 0.139 0.669 -0.744** 0.693 0.554 -0.271 0.313* 0.073 -0.673* -0.038 0.453

No. of branches (X2) -0.709** 0.219 0.503 -0.520 0.490 0.270 -0.293** 0.725 0.086 -0.670 0.584 0.449 -0.609** -0.175 0.371

No. of pods (X3) -0.928** -0.39 0.861 -0.837** -0.226 0.700 -0.829** -0.460 0.687 -0.914** 0.045 0.835 -0.950** -0.827 0.903

Weight of pods (X4) -0.917** 0.256 0.841 -0.825** 0.0213 0.681 -0.858** -0.428 0.736 -0.952** -0.136* 0.906 -0.807** 0.346 0.651

Weight of seed (X5) -0.904** -0.980 0.817 -0.901** 0.762 0.812 -0.856 -0.458 0.733 -0.918** 0.078 0.843 -0.909** -0.445 0.826

p<0.05. '* p<0.01.

Table 7 Simple regression analysis between (Y) severity of infection and some plant characters (X) of five cultivars in season 2008/09.

Plant characters Giza 3 Mohassen Giza 716 Giza 40 Sakha 1 Sakha 2

r b R2 r b R2 r b R2 r b R2 r b R2

Plant height (X1) -0.847** 0.023 0.717 -0.889 -0.174 0.790 -0.921* -0.112 0.848 -0.308** 0.272** 0.095 -0.533 0.229 0.284

No. of branches (X2) -0.692** -0.607 0.479 -0.504 -0.868 0.254 -0.507** 0.421 0.257 -0.728** -0.163 0.530 -0.381** 0.014 0.145

No. of pods (X3) -0.962** -0.276 0.925 -0.915** -0.656** 0.837 -0.977* -0.417 0.955 -0.892** -0.218 0.796 -0.809** -0.229 0.654

Weight of pods (X4) -0.910** -0.047 0.828 0.872** -0.397* 0.760 -0.943** -0.111 0.889 -0.767** 0.850** 0.588 -0.842** -0.269 0.710

Weight of

seed (X5) -0.959** -0.300 0.920 80.825** 0.169* 0.681 0.955 0.043 0.912 -0.862** -0.370 0.743 -0.817 -0.109 0.663

* p<0.05. ** p<0.01.

The effect of different infection severity on yield was studied in field plots using the cvs. Giza 716 and Sakha 2 (Moderately susceptible), Giza 3 Mohassen (susceptible) and Giza 40 and Sakha (highly susceptible) in two seasons (2007/08 & 2008/09). It was observed that the infection was started in the two seasons growing in the same date first core at January 24, but is was highly value in the first than the second season. This is mainly due to late rain in the first season, with lower temperature degrees. Nassib et al. (1991) mentioned that, late rain in certain seasons increase relative humidity and wetness which leads to epiphytotic conditions.

Severity of infection was reduced by the application of fungicide Dithane M45, compared to the naturally

Higher values of AUDPC were accompanied with lower yield. This was true for five tested cultivars in both two seasons. The reduction in seed yield (loss%) of the cultivar 716 reached 18.66% naturally infected plots compared to the protected plots in the first season, while in second season it was only 12.53%. In case of the cv. Giza 40 losses% in seed yield were 33.5% and 20.32% in the two seasons, respectively, while the cv. Giza 3 Mohassen showed 27.79% and 15.62% losses in the two seasons. Earlier studying of Bekhit and Rizk (1970), Mansour and Kamel (1975), Mansour et al. (1975) and Nassib (1983), reported that three or four times spraying with Dithane M45 starting mid-January was very effective in controlling chocolate spot in field bean and led to a significant increase in seed yield. This is agreement with Rizk (1974) who mentioned that losses caused by chocolate spot disease ranged from 40% to 50% of the yield in the years of sever attack, and from 5% to 15% in the years of mold infection. Williams (1975) found that the yield of healthy plants was higher by 27% than the inoculated plots with the pathogen 6 weeks after emergence. Also, Abd El-Hak et al. (1984) found the seed yield loss due to chocolate spot disease was 58%.

Negative correlation (r) values were significantly between the AUDPC of five tested cultivars and the seed yield. The values by which the loss percent increased for each unit of the AUDPC, could be obtained as the b values, regression coefficient of each cultivar. This were 0.959, 0.788 and 0.852 for Giza 40, Sakha 1 and Sakha 2in 2007/08 season, respectively. While in the second season 2008/09 b values were 2.849, 0.102 and 0.106 for the three same cultivars, respectively. Coefficient of determination R2 values which indicated the values of the effect of the infection on loss% were obtained. R2 values for Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2 in 2007/08 season were 0.929%, 0.976%, 0.845%, 0.951% and 0.966%, respectively, these means, that yield loss of the five cultivars were due to the infection as AUDPC by 92.9%, 97.6%, 84.5%, 95.1% and 96.6% for the five cultivars, respectively. While in 2008/09 season these were 87.6%, 84.8%, 97.4%, 97.2% and 65.0%. The coefficient of determination R2 values indicated that the first two characters were less affected by the infection than the other three characters, for the five cultivars studied. This may indicate the importance of number and weight of pods/plant and weight of seed/plant rather than other characters. The effect of severity of infection on weight of pods were obtained from R2 values of each cultivar. These were 0.645%, 0.630%, 0.757%, 0.815% and 0.799% for Giza 3 Mohassen, Giza 716, Giza 40, Sakha 1 and Sakha 2, respectively, in the first season and were 0.839%, 0.341%, 0.854%, 0.530% and 0.672% for the same cultivars in the second season 2008/09. This means that

(64.5% and 83.9%) of the reduction in weight of pod of the

cultivar Giza 3 Mohassen were due to the severity of infection

in the two season, respectively.

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