Abstract: Present objective was to study this phenomenon on the common seed-borne fungi of faba bean in soil amended with composted organic wastes and infested with the most commonly isolated fungi from Vicia faba seed. In vitro studies showed that the yeast was effective in reducing the linear growth of Cephalosporium sp., F. verticillioides, F. oxysporum,. F. solani, R. solani and V. dahliae. Pre- and post-emergence damping-off caused by Cephalosporium sp., F. verticillioides, F. oxysporum, F. solani, R. solani and V. dahliae was reduced significantly when seeds of faba bean were coated with a water suspension (109 cfu mL-1) of the yeast before sowing in soil supplemented with compost type (1) (prepared by Mansoura manufacturer with organic waste from city garbage) or type (2) (consisted of 1 ton of horticultural waste and 100 kg sheep manure). Soil was artificially infested with the fungi isolated from faba bean seeds. The above treatment significantly increased plant growth parameters including height, shoot and root length, number of branches/plant, number of pods/plant, pod weight/plant, fresh weight and dry weight. Photosynthetic pigments (chlorophyll A, chlorophyll B and carotenoids) were also increased by the treatments. Total phenols content in the treated plant leaves was higher than in the control plants.
INTRODUCTION
Vicia faba, which has several common names (broad bean, fava bean, faba bean, horse bean, field bean, tic bean), is a species of bean (Fabaceae) native to North Africa and Southwest Asia and is extensively cultivated elsewhere.
This crop is subjected to numerous injuries and stresses which interfere with growth and development. Many fungi are serious pathogens on flowers and seeds, reducing seed yield both qualitatively and quantitatively. Other fungi, including saprophytes and very weak parasites, may lower seed quality. The most common seed-borne fungi on faba bean are: Ascochyta fabae, the cause of leaf and pod spot; Botrytis cinerea, the cause of grey mould; Botrytis fabae, the cause of chocolate spot; Fusarium sp., the cause of foot rot and wilts and Rhizoctonia solani, the cause of damping-off of seedlings. Seed abortion, shrunken seeds, reduction in seed size, seed rot, seed necrosis, seed discoloration, reduction in germination capacity and physiological alterations in seed are caused by these pathogens (Neergaard, 1979).
Certain yeasts possess many features which make them favourable as biocontrol agents (Wilson and Wisniewski, 1989). Gianluca et al. (2006) isolated antagonistic yeasts from the epiphytic flora associated with grape berries. The yeasts showed biological control of Aspergillus carbonarius and A. niger, which produce Ochratoxin A in grape. Lassois et al. (2008) reported the antagonistic activity of two yeast strains, Pichia anomala and Candida oleophila, on the parasitic complex of banana crown rot.
Composts have been found to be effective as biocontrol agents of various plant pathogens under field conditions (Keener et al., 2000). Ioanna et al. (2008) found that no chemical control method was adequate to control the soil-borne fungus Verticillium dahliae. Management strategies were focused on preventive measures, utilizing microbes to suppress V. dahliae. Eggplants grown in sterilized or non-sterilized compost were transplanted to soil infested with V. dahliae microsclerotia, amended or not with sterilized or non-sterilized compost. The most effective treatments were those that included non-sterilized compost; therefore, the observed suppression of V. dahliae could be attributed to microbial agents.
Several microbes were isolated from the root system of eggplants grown in the compost and tested in vitro against V. dahliae. Two bacterial strains were identified as members of the Pseudomonas fluorescens complex and two fungal isolates of Fusarium oxysporum were selected for further evaluation under glasshouse conditions. The ability of the microbial agents to reduce the percentage of diseased leaves compared to the control treatment was demonstrated.
This study was undertaken to evaluate the effect of bread yeast in suppressing the most common seed-borne pathogens of faba bean in the presence of soil amended with composted organic household wastes and yard trimmings.
MATERIALS AND METHODS
Isolation and identification of yeast: Saccharomyces cerevisiae (Meyen ex E.C. Hansen) was isolated on malt extract agar medium (MEA), identified in the Microbiology Department, Faculty of Agriculture, Mansoura University and tested for its antagonistic effects against the following seed-borne fungi of faba bean: Cephalosporium sp., F. oxysporum, F. solani, F. verticillioides, R. solani and V. dahliae.
In vitro agar plate bioassays: The isolated yeast was assayed in vitro for inhibition of the six pathogenic fungi. Initial inhibition assays were conducted on PDA plates with single streaks of yeast drawn across the plate's centers. After 2-3 days growth at 20-25°C, PDA discs of 0.5 cm diameter were taken from the margins of growing pathogen colonies and placed on either sides of the yeast streaks at a distance of 30 mm, then incubated for an additional 4-6 days at 20-25°C. The distance was measured from the fungal colony center to its edge nearest the yeast streak. This was compared to the growth of a non-streaked control to determine the degree of inhibition of pathogen growth (Wang et al., 2003). Three replicates were used for each pathogen.
Effect of S. cerevisiae combined with composted organic materials on the seed-borne pathogenic fungi of faba bean plants under greenhouse conditions: Two types of compost were used; Compost (1) which was prepared by Mansoura manufacturer for organic manure from city garbage and Compost (2) which consisted of 1 ton of horticultural waste and 100 kg sheep manure. Chemical and physical analyses of these composts were performed at the Mansoura manufacturer for compost (1) and at the Faculty of Agriculture, Mansoura University for compost (2). The results are shown in Table 1.
| Table 1: | Chemical and physical analysis of the two types of compost |
An experiment was conducted to determine the effect of the composted organic materials enriched with the yeast S. cerevisiae on the six pathogenic fungi. S. cerevisiae was applied as a seed dressing to the faba bean seeds. Three flasks containing two-days-old liquid cultures of S. cerevisiae were used. Seeds were coated with an adhesive material (acacia gum) before treatment. Yeast-coated seeds contained about 109 cfu seed-1 (Weller and Cook, 1983).
Eighteen plastic pots (25 cm diameter) containing sterilized sandy loam soil were used for each fungus. Three replicates (pots) were used for each treatment as follows:
| • | Control (non-amended soil, non-treated seeds) |
| • | Compost type (1) treated soil, non-treated seeds |
| • | Compost type (2) treated soil, non-treated seeds |
| • | Yeast (non-amended soil, S. cerevisiae treated seeds) |
| • | Compost type (1) treated soil, S. cerevisiae treated seeds |
| • | Compost type (2) treated soil, S. cerevisiae treated seeds |
Each type of compost was added to the pots at the rate of 25 g/pot. The treatments were inoculated separately with each fungal preparation at the rate of 5% (w/w). Pots were kept in a greenhouse for 7 days at 22±5°C to allow the fungi to adapt before sowing seeds. During that period, the soil was moistened when necessary. Seeds were coated with a yeast suspension taken from 3-days-old liquid cultures. Five seeds were planted in each pot. Control pots were prepared similarly but were pathogen-free.
The numbers of pre- and post-emergence damping off and stunted seedlings, as well as healthy plants, were recorded after 15, 30 and 45 days. Growth parameters including plant height (cm), root length (cm), shoot length (cm), number of branches (branch/plant), number of pods (pod/plant), pod weight (g), fresh weight (g) and dry weight (g) were recorded after 60 days. Photosynthetic pigments (mg g-1 fresh weight) and total phenols (mg catechol/100 g fresh weight) were measured.
Estimation of photosynthetic pigments content: The spectrophotometric method recommended by Metzner et al. (1965) was used in this investigation. A definite weight of fresh leaves was homogenized immediately after harvesting in 5 mL cold aqueous acetone (85%), kept overnight in a refrigerator and then centrifuged. The supernatant, which contained the pigments, was diluted with cold aqueous acetone to an appropriate volume for spectrophotometric measurements. The extract was measured against blanks of pure 85% acetone solution at three wavelengths: 452, 644 and 663 nm. The concentration of each pigment, chlorophyll A (Chl. A), chlorophyll B (Chl. B) and carotenoids (Carot.), was determined by using the following equations:
Chl. A = 10.3 E663-0.918 E644 |
Chl. B = 19.7 E644-3.87 E663 |
Carot. = 4.2 E452-(0.0264 Chl. a + 0.426 Chl. b) |
Estimation of total phenols content: Total phenols were determined using the Folin-Ciocalteau reagent (Singleton and Rossi, 1965). To determine the calibration curve, 1 mL aliquots of 0.02, 0.04, 0.06, 0.08 and 1.00 mg mL-1 ethanolic catechol solutions were combined with 0.5 mL Folin-Ciocalteau reagent. After 3 min, 2 mL (200 g L-1) sodium carbonate was added and the contents were mixed thoroughly. The final color change was measured calorimetrically at 650 nm using a SPEKOL11 Carl Zeiss photometer and the calibration curve was drawn.
Fresh leaf samples (2 g) were homogenized in 80% aqueous ethanol at room temperature and centrifuged in cold at 10,000 rpm for 15 min and the supernatant was saved. The residues were re-extracted twice with 80% ethanol and the supernatants were pooled, put in evaporating dishes and evaporated to dryness at room temperature. Residues were dissolved in 5 mL of distilled water. One hundred microlitres of this extract was diluted to 3 mL with water and mixed with the same amount of reagents as described above. The color was developed and absorbance measured after 60 min. The results were expressed as mg catechol/100 g fresh weight material. All determinations were replicated three times. Total content of phenolic compounds in plant ethanolic extracts was calculated as catechol equivalents by the following equation:
Where:
| T | : | Total content of phenolic compounds, in mg of catechol/100 g of fresh weight material |
| c | : | The concentration of catechol established from the calibration curve, in mg mL-1 |
| V | : | The volume of extract in mL |
| m | : | The weight of pure plant ethanolic extract in g |
Statistical analysis: Data were subjected to analysis of variance by Duncan’s multiple range tests using SAS version 6.11 (Duncan, 1995).
RESULTS
Effect of S. cerevisiae isolated yeast from compost on seed-borne pathogenic fungi of faba bean plants under greenhouse conditions: The following pathogenic fungi were used in this investigation: Cephalosporium sp., F. verticillioides, F. oxysporum, F. solani, R. solani and V. dahliae.
In vitro agar plate bioassays: Data presented in Table 2 show the degree of fungal inhibition due to the effect of isolated yeast; Cephalosporium sp. had linear growth of 1.35 cm, F. verticillioides had 0.97 cm, F. oxysporum had 0.77 cm, F. solani had 1.80 cm, R. solani had 0.97 cm and V. dahliae had 0.87 cm.
Effect of S. cerevisiae combined with tested composts on faba bean seeds grown in pathogen-infested soil under greenhouse conditions: Faba bean seeds coated with S. cerevisiae were grown in soil supplemented with compost type (1) or type (2). Soil was infested with the fungal isolates. The results showed decreases in pre- and post-emergence damping-off and stunted seedlings (Table 3-5).
Data in Table 3 show that seed treatment with S. cerevisiae significantly reduced the amount of pre-emergence damping-off due to the presence of following fungi in soil: F. oxysporum and F. solani (50.00%), F. verticillioides (25.00%), R. solani (33.32%) and V. dahliae (25.00%).
Data in Table 4 show that the treatment in which compost type (1) was added to soil and seeds were coated with S. cerevisiae significantly reduced pre-emergence damping-off caused by R. solani (66.68%), Cephalosporium sp. (50.00%), F. verticillioides (62.50%), F. oxysporum (50.00%), F. solani (50.00%) and V. dahliae (50.00%).
| Table 2: | Antagonistic effect of isolated yeast on linear growth of tested pathogenic fungi in vitro |
| Control: No antagonist yeast. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 3: | Effect of S. cerevisiae on seedling survival of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Healthy seeds planted as non-coated seeds. Yeast: Healthy yeast-coated seeds planted in pathogen-infested soil. Reduction (%) = Yeast- Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 4: | Effect of compost type (1) combined with S. cerevisiae on seedling survival of faba bean plants grown in pathogen-infested-soil under greenhouse conditions |
| Control: Healthy seeds planted in non-treated soil and non-coated seeds. S. cerevisiae +compost 1: Healthy yeast coated seeds planted in pathogen-infested and compost type (1) treated soil. Reduction (%) = S. cerevisiae +compost type (1)-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 5: | Effect of compost type (2) combined with S. cerevisiae on seedling survival of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Healthy seeds planted in non-treated soil (non-coated seeds). S. cerevisiae +compost (2): Healthy yeast-coated seeds planted in pathogen-infested and compost type (2) treated soil. Reduction (%) = S. cerevisiae +compost type (2)-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
Data in Table 5 show that the addition of compost type (2) with S. cerevisiae significantly reduced pre-emergence damping-off caused by F. verticillioides (88.00%), Cephalosporium sp. (50.00%), F. oxysporum (50.00%), F. solani (83.32%), R. solani (83.32%) and V. dahliae (75.00%).
Data in Table 3 show that seed treatment with S. cerevisiae significantly reduced post-emergence damping-off caused by F. solani (50.00%), Cephalosporium sp. (33.35%) and R. solani (40.00%). F. verticillioides, F. oxysporum and V. dahliae were not affected by the yeast.
Data in Table 4 show that compost type (1) in the presence of S. cerevisiae significantly reduced post-emergence damping-off caused by F. solani (100%), Cephalosporium sp. (66.65%), F. oxysporum (33.35%) and R. solani (60.00%). F. verticillioides and V. dahliae were resistant to the antagonistic properties of S. cerevisiae.
Data in Table 5 show that compost type (2) in the presence of S. cerevisiae significantly reduced post-emergence damping-off caused by F. verticillioides, F. oxysporum and R. solani (100%) compared with other pathogenic fungi: Cephalosporium sp. (66.65%), F. solani (75.00%) and V. dahliae did not react to S. cerevisiae.
Data in Table 3 show that seed treatment with S. cerevisiae significantly reduced the number of stunted seedlings due to V. dahliae (40.00%), Cephalosporium sp. (20.00%), F. verticillioides (25.00%), F. oxysporum (33.35%) and R. solani (33.35%). F. solani was not affected by S. cerevisiae.
Data in Table 4 show that compost type (1) in the presence of S. cerevisiae significantly reduced the number of stunted seedlings caused by F. solani (100%), as compared with Cephalosporium sp. (80.00%), F. verticillioides (75.00%), F. oxysporum (33.35%), R. solani (66.65%) and V. dahliae (60.00%).
Data in Table 5 show that compost type (2) added to soil in the presence of seed coated with S. cerevisiae significantly reduced the number of stunted seedlings caused by F. oxysporum (100%), as compared with Cephalosporium sp. (80.00%), F. verticillioides (66.65%), F. solani (50.00%), R. solani (33.35%) and V. dahliae (80.00%).
Effect of S. cerevisiae combined with tested composts on the growth parameters of faba bean plants grown in pathogen-infested soil under greenhouse conditions: In this experiment faba bean seeds coated with S. cerevisiae and grown in soil amended with compost type (1) and (2) showed an increase in various growth parameters (plant height, shoot length, root length, number of branches/plant, number of pods/plant, pod weight/plant, fresh weight and dry weight) when compared with non-coated seeds (Table 6-8).
Plant height (cm): Data in Table 6 show an increase in plant height in the treatment where S. cerevisiae was used and soil was infested with R. solani, with an average height of 88.46 cm, while Cephalosporium sp. averaged 79.60 cm, F. verticillioides 78.50 cm, F. oxysporum 84.33 cm, F. solani 82.23 cm and V. dahliae 79.10 cm.
Data in Table 7 show an increase in plant height in the treatment where compost type (1) was added to the soil and seeds were coated with S. cerevisiae in soil infested with R. solani, with an average height of 92.76 cm, while Cephalosporium sp. averaged 86.26 cm, F. verticillioides 92.26 cm, F. oxysporum 87.86 cm, F. solani 86.66 cm and V. dahliae 88.00 cm.
Data in Table 8 show an increase in plant height in the treatment where compost type (2) was added to the soil and seeds were coated with S. cerevisiae in soil infested with F. oxysporum, with an average height of 91.80 cm, while Cephalosporium sp. averaged 83.50 cm, F. verticillioides 95.00 cm, F. solani 91.33 cm, R. solani 87.70 cm and V. dahliae 88.00 cm.
Shoot length (cm): Data in Table 6 show an increase in shoot length in the treatment where faba bean seeds coated with S. cerevisiae were sown in soil infested with R. solani. The average length was 64.66 cm, while Cephalosporium sp. averaged 57.60 cm, F. verticillioides 60.00 cm, F. oxysporum 61.00 cm, F. solani 59.56 cm and V. dahliae 59.00 cm.
Data in Table 7 show that the treatment of compost type (1) and S. cerevisiae in the presence of R. solani significantly increased shoot length to an average 68.80 cm, while Cephalosporium sp. averaged 66.93 cm, F. verticillioides 68.26 cm, F. oxysporum 63.20 cm, F. solani 61.83 cm and V. dahliae 61.46 cm.
| Table 6: | Effect of S. cerevisiae on growth parameters of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds. S. cerevisiae: Yeast-coated seeds planted in pathogen-infested soil. Increase (%) = S. cerevisiae-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 7: | Effect of compost type (1) combined with S. cerevisiae on growth parameters of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds planted in non-treated soil. Compost (1) + S. cerevisiae: Healthy yeast-coated seeds planted in pathogen-infested and compost type (1) treated soil. Increase (%) = Compost (1)+ S. cerevisiae-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 8: | Effect of compost type (2) combined with S. cerevisiae on growth parameters of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds planted in non-treated soil. Compost (2) + S. cerevisiae: Healthy yeast-coated seeds planted in pathogen-infested and compost type (2) treated soil. Increase (%) = Compost (2) + S. cerevisiae-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
Data in Table 8 show that the treatment of compost type (2) in the presence of S. cerevisiae significantly increased average shoot length where soil was infested with R. solani to 66.00 cm, while Cephalosporium sp. averaged 65.13 cm, F. verticillioides 65.33 cm, F. oxysporum 64.46 cm, F. solani 64.46 cm and V. dahliae 60.00 cm length.
Root length (cm): Data in Table 6 show an average increase in root length in the treatment where S. cerevisiae was used and soil infested with Cephalosporium sp. of 22.00 cm, while F. verticillioides averaged 18.50 cm, F. oxysporum 23.33 cm, F. solani 22.66 cm, R. solani 23.80 cm and V. dahliae 20.10 cm.
Data in Table 7 show an average increase in root length of faba bean plants grown in soil supplemented with compost type (1) when seeds were coated with S. cerevisiae and soil was infested with V. dahliae of 26.60 cm, while Cephalosporium sp. averaged 19.33 cm, F. verticillioides 24.00 cm, F. oxysporum 24.66 cm, F. solani 24.83 cm and R. solani 23.96 cm.
Data in Table 8 show an average increase in root length in the treatment where compost type (2) combined with S. cerevisiae was used with soil infested with V. dahliae of 28.00 cm, while Cephalosporium sp. averaged 19.00 cm, F. verticillioides 29.66 cm, F. oxysporum 27.33 cm, F. solani 26.86 cm and R. solani 27.60 cm.
Number of branches (branches/plant): Data in Table 6 show an increase in the average number of branches in the treatment where S. cerevisiae was used and soil infested with V. dahliae of 2.63 branches/plant, while Cephalosporium sp. averaged 2.33 branches/plant, F. verticillioides 2.16 branches/plant, F. oxysporum 2.00 branches/plant, F. solani 2.66 branches/plant and R. solani 2.33 branches/plant.
Data in Table 7 show an increase in the average number of branches in the treatment where compost type (1) combined with S. cerevisiae was used in soil infested with V. dahliae of 2.86 branches/plant, while Cephalosporium sp. averaged 2.66 branches/plant, F. verticillioides 2.93 branches/plant, F. oxysporum 2.33 branches/plant, F. solani 2.86 branches/plant and R. solani 2.53 branches/plant.
Data in Table 8 show an increase in the average number of branches in the treatment where soil was supplemented with compost type (2), S. cerevisiae was used and the soil infested with R. solani of 2.73 branches/plant, while Cephalosporium sp. averaged 2.66 branches/plant, F. verticillioides 3.23 branches/plant, F. oxysporum 2.66 branches/plant, F. solani 2.73 branches/plant and V. dahliae 2.73 branches/plant.
Number of pods (pods/plant): Data in Table 6 show an increase in the average number of pods in the treatment where S. cerevisiae was used and soil infested with R. solani of 4.00 pods/plant, while Cephalosporium sp. averaged 4.33 pods/plant, F. verticillioides 6.33 pods/plant, F. oxysporum 5.00 pods/plant, F. solani 5.00 pods/plant and V. dahliae 5.00 pods/plant.
Data in Table 7 show an increase in the average number of pods in the treatment of compost type (1) and S. cerevisiae with R. solani infested soil of 5.66 pods/plant, while Cephalosporium sp. averaged 4.66 pods/plant, F. verticillioides 5.33 pods/plant, F. oxysporum 5.66 pods/plant, F. solani 5.00 pods/plant and V. dahliae 6.00 pods/plant.
Data in Table 8 show an increase in the average number of pods in the treatment where compost type (2) and S. cerevisiae were used in soil infested with R. solani of 5.33 pods/plant, whild Cephalosporium sp. averaged 5.00 pods/plant, F. verticillioides 5.33 pods/plant, F. oxysporum 5.00 pods/plant, F. solani 5.66 pods/plant and V. dahliae 5.66 pods/plant.
Pod weight (g/plant): Data in Table 6 show an increase in average total pod weight in the treatment where S. cerevisiae was used and soil infested with F. solani of 8.00 g/plant, while Cephalosporium sp. averaged 7.40 g, F. verticillioides 12.00 g, F. oxysporum 10.86 g, R. solani 8.10 g and V. dahliae 6.66 g.
Data in Table 7 show an increase in the average total pod weight in the treatment where compost type (1) and S. cerevisiae were used with soil infested with F. solani of 11.33 g/plant, while Cephalosporium sp. averaged 14.00 g, F. verticillioides 14.00 g, F. oxysporum 12.00 g, R. solani 12.93 g and V. dahliae 14.73 g.
Data in Table 8 show an increase in average total pod weight in the treatment where compost type (2) and S. cerevisiae were used in soil infested with V. dahliae of 12.70 g/plant, while Cephalosporium sp. averaged 11.06 g, F. verticillioides 13.70 g, F. oxysporum 12.60 g, F. solani 12.20 g and R. solani 10.00 g.
Fresh weight (g/plant): Data in Table 6 show an average increase in the fresh weight of faba bean plants in the treatment where S. cerevisiae was used and soil infested with F. verticillioides of 50.20 g, while Cephalosporium sp. averaged 38.10 g, F. oxysporum 52.23 g, F. solani 44.10 g, R. solani 50.66 g and V. dahliae 52.00 g.
Data in Table 7 show an average increase in fresh weight in the treatment where compost type (1) and S. cerevisiae were used with soil infested with F. verticillioides of 68.00 g, while Cephalosporium sp. averaged 53.06 g, F. oxysporum 57.06 g, F. solani 43.00 g, R. solani 70.50 g and V. dahliae 43.23 g.
Data in Table 8 show an average increase in fresh weight in the treatment where compost type (2) and S. cerevisiae were used in soil infested with F. verticillioides of 66.00 g, while Cephalosporium sp. averaged 48.53 g, F. oxysporum 66.20 g, F. solani 40.00 g, R. solani 56.30 g and V. dahliae 49.50 g.
Dry weight (g/plant): Data in Table 6 show an increase in average dry weight in the treatment where S. cerevisiae was used and soil infested with F. verticillioides of 13.10 g, while Cephalosporium sp. averaged 10.53 g, F. oxysporum 16.96 g, F. solani 11.20 g, R. solani 15.66 g and V. dahliae 10.00 g.
Data in Table 7 show an increase in average dry weight in the treatment where compost type (1) and S. cerevisiae were used in soil infested with F. verticillioides of 14.90 g, while Cephalosporium sp. averaged 10.00 g, F. oxysporum 17.43 g, F. solani 11.20 g, R. solani 16.83 g and V. dahliae 14.70 g.
Data in Table 8 show an increase in average dry weight in the treatment where compost type (2) and S. cerevisiae were used in soil infested with F. verticillioides of 14.70 g, while Cephalosporium sp. averaged 10.53 g, F. oxysporum 20.50 g, F. solani 10.20 g, R. solani 15.80 g and V. dahliae 12.86 g.
Effect of S. cerevisiae separately and combined with each compost on photosynthetic pigments and total phenols content of faba bean plants grown in fungi infested soil under greenhouse conditions.
Faba bean seeds coated with S. cerevisiae separately, as well as combined with compost type (1) and type (2) treated soil, were grown in soil infested with each fungus. The plants showed an increase in photosynthetic pigments (chlorophyll A, chlorophyll B and carotenoids) and total phenols content when compared with the control (Table 9-11).
Data in Table 9 show that chlorophyll A content increased when S. cerevisiae-coated seeds were planted in soil infested with R. solani by 70.11%, while the
increase was 32.43% with F. solani, 17.69% with Cephalosporium sp., 15.87% with F. verticillioides, 14.84% with F. oxysporum and 11.28% with V. dahliae.
Data in Table 10 show that chlorophyll A content increased in the S. cerevisiae+compost type (1) treatment in soil infested with R. solani by 65.52%, while the increase was 39.64% with F. solani, 19.23% with Cephalosporium sp., 15.87% with F. verticillioides, 13.28% with F. oxysporum and 12.78% with V. dahliae.
Data in Table 11 show that chlorophyll A content increased in the S. cerevisiae+compost type (2) treatment in soil infested with R. solani by 72.41%, while the increase was 30.63% with F. solani, 20.00% with Cephalosporium sp., 19.84% with F. verticillioides, 13.53% with V. dahliae and 13.28% with F. oxysporum.
Data in Table 9 show that chlorophyll B content increased when S. cerevisiae-coated seeds were planted in soil infested with R. solani by 73.53%, while the increase was 24.04% with Cephalosporium sp., 18.81% with F. verticillioides, 12.50% with F. oxysporum, 51.80% with F. solani and 11.93% with V. dahliae.
Data in Table 10 show that chlorophyll B content increased in the S. cerevisiae+compost type (1) treatment in soil infested with R. solani by 73.53%, while the increase was 51.80% with F. solani, 24.04% with Cephalosporium sp., 18.81% with F. verticillioides, 12.50% with F. oxysporum and 11.93% with V. dahliae.
Data in Table 11 show that chlorophyll B content increased in the S. cerevisiae+compost type (2) treatment in soil infested with R. solani by 85.29%%, while the increase was 48.19% with F. solani, 26.92% with Cephalosporium sp., 26.92% with F. oxysporum, 14.85% with F. verticilloides and 11.93% with V. dahliae.
Data in Table 9 show that carotenoids content increased when S. cerevisiae-coated seeds were planted in soil infested with R. solani by 68.42%, while the increase was 35.05% with F. solani, 11.11% with Cephalosporium sp., 9.01% with V. dahliae, 5.08% with F. oxysporum and 5.00% with F. verticillioides.
Data in Table 10 show that carotenoids content increased in the S. cerevisiae+compost type (1) treatment in soil infested with R. solani by 77.63%, while the increase was 34.02% with F. solani, 22.22% with Cephalosporium sp., 20.24% with F. oxysporum, 12.30% with V. dahliae and 8.33% with F. verticillioides.
| Table 9: | Effect of S. cerevisiae on photosynthetic pigments and total phenols content of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds. S. cerevisiae: Healthy yeast-coated seeds planted in pathogen-infested soil. Increase (%) = S. cerevisiae-Control/Control x 100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 10: | Effect of compost type (1) combined with S. cerevisiae on photosynthetic pigments and total phenols content of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds. Compost (1) + S. cerevisiae: Healthy yeast-coated seeds planted in compost (1) treated soil. Increase (%) = Compost (1)+ S. cerevisiae-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
| Table 11: | Effect of compost type (2) combined with S. cerevisiae on photosynthetic pigments and total phenols of faba bean plants grown in pathogen-infested soil under greenhouse conditions |
| Control: Non-coated seeds. Compost (2) + S. cerevisiae: Healthy yeast-coated seeds planted in compost (2) treated soil. Increase (%) = Compost (2)+ S. cerevisiae-Control/Controlx100. XMean within a column followed by the same letter(s) is not significantly different according to Duncan’s multiple range tests | |
Data in Table 11 show that carotenoids content increased in the S. cerevisiae+compost type (2) treatment in soil infested with R. solani by 69.74%, while the increase was 35.05% with F. solani, 14.53% with Cephalosporium sp., 14.40% with F. oxysporum, 12.50% with F. verticilloides and 9.83% with V. dahliae.
Data in Table 9 show that total phenols content increased when S. cerevisiae-coated seeds were planted in soil infested with F. oxysporum by 17.19%, while the increase was 10.76% with F. solani, 10.56% with Cephalosporium sp., 6.52% with R. solani, 3.33% with V. dahliae and 1.08% with F. verticillioides.
Data in Table 10 show that total phenols content increased in the S. cerevisiae+compost type (1) treatment in soil infested with Cephalosporium sp. by 25.55%, while the increase was 17.18% with F. oxysporum, 14.25% with F. solani, 11.54% with F. verticillioides, 8.00% with V. dahliae and 6.49% with R. solani.
Data in Table 11 show that total phenols content increased in the S. cerevisiae+compost type (2) treatment in soil infested with F. verticilloides by 50.61%, while the increase was 46.68% with F. solani, 22.38% with Cephalosporium sp., 22.26% with V. dahliae, 22.20% with F. oxysporum and 13.82% with R. solani.
DISCUSSION
The present study shows that the application of yeast as a bio-control agent affected all tested fungi in vitro. The percentage of inhibition reached 72% with Fusarium oxysporum when compared with the other pathogenic fungi and the control. These results are in agreement with Hassanein et al. (2002), who reported that yeasts were effective producers of antifungal metabolites. In addition, it was found that isolates of actinomycetes produced chitinase and β-1, 3 glucanase and caused extensive plasmolysis and cell wall lysis of Cephalosporium maydis in vitro. Since the cell wall of C. maydis consists largely of chitin and β-glucanase (Bartnicki-Garcia and Lippman, 1982), there is a voluminous body of literature on the ability of actinomycetes and fungi to parasitize spores, hyphae and other fungal structures. Many of these observations are linked with plant disease bio-control (Jeffries and Young, 1994; Van de Boogert and Deacan, 1994; Davanlou et al., 1999).
Weller (1988), Lee et al. (1991), Yuan and Crawford (1995), Valois et al. (1996), El-Tarabily et al. (1997), Youssef et al. (2001) and Gianluca et al. (2006) reported also that a microorganism that colonizes roots is ideal for use as a biocontrol agent against soil-borne diseases and, consequently, improving plant growth. Yeasts applied for the control of plant pathogens were found to produce proteinaceous killer toxins lethal to susceptible yeast and fungi strains (Hodgson et al., 1995; Abranches et al., 1997; Marquina et al., 2002; Santos et al., 2004).
Results obtained from this study showed that the addition of yeast as an antagonist improved disease suppression due to the compost and decreased disease severity (pre- and post-emergence damping-off and stunted seedlings). This result is supported by the finding of Postma et al. (2003) in which they concluded that the antagonist may enrich composts to increase the reliability of the beneficial effects of compost in disease suppressiveness.
In this study, the treatment of compost plus yeast increased plant growth. This result is supported by Kleifield and Chet (1992) and El-Mehalawy et al. (2004) who reported that the growth increase caused by rhizosphere microorganisms depended mainly on the ability of those microorganisms to survive and develop in the rhizosphere. In addition, several plant-microbe interactions were developed which benefited plant growth through different mechanisms, such as the production of plant regulators, siderophores, phosphate solubilization, nutrient uptake and availability (Hoflich and Kuhn, 1996; Gupta et al., 1998; Bowen and Rovira, 1999).
ACKNOWLEDGMENT
The authors thank Dr. Conrad J. Krass, Primary State Plant Pathologist, California Department of Food and Agriculture, Sacramento, CA, USA (retired) for critical review of the manuscript.