Subscribe Now Subscribe Today
Research Article
 

Control of Tomato Early Blight Disease by Certain Aqueous Plant Extracts



Nashwa M.A. Sallam
 
Facebook Twitter Digg Reddit Linkedin StumbleUpon E-mail
ABSTRACT

The objective of this work to study the effect of six plant extracts, Ocimum basilicum (Sweat Basil), Azadirachta indica (Neem), Eucalyptus chamadulonsis (Eucalyptus), Datura stramonium (Jimsonweed), Nerium oleander (Oleander) and Allium sativum (Garlic) against Alternaria solani in vitro and in vivo. In in vitro study the leaf extracts of D. stramonium, A. indica and A. sativum at 5% concentration caused highest reduction of mycelial growth of A. solani (44.4, 43.3 and 42.2%, respectively), while O. basilicum at 1 and 5% and N. oleander at 5% caused the lowest inhibition of mycelia growth of the pathogen. In greenhouse experiments the highest reduction of disease severity was achieved by fungicide (Ridomil Plus 50% WP, 15% metalaxy+35% Copper oxychloride, at 2 g L-1) 82.8% followed by the extracts of A. sativum at 5% and D. stramonium at 1 and 5% concentration. The greatest reduction of disease severity was achieved by Ridomil Plus 74.2% followed by A. sativum at 5% and the smallest reduction was obtained when tomato plant was treated with O. basilicum at 1 and 5% (46.1 and 45.2%, respectively). Fungicide, D. stramonium and A. sativum at 5% increased the fruit yield 85.7, 76.2 and 66.7% compared to infected control. All treatments, plant extracts and fungicide (Ridomil Plus), significantly reduced the early blight disease as well as increased the yield of tomato compared to infected control under field condition.

Services
Related Articles in ASCI
Similar Articles in this Journal
Search in Google Scholar
View Citation
Report Citation

 
  How to cite this article:

Nashwa M.A. Sallam , 2011. Control of Tomato Early Blight Disease by Certain Aqueous Plant Extracts. Plant Pathology Journal, 10: 187-191.

DOI: 10.3923/ppj.2011.187.191

URL: https://scialert.net/abstract/?doi=ppj.2011.187.191
 
Received: July 30, 2011; Accepted: October 23, 2011; Published: December 12, 2011



INTRODUCTION

Under Egyptian conditions tomato plants are vulnerable to infection early blight disease caused by Alternaria solani (Ellis and Martin) Sorauer (Abada et al., 2008) which causes great reduction in the quantity and quality of fruit yield. The Alternaria fungus can cause disease on all parts of the plant (leaf blight, stem collar rot and fruit lesions) and result in severe damage during all stages of plant development (Abada et al., 2008).

This disease is controlled mainly with agro chemicals. However, the world wide trend towards environmentally-safe methods of plant disease control in sustainable agriculture calls for reducing the use of these synthetic chemical fungicides. In an attempt to modify this condition some alternative methods of control have been adopted. Recent efforts have focused on developing environmentally safe, long lasting and effective biocontrol methods for the management of plant diseases. Natural plant products are important sources of new agrochemicals for the control of plant diseases (Kagale et al., 2004). Furthermore, biocides of plant origin are non-phytotoxic, systemic and easily biodegradable (Qasem and Aau-Blan, 1996). It is now known that various natural plant products can reduce populations of foliar pathogens and control disease development and then these plant extracts have potential as environmentally safe alternatives and as components in integrated pest management programs (Bowers and Locke, 2004). A number of plant species have been reported to possess natural substances that are toxic to several plant pathogenic fungi (Goussous et al., 2010). Dushyent and Bohra (1997) studied the effect of 11 different plant extracts on mycelial growth of A. solani and found that leaf extracts of some plants i.e. Tamarix aphylla and Salsola baryosma totally inhibited the growth of the pathogen in vivo. Also, Wszelaki and Miller (2005) reported that garlic extracts significantly reduced the early blight disease on tomato. Additionally, several plant extracts have shown antimicrobial activity against fungal pathogens under in vitro and in vivo conditions (Kagale et al., 2004). Therefore, our present study investigated the efficacy of various Egyptian plants leaf extracts, Ocimum basilicum, Azadirachta indica, Eucalyptus chamadulonsis, Datura stramonium, Nerium oleander and Allium sativum for control of early blight of tomato under greenhouse and field conditions. The treatments were compared with a commonly used fungicide (Ridomil Plus).

MATERIALS AND METHODS

Plant materials: Seeds of tomato (Solanum lycopericum L.) cultivar Super Strain B were obtained from the Ministry of Agriculture, Egypt and used in this study. Seeds were sown in plastic pots, each of 30 cm diameter and containing a soil mixture consisting of sand 3 kg pot and 10 g slow-release fertilizer per kg (N.P.K 12: 4: 6). All pots were placed on a benchtop in a climate controlled greenhouse at 30±5°C with 68-80% RH and watered as required.

Isolation and pathogenicity tests of the causal pathogen: Six fungal isolates were isolated from naturally diseased tomato leaves and fruits showing blight symptoms. Pathogenicity tests of Alternaria sp. isolates were carried out under greenhouse conditions in 2007-2008 experiments in greenhouse of Plant Pathology Department, Faculty of Agriculture, Assiut University, Assiut, Egypt. The inoculum was prepared by growing each of the tested isolates on PDA medium at 27°C for 15 days. Then 10 mL of sterile distilled water was added to each plate and colonies were carefully scraped with a sterile needle. The resulting conidial suspension from each isolate was adjusted to 5x106 spores mL-1 and used for inoculation of 20 tomato plants (cv. Super Strain B), using an atomizer. After inoculation, plants were covered with polyethylene bags for 48 h to maintain a high humidity conditions. After 48 h, bags were removed and plants were kept under greenhouse conditions. Pots were maintained in completely randomized design under glasshouse conditions. Two weeks after inoculation, disease severity was recorded. The trial was repeated twice. The intensity of disease was recorded in each treatment following the score chart 0-9 scale (0-Healthy; 1 = 1 to 5%; 2 = 6 to 10%; 3 = 11 to 25%; 5 = 26 to 50% and 7 = 51-75% 9 = >76% leaf area infected) proposed by Latha et al. (2009).

Preparation of extracts: Extracts from leaves of six plants namely, O. basilicum, A. indica, E. chamadulonsis, D. stramonium, N. oleander and A. sativum were collected from different parts of Assiut, Egypt and tested for their efficacy in reducing the mycelial growth of A. solani in vitro using the poisoned food technique (Schmitz, 1930). Ten grams of fresh leaf material of each plant species was collected, washed with water and crushed in a mortar and pestle by adding sterile distilled water at the rate of 10 mL g-1 of plant tissue and the homogenates were centrifuged at 10000xg for 15 min at 4°C and the supernatant solutions were collected. The plant extract was diluted further to have 1 and 5% concentration (v/v). These fractions were sterilized using 0.2 m disposable syringe filters and used for assay of antimicrobial activity as described below.

The PDA media amended with five milliliters of aqueous leaf extract, 1 and 5%, of each plant extracts individually were inoculated with mycelial discs (9 mm diameter) taken from the advancing edges of 7 day-old pure cultures of A. solani. The control experiments had distilled water instead of plant extracts. The inoculated media were incubated at temperature 27±1°C. Four plates were each treatment was used as a replicates. The diameter of the fungal colony was measured using a meter rule along two diagonal lines drawn on the reverse side of each Petri plate 7 days after inoculation. Each treatment was replicated three times with four plates per replication.

Testing of plant extracts against early blight of tomato under greenhouse conditions: Fungicide (Ridomil Plus 50% WP, 15% metalaxyl+35% Copper oxychloride, at 2 g L-1) and plant extracts treatments at 1 and 5% were applied as foliar application, 30 mL on tomato plants, seven week olds and every 15 days up to 60 days of planting after two days from second spraying tomato plants were inoculated with 20 mL of A. solani suspension containing 5x106 cfu mL-1. After inoculation, plants were kept in a climate chamber with 28°C day temperature and 85% relative humidity. Disease development was recorded 15 days after inoculation. Disease severity was recorded as described before. Greenhouse experiments were repeated twice.

Testing of plant extracts on early blight of tomato under field conditions: The field trials were conducted at the Experimental Farm of Faculty of Agriculture, Assiut University, Assiut, Egypt in 2008 and 2009 growing seasons. Field plots (3x3.5 m) comprised two rows and 5 plants/row arranged in a completely randomized block design. Three plots were used as replicates for each treatment as well as for the untreated control treatment. Application of plant extracts was carried out as in greenhouse experiments. Disease development was recorded 15 days after inoculation. Disease severity was recorded as described before. Field experiments were repeated twice. At harvest time, the average accumulated yield was calculated for each treatments including untreated control. Ten plants from each replicate were harvested to assess the total yield of each treatment (ton ha-1).

Statistical analysis: All experiments were performed twice. Analyses showed no significant interaction between the two tests run for any of the treatment. Therefore, results from duplicate tests were combined for final analysis. Analyses of variance were carried out using MSTAT-C program version 2.10 (MSTAT-C 1991). Least Significant Difference (LSD) was employed to test for significant difference between treatments at p = 0.05 (Gomez and Gomez, 1984).

RESULTS

Identification of the causal pathogen: Six fungal isolates were obtained from naturally diseased tomato leaves and fruits showing blight symptoms and identified as A. solani, based on the morphological characteristics (Ellis, 1976).

Pathogenicity tests: Results in Fig. 1 indicate that all the tested isolates of A. solani were able to infect tomato plants causing typical early blight symptoms with different degrees of disease severity. Data indicate that isolates 1, 3 and 5 were highly pathogenic and caused the highest disease severity. Isolates 2 and 4 exhibited the lowest disease severity on tomato plants followed by isolate 6. On the basis of this result, isolate 1 was used in the following experiments.

Effect of plant extracts on radial growth of A. solani: Six plant species were selected and evaluated for the antimicrobial activity against A. solani. All the leaf extracts of tested plants at 1 and 5% concentration were effective in inhibiting the radial growth of A. solani, compared to control. The leaf extract of D. stramonium, A. indica and A. sativum at 5% concentration caused highest reduction of mycelial growth of A. solani (44.4, 43.3 and 42.2%, respectively), followed by E. chamadulonsis and D. stramonium at 1% concentration. O. basilicium at 1 and 5% and N. oleander at 1% caused the lowest inhibition of mycelial growth of the pathogen. Overall the Ridomil Plus at 2 g L-1 caused the highest reduction of the pathogen by 77.8% (Table 1).

Effect of plant extracts on early blight incidence of tomato under artificial infection in greenhouse conditions: The different concentrations of six plant extracts, O. basilicum, A. indica, E. chamadulonsis, D. stramonium, N. oleander and A. sativum, significantly reduced the early blight diseases (Table 2). The greatest reduction 82.8% of disease severity was achieved by Ridomil Plus at 2 g L-1. The most effective treatments from plant extracts were A. sativum at 1 and 5% followed by D. stramonium at 1 and 5% concentration. The least reduction of disease severity was achieved by O. basilicum at 1% (35.2%). Other plant extracts treatments were moderately effective.

Effect of some plant extracts on early blight incidence of tomato under field conditions: All treatments, plant extracts and fungicide (Ridomil Plus at 2 g L-1), significantly reduced the early blight disease under field conditions (Table 3).

Fig. 1: Pathogenicity tests of six isolates of Alternaria solani on tomato plants (cv. Super Strain B) under greenhouse conditions. Different letters indicate significant differences among treatments according to least significant difference test (p = 0.05). Means of standard deviation for twenty plants per treatment are shown

Table 1: In vitro effect of six plants extracts on the linear growth of Alternaria solani
A five milliliters of aqueous leaf extracts prepared from each of the plant sample was mixed with 45 mL of PDA medium (1 and 5%). b The percent inhibition of radial growth of A. solani was calculated. Each treatment was replicated three times with four plates per replication. Values in the column followed by the same letter are not significantly different at (p = 0.05)

Table 2: Influence of six plants extracts on early blight disease of tomato plants under greenhouse conditions
The intensity of the disease was recorded in each treatment as proposed by Latha et al. (2009). Values in the column followed by different letters indicate significant differences among treatments according to least significant difference test (p = 0.05)

Table 3: Influence of six plant extracts on early blight disease and yield of tomato under field conditions
Values in the column followed by different letters indicate significant differences among treatments according to least significant difference test (p = 0.05)

The greatest reduction of disease severity at 74.2% was achieved by Ridomil Plus at 2 g L-1 followed by A. sativum at 5% and the least reduction was obtained when tomato plant were treated with O. basilicum at 1 and 5% (46.1 and 45.2 %, respectively). The other treatments were moderately effective.

Effect of treatments on fruit yield: Data in Table 3 indicate that the efficacy of the Ridomil Plus and plant extracts was reflected in the fruit yield produced. Plants sprayed with fungicide, D. stramonium and A. sativum at 5% increased the fruit yield 85.7, 76.2 and 66.7% respectively, compared to nontreated control. In contrast, O. basilicum, A. indica, E. chamadulonsis and N. oleander treatments increased the fruit yield moderately, ranged between 28.6 to 38.1% compared to infected control.

DISCUSSION

Our results indicated that all tested plant extracts, Ocimum basilicum, Azadirachta indica, Eucalyptus chamadulonsis, Datura stramonium, Nerium oleander and Allium sativum and fungicide, Ridomil Plus 50% WP, caused significant reduction in the linear growth of A. solani. This reduction was gradually increased by increasing the concentration of extracts in the growth medium. Ridomil Plus was more effective than the plant extracts. Similar effect of various other plant products effective against Alternaria spp. have been reported by several workers (Latha et al., 2009; Goussous et al., 2010). Vijayan (1989) reported that the bulb extract of A. sativum, leaf extract of Aegle marmelos and flower extract of Catharanthus roseus inhibited the spore germination and mycelial growth of A. solani. The inhibitory effect of the fungicide on the growth of A. solani was reported by many researchers (Patil et al., 2001; Abada et al., 2008). The inhibitory effect of the tested plant extracts may be due to their direct toxic effect to the pathogen as reported by Vijayan (1989). Investigations on mechanisms of disease suppression by plant products have suggested that the active principles present in plant extracts may either act on the pathogen directly (Amadioha, 2000), or induce systemic resistance in host plants resulting in reduction of disease development (Kagale et al., 2004).

The greenhouse and field experiments indicated that foliar spray of tomato plants by plant extracts and fungicide resulted in significant reduction in early blight infection. However, the tested fungicide was more efficient than plant extracts. These results were similar to previous work on the role of plant extracts in fungal disease control. Several authors including Krebs et al. (2006), Curtis et al. (2004) and Latha et al. (2009) reported that plant extracts from 20 non-host plant species caused reduction of early blight disease and suppressed the mycelial growth of A. solani. All tested plant extracts treatments improved the yield of tomato plants compared to infected control.

In conclusion, present study demonstrated that many plant extracts, O. basilicum, A. indica, E. chamadulonsis, D. stramonium, N. oleander and A. sativum, can be used for the bio-control of early blight disease. Thus, this method of control can contribute to minimizing the risks and hazards of toxic fungicides, especially on vegetables produced for fresh consumption. Further research into these extracts will identify the active compounds responsible for their fungicidal activity.

REFERENCES
1:  Abada, K.A., S.H. Mostafa and M.R. Hillal, 2008. Effect of some chemical salts on suppressing the infection by early blight disease of tomato. Egypt. J. Applied Sci., 23: 47-58.
Direct Link  |  

2:  Amadioha, A.C., 2000. Controlling rice blast in vitro and in vivo with extracts of Azadirachta indica. Crop Protect., 19: 287-290.
CrossRef  |  Direct Link  |  

3:  Bowers, J.H. and J.C. Locke, 2004. Effect of formulated plant extracts and oils on population density of Phytophthora nicotianae in soil and control of Phytophthora blight in the greenhouse. Plant Dis., 88: 11-16.
CrossRef  |  Direct Link  |  

4:  Curtis, H., U. Noll, J. Stormann and A.J. Slusarenko, 2004. Broad-spectrum activity of the volatile phytoanticipin allicin in extracts of garlic (Allium sativum L.) against plant pathogenic bacteria, fungi and Oomycetes. Physiol. Mol. Plant Pathol., 65: 79-89.
CrossRef  |  Direct Link  |  

5:  Dushyent, G. and A. Bohra, 1997. Effect of extracts of some halophytes on the growth of Alternaria solani. J. Mycolo. Plant Pathol., 27: 233-233.

6:  Ellis, M.B., 1976. More Dematiaceous Hyphomycetes. 1st Edn., Commonwealth Mycological Inst., Kew, Surrey, UK., Pages: 507.

7:  Gomez, K.A. and K. Gomez, 1984. Statistical Procedure for Agricultural Research. John-Wiley and Sons Inc., New York.

8:  Goussous, S.J., F.M. Abu el-Samen and R.A. Tahhan, 2010. Antifungal activity of several medicinal plants extracts against the early blight pathogen (Alternaria solani). Arch. Phytopathol. Plant Protect., 43: 1745-1757.
CrossRef  |  Direct Link  |  

9:  Kagale, S., T. Marimuthu, B. Thayumanavan, R. Nandakumar and R. Samiyappan, 2004. Antimicrobial activity and induction of systemic resistance in rice by leaf extract of Datura metel against Rhizoctonia solani and Xanthomonas oryzae pv. oryzae. Physiol. Mol. Plant Pathol., 65: 91-100.
CrossRef  |  Direct Link  |  

10:  Krebs, H., B. Dorn and H.R. Forrer, 2006. Control of late blight of potato with medicinal plant suspensions. Agrarforschung, 13: 16-21.
Direct Link  |  

11:  Latha, P., T. Anand, N. Ragupathi, V. Prakasam and R. Samiyappan, 2009. Antimicrobial activity of plant extracts and induction of systemic resistance in tomato plants by mixtures of PGPR strains and Zimmu leaf extract against Alternaria solani. Biol. Control, 50: 85-93.
CrossRef  |  Direct Link  |  

12:  MSTAT-C, 1991. A Software Program for the Design, Management and Analysis of Agronomic Research Experiments. Michigan State University, East Lansing, MI.

13:  Patil, M.J., S.P. Ukey and B.T. Raut, 2001. Evaluation of fungicides and botanicals for the management of early blight (Alternaria solani) of tomato. PKV Res. J., 25: 49-51.

14:  Qasem, J.R. and H.A. Aau-Blan, 1996. Fungicidal activity of some common weed extracts against different plant pathogenic fungi. J. Phytopathol., 144: 157-161.
CrossRef  |  

15:  Schmitz, H., 1930. Poisoned Food Technique. 2nd Edn., Industry of Engineering Chemical, London, USA., pp: 333-361.

16:  Vijayan, M., 1989. Studies on early blight of tomato caused by Alternaria solani (Ellis and Martin) Jones and Grout. M.Sc. Thesis, Tamil Nadu Agricultural University, Coimbatore, India.

17:  Wszelaki, A.L. and S.A. Miller, 2005. Determining the efficacy of disease management products in organically-produced tomatoes. Plant Health Progress. 10.1094/PHP-2005-0713-01-RS

©  2021 Science Alert. All Rights Reserved