Art07_Athar.indd Journal of Applied Botany and Food Quality 84, 162 - 168 (2011) Biotechnology and Drug Development Laboratory, Department of Biochemistry, University of Karachi, Karachi, Pakistan Seaweeds as an alternative to chemical pesticides for the management of root diseases of sunflower and tomato Viqar Sultana, Ghulam Nabi Baloch, Jehan Ara, Syed Ehteshamul-Haque, Rajput M. Tariq, Mohammad Athar (Received August 25, 2010) Summary With the rising popularity of organic farming, due to adverse effect of chemicals, the seaweed fertilizer industry is growing rapidly worldwide. Seaweeds act as natural plant growth stimulator and enable the plants to withstand drought, disease or frost. Root diseases of tomato and sunfl ower caused by root rotting fungi, Fusarium spp., Rhizoctonia solani and Macrophomina phaseolina, and root knot nematode, Meloidogyne spp., are the major constraints in tomato and sunfl ower production. In our studies, ethanol and water extracts of several seaweeds showed signifi cant nematicidal activity against Meloidogyne javanica. In this study, effi cacy of three seaweeds Spatoglossum variabile, Melanothamnus afaqhusainii and Halimeda tuna was compared with a fungicide Topsin-M and a nematicide carbofuran both in screen house and under fi eld condition. Seaweed and pesticides showed more or similar suppressive effect on root pathogens of tomato and sunfl ower by reducing fungal root infection and nematode’s galls on roots and nematode’s penetration in roots. However, mixed application of S. variabile with carbofuran caused maximum reduction in nematode’s penetration in roots and produced greater fresh shoot weight, root length and maximum yield of tomato under fi eld condition. Seaweeds offer a non-chemical means of disease control, which would also protect our environment from the use of hazardous chemicals. Introduction Global utilization of seaweed is a multi-billion dollar industry. Research and utilization of marine algae have increased markedly from last several decades (JIMENEZ-ESCRIG and SANCHEZ-MUNIZ, 2000). A number of products based on algae have been developed and applied in many fi elds like foods, pharmaceuticals, cosmetics and nutritional supplements (SMIT, 2004). Much of this is based on farming of edible species or on the production of agar, carrageen and alginate. Perhaps the longest established, most widespread and most proven effective use of seaweed is as a fertilizer (CHAPMAN and CHAPMAN, 1980; HATTORI, 1999). The high fi ber content of seaweed acts as a soil conditioner and assists moisture retention, while the mineral content is a useful fertilizer and source of trace elements (MAT-ATKO, 1992). They also contain bio-control properties and contain many organic compounds and growth regulators such as auxins, gibberellins and precursor of ethylene and betaine which affect plant growth. Seaweed extracts have been reported to increase plant resistance to pests and diseases, plant growth, yield and quality (JOLIVET et al., 1991; MAT-ATKO, 1992; SHYAMALI et al., 1982). Management of soil-borne plant pathogens, including parasitic nematodes, is one of the single greatest challenges facing modern agriculture worldwide. The importance of soil-borne pathogens in modern agriculture systems is made especially clear by the current rush worldwide to fi nd alternatives to methyl bromide for pre-plant treatment of soils used to produce certain high-value crops. Losses caused by plant parasitic nematodes are estimated about US $100 billion annually (SAIFULLAH et al., 2007), whereas fungal pathogens including species of Fusarium, Phytophthora, Rhizoctonia, Pythium, Verticillium and Macrophomina phaseolina caused billions dollar losses each year. Most soilborne pathogens are diffi cult to control by conventional strategies such as the use of resistant cultivars and synthetic fungicides (WELLER et al., 2002). Moreover the effect of synthetic fungicides on the environment and on human health are leading to signifi cant changes in the use of fungicides for the management of plant disease (PERKINS and PATTERSON, 1997). As a consequence there is an increased emphasis on ways to minimize the use of pesticides (MAAS and GALLETTA, 1997). In our previous study, several seaweeds collected from Karachi coast have shown effective control of root rotting fungi like Macrophomina phaseolina, Rhizoctonia solani, Fusarium species and root knot nematode (Meloidogyne spp.,) on various crops (SULTANA et al., 2007; 2008; 2009). In this study, effi cacy of some seaweeds was examined alone or with common pesticides Topsin-M (fungicide) and carbofuran (nematicide) both in screen house and under fi eld condition in suppressing the soilborne diseases and growth of sunfl ower (Helianthus annuus L.) and tomato (Lycopersicon esculentum Mill.). Materials and methods Seaweeds Melanothamnus afaqhusainii, Spatoglossum variabile and Halimeda tuna collected from Buleji Beach, Karachi were used in these experiments individually or with commercial pesticides, Topsin-M (fungicide) and carbofuran (nematicide) to compare the effi cacy of these seaweeds with common commercial pesticides. The experiments were conducted both under screen house and fi eld conditions using sunfl ower and tomato as test plants. Screen house experiment Dry powder of seaweeds was mixed with sandy loam soil (pH 8.1) to give a concentration of 1.0% w/w. The soil was naturally infested with 3-7 sclerotia of Macrophomina phaseolina g-1 of soil as determined by wet sieving and dilution plating (SHEIKH and GHAFFAR, 1975), 2-6% colonization of Rhizoctonia solani on sorghum seeds used as baits (WILHELM, 1955) and 3,000 cfu g-1 of soil (cfu = colony forming units) of a mixed population of Fusarium oxysporum and F. solani as determined by soil dilution (NASH and SNYDER, 1962). One kg of amended soil was transferred to clay pots (12 cm diam.). The pots were watered daily to allow the decomposition of the organic substrate. After three weeks, four equal size seedlings of tomato (Lycopersicon esculentum Mill.) variety Roma, raised in steam sterilized soil were transplanted after root treatment with aqueous suspension of Topsin-M (200 ppm) for 15 minutes, whereas carbofuran (at 0.05 g/kg soil) was applied after nematode inoculation. A set of seaweeds and pesticides separately were also kept for comparison. The pots without seaweeds and /or pesticides served as control. The pots were kept randomized on a screen house bench at 50% WHC (water holding capacity) with four replicates of each treatment (KEEN and RACZKOWSKI, 1921). The seedlings were inoculated with Meloidogyne javanica eggs/ juveniles at 2000 eggs/second stage juveniles per pot after one week Seaweeds as an alternative to chemical pesticides 163 of seedlings establishment. Whereas in case of sunfl ower six seeds were sown in each pots and 20 ml of Topsin-M (200 ppm) suspension was drenched per pots. After one week of germination only four seedlings were kept and excess were removed and inoculated with nematode suspension similar to tomato experiment. To determine the effi cacy of seaweeds and pesticides on the root pathogens and plant growth, plants were uprooted after six weeks of nematode inoculation. Observations were made on plant height, fresh shoot weight, root length and root weight. Nematode infection was determined by counting the numbers of galls per root system (TAYLOR and SASSER, 1978). To determine nematode penetration and infection by root-infecting fungi, roots from each plant were cut into 1-cm long pieces and fi ve pieces of tap roots from each plant were used for assessment of fungal infection. The remaining roots were mixed thoroughly, and 1-gram sub-sample was wrapped in muslin cloth and dipped in boiling 0.25% acid fuchsin stain for 3-5 minutes. Roots were left in the stain to cool, and then washed under tap water to remove excess stain. Roots were transferred to vials containing glycerol and water (1:1 v:v) with a few drops of lactic acid. Roots were macerated in an electric blender for 45 seconds and the resulting suspension was suspended in 50 ml water. Numbers of juveniles and females in fi ve 5 ml sub samples were counted with the aid of dissecting microscope and numbers of nematode/g root were calculated (SIDDIQUI and EHTESHAMUL- HAQUE, 2001). To determine the incidence of fungal infection, 1-cm long root pieces from tap roots (fi ve pieces from each plant) were surface disinfested with 1% Ca (OCl)2 solution and plated onto potato dextrose agar amended with penicillin (100,000 units/l) and streptomycin (0.2 g/l). After incubation for 5 days at 28 oC, colonies of Macrophomina phaseolina, Rhizoctonia solani and species of Fusarium were recorded. The experiment was conducted twice. Data were subjected to analysis of variance (ANOVA) and means were separated using the least signifi cant difference (LSD) according to GOMEZ and GOMEZ, 1984). Field Experiments Dry powder of seaweeds M. afaqhusainii, S. variabile and H. tuna were mixed in sandy loam soil at 70 g per two meter rows and watered 2-3 days interval to allow the organic matters to decompose. The soil had a natural infestation of 6-18 sclerotia/g of soil of Macrophomina phaseolina, 5-12% colonization of Rhizoctonia solani on sorghum seeds used as baits and 2800cfu/gm of soil of mixed population of Fusarium oxysporum and F. solani. After two weeks of seaweed decomposition, three-week-old tomato seedlings of equal size, raised in steam sterilized soil were transplanted in each row at 12 seedlings per row. In another set, Topsin-M (200 ppm) at 200 ml/ 2 meter row and carbofuran (1 g/ 2 m row) were applied in seaweed amended and non-amended soil. After one week of seedling transplantation, each row was inoculated with aqueous suspension of Meloidogyne javanica eggs/juveniles at 4000/ two meter row. Each treatment was replicated four times and plants were watered 2-3 days intervals depending upon requirement of plants. Effect of seaweed and pesticides on soilborne pathogens, growth and yield of tomato were recorded after 10 weeks of nematode inoculation. Effect of seaweeds on root rotting fungi and root knot nematode was determined as described above except addition of data on nematode’s population in soil. Nematode’s population in soil around roots was determined by Baermann funnel method (SCHINDLER, 1961). In case of sunfl ower, 30 seeds were sown in each row and seedlings were inoculated with nematode suspension after one week of germination. Observations were recorded after 6 weeks of nematode inoculation. Results Screen house Experiment Sunfl ower On sunfl ower application of S. variabile alone or H. tuna with Topsin-M or carbofuran caused complete inhibition of Macro- phomina phaseolina infection on sunfl ower roots. Seaweeds alone or with pesticides also signifi cantly reduced Fusarium solani in- fection (Tab. 1). Application of seaweeds with pesticides also caused a suppressive effect on nematode by reducing the nematode’s penetration in roots (Tab. 1). Seaweed soil amendment showed a positive effect on plant growth by enhancing the plant height (Tab. 2). Tab. 1: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the infection of Macrophomina phaseolina, Rhizoctonia solani and Fusarium solani and Meloidogyne javanica on sunfl ower roots under screen house condition. Treatments M. phaseolina R. solani F. solani No.of knots / Juveniles / females / root system g root Infection % Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 for fungi = Treatments = 11.91, Pathogens = 5.92 ns 10.6 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. 2Mean values in rows for fungi showing differences greater than LSD values are signifi cantly different at p< 0.05. 31.2 0 12.5 12.5 0 18.7 0 0 6.2 6.2 12.5 12.5 25 12.5 12.5 31.2 12.5 18.7 6.2 43.7 6.2 43.7 25 12.5 43.7 18.7 12.5 25 18.7 25 6.2 37.5 18.7 12.5 25 37.5 15.5 4.9 10.5 8.7 8.5 3.8 9.8 7.9 7.6 7.4 9.1 7.4 13.2 1.6 4.9 8.2 3.3 4.9 2.7 1.6 3.3 3.3 1.6 1.6 164 V. Sultana, G.N. Baloch, J. Ara, S. Ehteshamul-Haque, R.M. Tariq, M. Athar Tomato Application of seaweeds alone and or with Topsin-M and carbofuran also showed a suppressive effect on root rotting fungi Rhizoctonia solani and Fusarium solani. Halimeda tuna with Topsin-M and S. variabile with carbofuran caused complete suppression of M. phaseolina, R. solani and F. solani on tomato roots (Tab. 3). Seaweeds alone and or with pesticides also caused a suppressive effect on nematode by reducing the number of galls on roots. Application of H. tuna with Topsin-M and carbofuran caused better protection of roots from nematode invasion than applied separately (Tab. 3). Greater plant height and fresh shoot weight was achieved by the mixed application of S. variabile and Topsin-M (Tab. 4). Whereas H. tuna produced maximum root length. Field Experiment Sunfl ower Seaweed alone and/or with pesticides, Topsin-M and carbofuran caused a suppressive effect on root rotting fungi of sunfl ower by reducing the infection of Macrophomina phaseolina, Fusarium solani and Rhizoctoni solani (Tab. 5). Seaweed application alone or with Topsin-M and carbofuran also produced an adverse effect Tab. 2: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the growth of sunfl ower under screen house condition. Treatments Plant height Fresh shoot weight Root length Fresh root weight (cm) (g) (cm) (g) Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 5.11 ns ns 0.391 1Mean values in column showing differences greater than LSD values are signifi cantly different at p < 0.05. ns = non-signifi cant 20.2 23.4 26.3 28.1 27.3 25.9 25.7 28.8 25.0 31.7 27.5 26.2 3.8 2.9 3.5 3.5 4.6 3.2 3.6 3.7 3.6 3.7 4.1 3.3 12.1 12.5 13.1 9.1 12.4 10.1 9.3 8.5 9.7 11.4 12.0 9.9 0.48 0.52 0.69 0.63 1.02 0.74 0.66 0.99 0.51 0.48 0.70 0.68 6.2 6.2 0 6.2 0 0 0 0 0 0 6.2 0 25 6.2 0 6.2 6.2 6.2 0 6.2 6.2 0 6.2 0 37.5 18.7 12.5 12.5 12.5 31.2 0 25 18.7 0 12.5 12.5 71.5 32.9 33.4 28.7 18.5 41.5 21.2 19.1 18.3 30.7 22.3 10.8 398 381 261 389 246 294 149 166 258 297 253 259 Tab. 3: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the infection of Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and Meloidogyne javanica on tomato roots under screen house condition. Treatments M. phaseolina R. solani F. solani No.of knots / Juveniles / females / root system g root Infection % Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 for fungi = Treatments = 8.71, Pathogens = 4.32 42.32 1922 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. 2Mean values in rows for fungi showing differences greater than LSD values are signifi cantly different at p< 0.05. Seaweeds as an alternative to chemical pesticides 165 on root knot disease (Tab. 5). Maximum reduction in nematode’s penetration in roots was achieved by the mixed application of M. afaqhusainii and carbofuran. Maximum fresh shoot weight was produced by S. variabile used alone (Tab. 6). Tomato Seaweed soil amendment, alone or with Topsin-M and carbofuran caused a suppressive effect on root rotting fungi Rhizoctonia solani and Fusarium solani infecting tomato roots. No infection of F. solani was observed where S. variabile and M. afaqhusainii used alone or where M. afaqhusainii used with Topsin-M and H. tuna applied Tab. 4: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the growth of tomato under screen house condition. Treatments Plant height Fresh shoot weight Root length Fresh root weight (cm) (g) (cm) (g) Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M +A Carbofuran +A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 5.011 1.661 7.851 1.821 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. 19.65 17.87 19.67 21.14 26.9 21.47 23.2 24.1 27.7 24.5 22.87 19.12 3.56 3.19 3.41 3.6 5.92 5 5 3.87 6.9 6.75 4.9 3.9 9.65 5.6 18.9 21.1 19.6 6.4 5 5.5 5.2 12.1 5.6 6.2 1.95 1.92 2.05 2.2 4.2 3.4 2.73 2.36 4.4 3.6 2.9 2.3 Tab. 5: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the infection of Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and Meloidogyne javanica on sunfl ower roots under fi eld condition. Treatments M. phaseolina R. solani F. solani No. of knots / Juveniles / Nematodes / root system females / g root 100 g soil Infection % Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 for fungi = Treatments = 11.91, Pathogens = 5.92 30.81 8.81 ns 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. 2Mean values in rows showing differences greater than LSD values are signifi cantly different at p< 0.05. 18.7 0 6.2 0 0 18.7 6.2 0 6.2 6.2 0 0 12.5 6.2 12.5 0 18.7 12.5 12.5 18.7 0 6.2 0 0 12.5 0 0 0 0 25 0 12.5 0 6.2 0 0 59.6 35.2 38.6 12.0 47.8 10.6 27.3 17.7 16.5 27.4 19.2 21.3 14 11.5 7 9 6 7 8 14 10 9 8 4 30.5 20 32 28 20 40 40 16 36 32 20 28 with carbofuran (Tab. 7). Seaweed also showed inhibitory effect on Meloidogyne javanica. Highest reduction in neamtode’s penetration in roots was achieved by the mixed application of S. variabile and carbofuran (Tab. 7). Soil amendment with seaweeds alone or with pesticides caused a positive effect on plant growth by enhancing the plant height, fresh shoot weight, root length and yield. Maximum plant height was achieved where S. variabile was used with Topsin- M, whereas with carbofuran S. variabile produced greater fresh shoot weight and root length. Spatoglossum variabile also produced highest yield (in terms of number and by weight of fruits) of tomato used either with Topsin-M or carbofuran (Tab. 8). 166 V. Sultana, G.N. Baloch, J. Ara, S. Ehteshamul-Haque, R.M. Tariq, M. Athar Discussion Marine biosphere is an untapped reservoir of agrochemically potent compounds. Seaweed has been used as a fertilizer for many years and are the most widely used biostimulant in agriculture manage- ment (HATTORI, 1999). In this study, seaweeds like Spatoglossum variabile, Halimeda tuna, and Melanothamnus afaqhusainii, showed more or less similar suppressive effect on root rotting fungi and root knot nematode to chemical fungicides (Topsin-M) and nematicide (carbofuran). Considerable evidence has been accumulated in recent years to support and identify the benefi ts associated with the use of Tab. 6: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the growth of sunfl ower under fi eld condition. Treatments Plant height Fresh shoot weight Root length Fresh root weight (cm) (g) (cm) (g) Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S.variabile at 1% w/w (B) M. afaqhusanii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 28.11 50.41 ns 11.11 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. ns = non-signifi cant 71.7 101 67.9 58.2 87.7 62.1 72.0 76.3 67.9 71.0 91.1 75.1 48.0 90.8 55.9 58.8 101.1 46.0 58.2 77.3 69.0 37.8 85.7 74.5 10.9 9.4 10.4 13.7 12.4 10.6 14.1 11.6 11.7 10.2 8.9 11.9 10.1 8.5 8.5 8.1 19.7 7.0 20.3 6.3 5.7 7.3 5.5 8.1 6.2 0 6.2 6.2 0 0 12.5 0 6.2 12.5 6.2 0 56.2 6.2 18.7 12.5 12.5 12.5 31.2 12.5 18.7 31.2 6.2 12.5 43.7 12.5 6.2 25 0 0 12.5 0 6.2 18.7 0 6.2 19.7 9.6 13.3 8.6 9.2 16 6.8 11.6 12.3 8.7 12.1 11.2 85.8 59.9 114.8 29.9 63.1 79.7 53.2 71.2 38.1 14.1 46.4 31.3 44.8 21.4 9.9 8.3 8.9 9.9 9.9 9.9 12.4 9.1 4.1 11.6 Tab. 7: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the infection of Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and Meloidogyne javanica on tomato roots under fi eld condition. Treatments M. phaseolina R. solani F. solani No. of knots / Juveniles / females / Nematodes / root system g root 100 g Infection % Infection % Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 for fungi = Treatments = 12.41, Pathogens = 6.22 9.21 54.41 ns 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. 2Mean values in rows showing differences greater than LSD values are signifi cantly different at p< 0.05. seaweed in crop production systems. Seaweed extracts have been reported to increase plant resistance to pests and diseases, plant growth, yield and quality (JOLVET et al, 1991; PARDEE et al.,, 2004; VERKLEIJ, 1992). Application of seaweed to plants can result in decreased levels of nematode attack (ARA et al., 1997; WU et al., 1997; 1998). Seaweeds contain elaborate secondary metabolites that play a signifi cant role in the defense of the host against predators and parasites which offer a potential novel approach to control population of plant parasitic nematodes (PARACER et al., Seaweeds as an alternative to chemical pesticides 167 Tab. 8: Effect of green (Halimeda tuna), brown (Spatoglossum variabile) and red (Melanothamnus afaqhusainii) seaweeds on the growth and yield of tomato under fi eld condition. Treatments Plant height Fresh shoot weight Root length Fresh root weight No. of fruits / Weight of fruits / (cm) (g) (cm) (g) 4 plant 4 plant (g) Control Topsin-M Carbofuran H. tuna at 1% w/w (A) S. variabile at 1% w/w (B) M. afaqhusainii at 1% w/w (C) Topsin-M + A Carbofuran + A Topsin-M + B Carbofuran + B Topsin-M + C Carbofuran + C LSD0.05 7.51 25.61 5.91 ns 9.61 201.21 1Mean values in column showing differences greater than LSD values are signifi cantly different at p< 0.05. ns = non-signifi cant 34.8 42.0 35.4 42.4 39.3 38.8 33.7 39.0 46.4 43.5 43.3 40.1 28.4 33.7 18.7 43.1 22.3 28.4 30.9 56.2 62.4 89.3 43.7 55.6 23.8 24.2 21.5 22.4 25.2 22.3 19.0 27.0 27.0 30.3 29.4 25.6 3.5 4.8 3.9 5.0 9.4 4.9 3.8 7.5 7.5 8.1 6.6 6.2 13.7 20.0 14.7 21.5 22.5 20.5 13.0 23.2 28.0 28.5 22.5 22.5 152.5 308.7 292.5 317.5 407.5 348.7 175 447.5 490 523 412.5 361.2 1987; JACOBS et al., 2003). In a large number of marine algae, antimicrobial activities are attributed to the presence of acrylic acid. Seaweeds contain 1-aminocyclopropane-1-carboxylic acid (ACC), which has antimicrobial activity (NELSON and VAN STANDEN, 1985). Whereas WU et al, (1997) suggested that betains of the brown alga Ascophyllum nodosum caused a reduction of M. javanica and M. incognita infection on tomato. In this study, seaweeds showed more or less similar suppressive effect on root rotting fungi and root knot nematode like chemical pesticides, Topsin-M (fungicides) and carbofuran (nematicide). However, mixed application of S. variabile with carbofuran caused maximum reduction in nematode’s penetration in roots and produced greater fresh shoot weight, root length and maximum yield of tomato under fi eld condition, which is in agreement with our previous study (SULTANA et al., 2009). Acknowledgement Financial support provided by the Pakistan Agricultural Research Council, Islamabad under the Agricultural Linkages Program (ALP) with USA is sincerely acknowledged. 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