Syed Ehteshamul-Haque

Biological control of root rot-root knot disease complex of tomato.

Efficacy of Pseudomonas aeruginosa alone or in combination with Paecilomyces lilacinus was evaluated in the control of root-knot nematode and root-infecting fungi under laboratory and field conditions. Ethyl acetate extract (1 mg/ml) of P. lilacinus and P. aeruginosa,respectively, caused 100 and 64% mortality of Meloidogyne javanica larvae after 24 h. Ethyl acetate fractions of biocontrol agents were more effective than hexane extracts in the suppression of M. javanica larvae, indicating that active nematicidal compounds are intermediary in polarity. In field experiments, biocontrol fungus and bacterium significantly suppressed soilborne root-infecting fungi including Macrophomina phaseolina, Fusarium oxysporum, Fusarium solani, Rhizoctonia solani and Meloidogyne javanica, the root-knot nematode. P. lilacinus parasitized eggs and female of M. javanica and this parasitism was not significantly influenced in the presence of P. aeruginosa. P. aeruginosa was reisolated from the inner root tissues of tomato, whereas P. lilacinusdid not colonize tomato roots.

Suppression of the root rot–root knot disease complex by Pseudomonas aeruginosa in tomato: The influence of inoculum density, nematode populations, moisture and other plant-associated bacteria

The influence of different application rates of the plant growth-promoting rhizobacterium, Pseudomonas aeruginosa, population densities of the root-knot nematode, Meloidogyne javanica, moisture and other plant-associated bacteria in the suppression of root rot–root knot disease complex of tomato are described. The impact of these factors on bacterial rhizosphere and inner root and shoot establishment are also presented. The highest inoculum level of P. aeruginosa (7.4 × 108 cfu ml−1) in the presence of the lowest population density of M. javanica (500 J2/plant) caused the greatest reduction in gall formation due to M. javanica. The number of root–knot nematodes recovered from soil and roots treated with P. aeruginosa were also significantly reduced. Root infection caused by the soilborne root-infecting fungi Fusarium oxysporum, F. solani and Rhizoctonia solani was also effectively suppressed following application of P. aeruginosa. A P. aeruginosa-Bacillus subtilis treatment was the most effective in the suppression of root-rot disease complex with enhancement of plant growth. Biocontrol and growth promoting potential of the bacterium was enhanced when soil was kept at 50% or 75% moisture holding capacity, whereas a 25% MHC reduced bacterial efficacy. Rhizosphere population of P. aeruginosa declined drastically in P. aeruginosa-Bradyrhizobium japonicum treatments. Rhizosphere colonisation by P. aeruginosa seems to be governed by two factors: Initial inoculum size of the bacterium and severity of the root-knot disease. Endoroot and endoshoot colonisation of the bacterium was dependent on degree of root-colonisation by Fusarium oxysporum. An inoculum level 2.5 × 108 cfu/ml of P. aeruginosa was optimal for the enhancement of plant growth, whereas inoculum below this level reduced plant growth.

Cytotoxic activity of marine macro‐algae on Artemia salina (Brine shrimp)

A total of 22 ethanol extracts of seaweed species (13 brown, 6 green and 3 red) collected from the Karachi coast were investigated for brine shrimp cytotoxicity. Of all the species, only six namely Stoechospermum marginatum, Sargassum swartzii, S. binderi, Spatoglossum asperum, Stokeyia indica (brown) and Caulerpa racemosa (green) showed significant activity. n‐Hexane‐soluble fractions of the ethanol extract of S. marginatum and S. swartzii were found to be responsible for the activity, whereas the methanol‐soluble fractions of S. asperum and S. binderi were most active. The water extract of S. indica and C. racemosa exhibited the most prominent activity (LC50 value below 70 µg/mL) when compared with the ethanol extracts and their fractions. Cytotoxic activity may be due to the compounds differing in polarity. Copyright© 1999 John Wiley & Sons, Ltd.

Comparative efficacy of brown, green and red seaweeds in the control of root infecting fungi and okra

The effect of soil amendment by brown, green and red seaweeds was studied in controlling the root rot infecting fungi of okra seedlings in the greenhouse. The soil amendment with seaweeds Stokeyia indica, Padina pavonia (brown), Solieria robusta (red), at 1% w/w redaced Macrophomina phaseolina, Rhizoctonia solani and Fusarium solani infection on okra roots. Codium iyengarii (green) at 0.5 % w/w was effective against F solani, while at 1% w/w was found phytotoxic. S. robusta showed better control of F. solani infection when used with Pseudomonas aeruginosa than either used alone. S. robusta produced better plant height and fresh weight of shoot than P. aeruginosa. Results of the present study suggest that the use of brown seaweeds S. indica and P. pavonia alone and S. robusta alone or in combination with P. aeruginosa have great potential to control root-infecting fungi of okra with enhancement of plant growth. These seaweeds alone or in combination with P. aeruginosa may be utilized as biological control of root infecting fungi of okra.

Suppression of Root Pathogens of Tomato by Rhizobia, Pseudomonas aeruginosa, and Mineral Fertilizers

ABSTRACT Root diseases caused by root-rotting fungi and root-knot nematodes are a serious problem in tomato (Lycopersicon esculentum Mill.) production throughout the world. Due to constraints in use of synthetic pesticides, alternate methods for disease management including biocontrol and cultural practices are being sought out. The effect of rhizobia (Bradyrhizobium japonicum), Pseudomonas aeruginosa, a plant growth–promoting bacterium (PGPR), and mineral fertilizers (urea and potash) was examined in suppressing the root-rotting fungi and root-knot nematodes. Use of P. aeruginosa and B. japonicum alone or with mineral fertilizers significantly reduced infection of tomato roots by the root-rotting fungi Macrophomina phaseolina, Rhizoctonia solani, and Fusarium solani. Application of PGPR and rhizobia with urea or with both urea and potash resulted in greater suppression of M. phaseolina than when either organism was used alone. Use of P. aeruginosa or B. japonicum alone or with mineral fertilizers suppressed the root-knot nematode Meloidogyne javanica by reducing numbers of galls on roots, nematode establishment in roots, and nematode populations in soil. The tallest plants occurred due to treatment with P. aeruginosa combined with potash and urea. The maximum shoot fresh weight occurred when treatment was P. aeruginosa or B. japonicum used with urea and potash or with urea alone. Application of rhizobia or PGPR has a greater potential to suppress tomato root pathogens when used in conjunction with mineral fertilizers then when used alone.

Hypolipidaemic potential of seaweeds in normal, triton-induced and high-fat diet-induced hyperlipidaemic rats

Numerous epidemiological studies have shown that long-term hyperlipidaemia is associated with coronary heart disease. The dietary and pharmacological lowering of elevated plasma LDL cholesterol appears to be one of the methods to reduce the development of atherosclerosis and related heart diseases. During this study, ethanol extracts of 13 seaweed species were tested for hypolipidaemic potential in normal rats, some of these caused positive effect by lowering the total cholesterol, triglyceride and LDL cholesterol with increase in HDL cholesterol. Efficacy of eight seaweeds Dictyota dichotoma var. intrica, Jolyna laminarioides, Melanothamnus afaqhusainii, Sargassum binderi, Sargassum swartzii, Halimeda tuna, Spatoglossum variabile, and Solieria robusta was also examined in triton-induced hyperlipidaemic rats. Three potential seaweeds J. laminarioides, S. binderi and M. afaqhusainii were further evaluated in high-fat diet-induced hyperlipidaemic rats. These seaweeds showed effective hypolipidaemic potential in triton-induced and high-fat diet-induced hyperlipidaemic rat models. Liver and cardiac enzymes like LDH, ALP, ASAT and ALAT were not adversely affected by seaweeds. Hypolipidaemic potential of some of the seaweeds is comparable with common hypolipidaemic drugs such as bezafibrate (Lipocor) and fenofibrate (Fenoget).

Cultivar response against root-infecting fungi and efficacy of Pseudomonas aeruginosa in controlling soybean root rot

Abstract A study was conducted in the greenhouse to examine the resistance of three soybean cultivars against root-infecting fungi, and to determine the role of five strains of Pseudomonas aeruginosa in protecting the roots from these fungal pathogens. In this study soybean cv RAWAL was found to be less susceptible against charcoal rot fungus Macrophomina phaseolina than cvs PARC and BRAGG. Most of the strains of P. aeruginosa used as seed dressing significantly reduced M. phaseolina and Rhizoctonia solani infection on all three cvs PARC, BRAGG and RAWAL (p < 0.05). Most of the strains of P. aeruginosa were effective on cv PARC against Fusarium solani infection, while on cv BRAGG P. aeruginosa strain Pa3, and on cv RAWAL strain Pa5 were effective. Both strains Pa3 and Pa22 gave maximum plant height and fresh weight of shoots, respectively on cvs PARC and BRAGG than other strains. These characteristics make these P. aeruginosa strains good candidates for use as biocontrol agents against soil-borne plant pathogens.