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Articles by S. Shahid Shaukat
Total Records ( 17 ) for S. Shahid Shaukat
  Zarina B. and S. Shahid Shaukat
  Surveys of various crop fields and lawns of Karachi and its vicinity were conducted to record new hosts of root-knot nematode (Meloidogyne spp.). Five plant species were reported as new hosts of root-knot nematode Meloidogyne incognita and M. javanica for the first time from Pakistan.
  Rashida Perveen , S. Shahid Shaukat and Iftikhar Imam Naqvi
  The effect of atrazine on the levels of carbohydrates, amino acids, potassium, phosphate and sodium contents in shoots and roots of bean plant were investigated. Application of atrazine amounting, 10 to 100 ppm resulted in decrease in carbohydrate, potassium, phosphate and sodium contents of roots and shoots of bean plants. However, amino acid content was reduced in shoot as compared to root wherein it got enhanced at 10 to 100 ppm atrazine concentration. A little growth stimulant effect was observed at 5 ppm concentration of atrazine in shoots and roots of bean plants.
  S. Shahid Shaukat , Nadia Munir and Imran A. Siddiqui
  The effects of Conyza canadensis (L.) Cronquist on seed germination and early seedling growth of six test plants namely tomato, radish, wheat, corn, millet and mungbean was investigated. Aqueous extract of C. canadensis at different concentrations (25, 50, 75 and 100% stock solution) inhibited the germination, root and shoot growth of all the six test species. Germination was reduced by the shoot extract in the order: tomato > radish > millet = corn > mungbean > wheat. Both root and shoot growth of the test species were reduced to varying degree and shoot growth was usually affected to a greater degree than the root growth, particularly in tomato. Decaying shoot of C. canadensis in sandy-loam at 5, 10 and 20 g/ 400 g soil substantially inhibited germination and seedling growth of bulrush millet (Pennisetum americanum) at all the dosages and no germination occurred at the highest dosage (20 g/400 g soil). Bioassay of the ether extract of C. canadensis disclosed two significant zones of inhibition at Rf values of 0.2-0.3 3 and 0.7-0.8. Chromatography for the phenolics revealed the presence of four phenolic compounds: gallic acid, vanillic acid, catechol and syringic acid.
  S. Shahid Shaukat , Mohammad Mushtaq and Zamin Shaheed Siddiqui
  The effect of heavy metals including lead, chromium and cadmium on germination, seedling growth, dry biomass accumulation and phenolic contents of two species viz. Pennisetum americanum and Parkinsonia aculeata were studied. Chromium and cadmium were applied as chloride while lead was used both as nitrate and chloride. Final germination percentage was greatly reduced by cadmium, chromium and lead salts in both the test species at concentrations of 50 ppm or more. Germination reduction was markedly higher in Pennisetum americanum compared to Parkinsonia aculeata treated with cadmium and chromium. Lead chloride inhibited germination more severely than did lead nitrate. Both root and shoot growth were also reduced significantly by Cd, Cr and PbCl2. In both the species root growth was inhibited to a greater extent than shoot growth. Phenolic contents were substantially elevated in both the test species following treatment with heavy metals particularly at higher concentrations (200 and 400 ppm). Parkinsonia aculeata was less affected in terms of germination, root and shoot growth and dry matter accumulation as compared to Pennisetum americanum, exhibiting some degree of tolerance to heavy metals.
  Nazia Burhan and S. Shahid Shaukat
  The phytotoxicity of atrazine and three phenolic compounds (i.e., benzoic, p-coumaric and caffeic acids) was investigated. The germination of six test species was reduced by atrazine in the order: pearl-millet > wheat> turnip> carrot> corn> mustard. Whereas, the phenolic compounds affected the germination of pearl-millet in the order: caffeic acid> benzoic acid> p-coumaric acid. Atrazine in conjunction with the three phenolic compounds exhibited synergistic effect on the process of germination and seedling growth.
  Zenab Rebaz , S. Shahid Shaukat and Imran A. Siddiqui
  Effect of Anagallis arvensis L. on seed germination and early seedling growth of six test species was examined. Aqueous extract of A. arvensis inhibited germination, root and shoot growth of all the six test species. The species exhibited differential response to the extract. Germination was reduced by the shoot extract in the order: pearl millet > mustard > carrot > turnip > wheat = corn. Decaying A. arvensis in sandly-loam soil at 5, 10 and 20 g / kg soil substantially inhibited germination and seedling growth of pearl millet at all the dosages. Bioassay of the extract of A. arvensis revealed two zones of inhibition at Rf values 0.8-0.9 and 0.9-1.0. Chromatography for the phenolics revealed the presence of three phenolic acids: salicylic acid, cinnamic acid and caffeic acid.
  Nazia Burhan , S. Shahid Shaukat and Asmat Tahira
  The effects of heavy metals cobalt and zinc on germination, seedling growth, and dry biomass accumulation of two species viz., Pennisetum americanum and Parkinsonia aculeata were investigated. Cobalt and zinc were used as nitrate and chloride. Final germination was reduced greatly at higher concentrations. Germination reduction was markedly higher in Pennisetum compared to Parkinsonia. Reduction in root growth was relatively greater than the shoot growth. Parkinsonia exhibited some degree of tolerance against heavy metals in terms of germination, root and shoot growth and dry biomass accumulation. The mechanisms of tolerance and co-tolerance to heavy metals are discussed.
  Imran A. Siddiqui , Amer-Zareen , M. Javed Zaki and S. Shahid Shaukat
  The efficacy of Trichoderma viride, T. harzianum, T. hamatum, T. koningii and T. pseudokoningii was tested for the control of Meloidogyne javanica, root knot nematode in okra and mungbean. Culture filtrates of Trichoderma spp., significantly reduced egg hatching and showed nematicidal activity by killing second stage juveniles of M. javanica. Soil application with conidial suspension of T. harzianum significantly reduced nematode population densities and root knot development in okra and mungbean. Apart from suppressing root knot nematode, T. harzianum also elevated plant height and fresh shoot weight of both okra and munhbean.
  Imran Ali Siddiqui , Amer-Zareen , S. Shahid Shaukat and M. Javed Zaki
  Efficacy of different species of rhizobia including, Rhizobium trifolii, R. phaseoli, R. meliloti, Bradyrhizobium japonicum and Bradyrhizobium sp., were tested in the control of Meloidogyne javanica, the root-knot nematode on Vigna mungo under laboratory, greenhouse and field conditions. Cell-free culture filtrates of the rhizobium species significantly reduced egg hatching and caused mortality of M. javanica larvae In vitro. In pot experiments and under field conditions, Bradyrhizobium sp., gave better biocontrol along with enhanced plant growth and nodulation.
  S. Shahid Shaukat and Imran Ali Siddiqui
  Aqueous extract of six weed species including Argemone mexicana, Sonchus asper, Abutilon indicum, Xanthium strumarium, Solanum nigrum and Mavastrum coromandelianum were tested for their activity towards egg hatching and juvenile mortality of Meloidogyne javanica, the root-knot nematode. Aqueous extract of A. mexicana was most lethal to M. javanica juveniles and caused significant inhibition in egg hatching. In general, with an increase in extract concentration and duration for which the juveniles were exposed, mortality increased markedly. Results demonstrated that A. mexicana could be exploited for the suppression of root-knot disease in crops.
  Zamarrud Tajuddin , S. Shahid Shaukat and Imran A. Siddiqui
  Effect of Solanum forskalii Dunal on seed germination and early seedling growth of three test plants namely mustard, wheat and corn was examined. Aqueous extract of S. forskalii at different concentrations (25, 50, 75 and 100% stock solution) inhibited the germination, root and shoot growth of all the three test species. Germination and growth were reduced by the shoot extract in the order: mustard > corn > wheat. Decaying shoot of S. forskalii in sandy loam at 5, 10 and 20 g/kg soil substantially inhibited germination and seedling growth of bulrush millet (Pennisetum americanum) at all the dosages. Bioassay of the ether extract of S. forskalii revealed four zones of inhibition at Rf values 0.1-0.2,0.2-0.3, 0.8- 0.9 and 0.9-1.0. Chromatography for the phenolics revealed the presence of nine phenolic compounds: salicylic acid, vanillic acid, syringic acid, catechol, gentisic acid, 4-methylresorcinol, protocatechuic acid, pyrogallol and an unknown.
  Sofia Alvi , Rashida Perveen , Iftikhar Imam Naqvi and S. Shahid Shaukat
  Effect of atrazine was determined on the absorption and accumulation of phosphorous (P32 ) in bean plants and results have been explained in relation to other physiological processes. Atrazine seemed to be highly toxic to the seedlings at all concentrations used. The injury caused by the herbicide increased with its concentration. It was found to decrease the contents of chlorophyll a, chlorophyll b and carbohydrates, which reflects its effectiveness as a photosynthetic inhibitor. Potassium and protein contents were decreased significantly at 10 to 100 ppm atrazine. The uptake of phosphorus was also recorded and it declined with time. The accumulation of P32 was inhibited at 10 to100 ppm concentrations of atrazine. Some growth stimulating effects were also observed at 5 ppm level.
  M. Sardar Alam , S. Shahid Shaukat , Mubarik Ahmed , Shamim Iqbal and Akhlaq Ahmad
  Wheat and rice godowns in Pakistan have three to twelve years history of phosphine fumigation. Coleopterous adults and larvae from these godowns were collected, cultured and tested for phosphine resistance. Strains of Tribolium castaneum Hbst., Rhizopertha dominica F. and Trogoderma granarium Everts., exhibited varied levels of resistance, whereas all four strains of Sitophilus oryzae L. showed marginal resistance over the susceptible strain. Certain strains of R. dominica and T. castaneum were found to have 80-fold resistance. The possible causes of resistance and the methods of their control are discussed.
  Rashida Perveen , Irfan Wahid , Iftikhar Imam Naqvi and S. Shahid Shaukat
  The study deals with a series of experiments to investigate absorption of radioactive phosphate from different parts of young Triticum aestivum L. (wheat variety Sutlej-86) plants. Considerable transport of P32 occurred when the labelled phosphate was fed through roots. The plants showed considerable variation in the rate of absorption and translocation of P32 with respect to time. Absorption through leaves was found at a lower level compared to roots. Downward movement of P32 was minimal. Therefore it can be concluded that only root has the capability to provide feeding route for plant.
  Amer Zareen , M. Javed Zaki , S. Shahid Shaukat and S. R. Gowen
  Pasteuria spore attachment to root knot juveniles reduced significantly (p<0.001), as dilution factor of bacterial suspension was increased. Isolate UK 1 provided maximum spore attachment to Meloidogyne juveniles in all three dilutions of bacterial spore suspension (S, S/2 and S/4) compared to other test isolates and control. Infected juveniles by spores of all bacterial isolates (UK 1, PK 1 and PK 2) significantly (p<0.05) suppressed invasion to tomato roots. There was significant difference (p<0.001) in root invasion by nematodes exposed to the different concentrations of test bacterial isolates. Temperatures i.e. 15 and 35°C exhibited reduction in bacterial spore attachment to the root knot juveniles. Whereas 25 and 30°C favored bacterial infection of nematodes.
  Zarina Begum , S. Shahid Shaukat and Imran A. Siddiqui
  Aqueous shoot extract of four weed species including Conyza canadensis, Blumea obliqua, Amaranthus viridis and Eclipta prostrata inhibited egg hatch and caused mortality of Meloidogyne javanica, the root-knot nematode juveniles in vitro to varying extent with A. viridis being the most effective. The efficacy of the powdered shoot material as soil organic amendment was tested against two nematode inoculum levels (2000 and 4000 J2 pot G 1) in a pot experiment. Soil amendment with the powdered shoot material generally reduced nematode population density, root-knot development and reproductive potential of M. javanica in brinjal roots. A. viridis was most effective in the suppression of root-knot nematode at both the nematode inoculum rates but caused slightly reduction in plant growth presumably owing to its allelopathic activity in soil.
  S. Shahid Shaukat , Imran A. Siddiqui and Nasima Imam Ali
  Powdered shoot extract of Launaea procumbens, a tropical ruderal and agrestal weed, inhibited egg hatch and caused mortality of Meloidogyne javanica juveniles in vitro. However, ethanol extract of L. procumbens did not inhibit radial growth of root-infecting fungi including Macrophomina phaseolina, Fusarium solani and Rhizoctonia solani in vitro. Soil amendment with powdered shoot of L. procumbens markedly reduced root-knot infection caused by M. javanica in mungbean. Population densities of M. javanica were significantly lower in soil amended with 5.0% L. procumbens while a 2.5% amendment did not produce significant reduction in the nematode populations in soil. Whereas low dosage (2.5%) of L. procumbens significantly enhanced plant growth, high dosage (5%) reduced fresh shoot and root weights of mungbean indicating allelopathic effect. Soil amendment with L. procumbens resulted in marked changes in fungal community structure and composition. Fungi like Fusarium semitectum and a sterile fungus (red pigmented) were exclusively isolated from L. procumbens amended soils. On the other hand, all the fungal species isolated from L. procumbens amended soils were also present in unamended soils. Soil amendments with L. procumbens also altered fungal community structure in the root tissues of mungbean. Both general diversity and equitability of fungal community at 2.5% L. procumbens increased appreciably over the controls but at 5% dosage substantially decreased compared to controls, substantially though species richness declined at both the dosages. Dominance concentration followed an opposite trend to that of general diversity.
 
 
 
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