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Articles by S. Shahid Shaukat
Total Records ( 9 ) for S. Shahid Shaukat
  Samreen Saeed and S. Shahid Shaukat
  Seed size variation and its effects on germination and seedling growth were examined in seeds collected from a population of Senna occidantalis. Seed size varied from 0.009-0.029 g per seed. Final germination percentage depended on seed size with large seeds having highest germination percentage, but germination velocity was higher for small seeds. Seedlings from large seeds produced longer roots and shoots than those from small seeds and were able to emerge more rapidly. The seed size had a clear effect on survival with seedlings from large seeds having the highest survival.
  S. Shahid Shaukat and G. R. Sarwar
  The deposits of silicon in the leaves of several grasses and sedges have been investigated. Shape and distribution patterns of opal phytoliths were examined in the adaxial surface of leaf blades. Dumb- bell shape was found to be most common, such phytoliths were generally arranged in two or three rows. Rod, sphere and saddle-shaped phytoliths were specific for certain species and this can be used as a diagnostic character to delimit such species.
  S. Shahid Shaukat , Imran Ali Siddiqui , Nasima Imam Ali and M. J. Zaki
  Efficacy of soil amendment with Lantana camara and various concentrations of three phenolics (caffeic acid, p-hydroxybenzoic acid and (p-coumaric acid) were tested against the soil-borne root-infecting fungi (Fusarium solani and Rhizoctonia solani) in unsterilized sandy-loam soil. The potential impact of L. camara amendment on the rhizosphere population of Pseudomonas aeruginosa and consequent biocontrol potential was also evaluated. Powdered L. camara and its aqueous extract caused substantial suppression of F. solani and R. solani infection in mungbean roots. At high concentration of L. camara (1% w/w), population of P. aeruginosa in the rhizosphere declined but not to a degree that could reduce biological control and growth promoting potential of the bacterium. L. camara and P. aeruginosa used together caused greater suppression of the root-infecting fungi as compared to their individual application. P. aeruginosa mixed with L. camara also resulted in enhanced plant growth. Soil application of caffeic acid at the rate of 10-μg/g soil caused complete inhibition in germination of mungbean. With an increase in phenol concentration, plant growth was progressively reduced and root infection caused by F. solani and R. solani was suppressed. Caffeic acid at 5-μg/g soil caused greater suppression of F. solani whereas p -hydroxybenzoic acid at 10 μ g/g resulted in the maximum inhibition of R. solani.
  S. Shahid Shaukat and Imran Ali Siddiqui
  The allelopathic and antifungal potential of the root leachates of Lantana camara L., a tropical weed was evaluated under glasshouse conditions. Soil drench with full strength concentration caused marked suppression of two root-infecting fungi including Fusarium solani and Rhizoctonia solani. Whereas, a high concentration of the root leachate caused marked inhibition of germination and growth of mungbean, a low concentration (1:2 dilution) enhanced plant growth. When soil was added with urea as an extra source of nitrogen (N) to overcome the phytotoxic symptoms, the toxic effect was not alleviated, suggesting that allelopathic effect due to the root leachate of this weed was not associated with N depletion in the soil. When soil was applied with urea, previously amended with root leachate of L. camara, the efficacy in the control of two soil-borne root-infecting fungi was increased.
  Aly Khan , S. Shahid Shaukat and Iftikhar Ahmad
  A survey of nematode communities associated with chilli fields in eight localities of lower Sindh was conducted. In all eight species were recorded viz., Meloidogyne sp. larvae; Helicotylenchus indicus; Pratylenchus penetrans; Tylenchus sp. larvae; Pratylenchus thornei; Tylenchorhynchus annulatus; Psllenchus hilarulus; Hoplolaimus indicus and Aphelenchus avenae. A principal component ordination showed the relationships between localities and the species. Cluster analysis revealed the grouping of the nematode communities. Two main groups could be recognized, a small group having large populations of Meloidogyne sp. larvae and a large group comprising of communities with saprophytic nematodes and parasitic species such as Helicotylenchus indicus, Tylenchorhynchus annulatus and Pratylenchus spp. with variable densities.
  Aly Khan , S. Shahid Shaukat and Iftikhar Ahmad
  The effect of horse and donkey manure and carbofuran on the population densities of three phytonematodes viz., Helicotylenchus indicus, Meloidogyne sp. (larvae) and Merlinius brevidens associated with garlic crop and garlic yield was investigated. Population densities of all three nematode species were markedly reduced by the manures but more prominently by carbofuran. Yield was substantially increased by the manures and the chemical nematicide carbofuran.
  S. Shahid Shaukat , Zamarrud Tajuddin and Imran A. Siddiqui
  The effects of Launaea procumbens (Roxb.) Rammaya and Rajgopal on seed germination and early seedling growth of four test plant species including mustard, bulrush millet, corn and spinach was evaluated under laboratory conditions. Aqueous extract of L. procumbens at different concentrations (25, 50, 75 and 100% stock solution) inhibited germination of three test species in the order: spinach > mustard > corn; germination of millet was not significantly influenced. Root and shoot growth of all four species was substantially reduced by Launaea extract. The growth was reduced in the order: spinach > mustard > corn > millet. When different modes of extract application were tested, it was found that only the soil application of the aqueous extract had a significant retarding effect on wheat growth while shoot spray or root dip treatment had no such effect. Decaying shoot of L. procumbens in sandy-loam at 5, 10 and 20 g/400 g soil caused substantial inhibition of germination and seedling growth of bulrush millet (Pennisetum americanum) at high dosages. Bioassay of the ether extract of L. procumbens exhibited four zones of inhibition at Rf values 0.1-0.2, 0.7-0.8, 0.8- 0.9 and 0.9-1.0 while a promoter was detected between Rf values 0.3-04. A thin-layer chromatography for the phenolics showed the presence of seven phenolic acids including: salicylic acid, vanillic acid, syringic acid, 2-methylresorcinol, gallic acid and two unknowns.
  S. Shahid Shaukat and Imran A. Siddiqui
  Mineral amendments influence the performance of antagonistic microorganism to suppress soil-borne fungal and nematode diseases. Experiments were conducted to evaluate the influence of zinc on the production of nematicidal compound(s) in vitro and root-knot infection by Meloidogyne javanica in tomato. Nutrient rich medium amended with various concentrations (0.25-2.0 mM) markedly improved the nematicidal activity of rhizobia in vitro. Species and even strain-specific differences were observed among bacteria with respect to their response to different zinc concentrations. Efficacy of the 10 different isolates (66.6% of the total isolates) was maximum when growth medium was amended with zinc at 1.5 mM while 4 isolates (26.6% of the total isolates) exhibited optimal performance when exposed to 2.0 mM zinc. In vitro nematicidal activity of only one strain was optimal at 1.0 mM zinc. Soil amendment with zinc in the form of ZnSO4 at 0.9 mg/kg of soil alone or in conjunction with rhizobia caused significant inhibition of root-knot development and enhanced the growth of tomato plants under glasshouse conditions.
  S. Shahid Shaukat , Imran A. Siddiqui , Maria Hamid , Ghazala Habib Khan and Syed Azhar Ali
  During the survey of the cultivated fields in Karachi and neighborhood (Southern Sindh), 3 strains of Rhizobium phaseoli, 1 strain of R. leguminosarum and R. trifolii each, 5 strains of Sinorhizobium meliloti, 2 strains of Bradyrhizobium japonicum and 3 strains of Bradyrhizobium sp. were isolated and identified. The 15 strains of rhizobia tested for their growth under saline media exhibited varying degree of effects to salt concentrations. Most resistant strain was that of S. meliloti MAT1(R9) while least resistant was that of Bradyrhizobium sp. VRM1(R13). All the rhizobial strains caused significant mortality of Meloidogyne incognita, the root-knot nematode juveniles in vitro, though the strains differed markedly in their toxic activity. The rhizobial strains showed significant interaction with NaCl salinity towards M. incognita
 
 
 
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