Shazia Shafique

Herbicidal effects of extracts and residue incorporation of Datura metel against parthenium weed

The present study was designed to evaluate the herbicidal activity of Datura metel against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5, 10, 15 and 20% w/v (on a fresh weight basis) concentration of D. metel were tested against the germination and seedling growth of parthenium. Both aqueous and methanol extracts markedly suppressed the germination and seedling growth of parthenium. Generally, the effect of shoot extracts was more pronounced than the effect of root extracts. In foliar spray bioassay, aqueous and methanol shoot extracts of 10% w/v (on dry weight bases) concentrations were sprayed on one-week and two-week-old pot-grown parthenium seedlings. Two subsequent sprays were carried out at five day intervals each. Both the aqueous as well as the methanol extracts significantly suppressed shoot length as well as shoot and root biomass of one-week and two-week-old parthenium plants. In residue incorporation bioassay, crushed shoots of D. metel were incorporated in the soil at 1, 2, … 5% w/w. Parthenium seeds were sown one week after residue incorporation and plants were harvested 40 days after sowing. Incorporation of 2–5% residues significantly reduced germination by 47–89%. Residues of 4 and 5% concentration significantly suppressed plant biomass by 90 and 97%, respectively. The present study concludes that root and shoots of D. metel contain herbicidal constituents for the management of parthenium weed.

Cytological and physiological basis for tomato varietal resistance against Alternaria alternata

BACKGROUND Since tomato is an important food component, it is imperative to enhance its yield against the activities of many devastating fungal pathogens such as Alternaria alternata. The exploitation of plant innate resistance by cultivation of resistant varieties is an effective measure in this regard. In the present study, 28 tomato varieties were tested against 32 A. alternata isolates, and representative varieties were further evaluated to determine the extent and basis of their antifungal resistance. RESULTS A significant increase (104.7%) in polyphenols was recorded in the resistant variety Dinaar compared with the susceptible variety Red Tara. Dinaar also exhibited 100% enhancement of alkaloids and terpenoids along with a 30.7% increase in cell wall hemicellulose content. Significant differences were found in physical barriers (cellulose, lignin and pectin) of the representative varieties when stained tissue sections were subjected to colorimetric analysis. Similarly, polyphenol oxidase, peroxidase and phenylalanine ammonia lyase showed increases of 78.37, 114.67 and 125.11% respectively in the resistant variety. Higher expression of glucanase genes was evident from native gel analysis, in which not only the number of isozymes but also the quantity of individual isozymes was significantly increased. CONCLUSION The resistant variety Dinaar had strong antifungal resistance and can therefore be recommended as suitable for cultivation in the agricultural system of Pakistan.

Management of Parthenium hysterophorus (Asteraceae) by Withania somnifera (Solanaceae)

This study was designed to evaluate the herbicidal activity of Withania somnifera (L.) Dunal against the noxious weed parthenium (Parthenium hysterophorus L.). In a laboratory bioassay, the effect of aqueous, methanol and n-hexane shoot and root extracts of 5%, 10%, 15% and 20% w/v concentrations (on a fresh weight basis) of W. somnifera were tested against the germination and seedling growth of parthenium. In general, aqueous and methanol extracts markedly suppressed the germination, root and shoot growth of parthenium. The shoot extracts were more inhibitory than the root extracts. In a foliar spray bioassay, the aqueous and methanol shoot extracts of 10% w/v (on a dry weight basis) concentration were sprayed on 1-week and 2-week-old pot-grown parthenium seedlings. Two subsequent sprays were carried out 5 and 10 days after the first spray. The aqueous and methanol extracts significantly reduced the length and biomass of parthenium shoots. In a soil amendment bioassay, the crushed shoots of W. somnifera were incorporated in the soil at 1–5% w/w. Parthenium seeds were sown one week after the residue incorporation and plants were harvested 40 days after sowing. All the soil amendment treatments significantly reduced seed germination by 43–89%. The highest dosages of 4% and 5% significantly suppressed the root and shoot biomasses of parthenium. This study concludes that foliar spray of aqueous and methanol extracts, and soil amendment with leaf residue of W. somnifera, can control the germination and growth of parthenium, one of the worlds worst weeds.

Hypersensitive response - A biophysical phenomenon of producers.

Hypersensitive response/reaction is a form of the cellular demise frequently linked alongside plant resistance against pathogen infection. Main transducers for this reaction are the intermediates of reactive oxygen and ion fluxes which are plausibly needed for hypersensitive response (Hpr Sen Rsp). An immediate and enormous energy production and its intra-cellular biochemical conduction are imperative for an Hpr Sen Rsp to be occurred. A number of studies proved that there are such diverse types of factors involved in triggering of Hpr Sen Rsp that morphologies of dead cells have become a vast topic of study. Hpr Sen Rsp could play a frolic role in plants as certain programmed cellular disintegrations in other organisms, to restrict pathogen growth. In fact, Hpr Sen Rsp can be involved in all types of tissues and most of the developmental stages.

Herbicidal activity of flavonoids of mango leaves against Parthenium hysterophorus L.

This study was undertaken to investigate the herbicidal activity of mango (Mangifera indica L.) leaves against parthenium weed (Parthenium hysterophorus L.). The aqueous leaf extract at 15% concentration (on fresh weight basis) significantly reduced germination, shoot length and the shoot and root biomasses of parthenium seedlings. In a leaf residue incorporation pot trial, 2% residue incorporation treatment significantly suppressed the root and shoot biomasses of parthenium, while a 5% residue treatment completely stopped the growth of the weed. Five flavonoids, namely (−)-epicatechin-3-O-β-glucopyranoside (1), 5-hydroxy-3-(4-hydroxyphenyl)pyrano[3,2-g]chromene-4(8H)-one (2), 6-(p-hydroxybenzyl)taxifolin-7-O-β-D-glucoside (tricuspid) (3), quercetin-3-O-α-glucopyranosyl-(1 → 2)-β-D-glucopyranoside (4) and (−)-epicatechin(2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H chromene-3,5,7-triol (5) were isolated from mango leaves. In a laboratory bioassay, 50 ppm solution of compounds 3 and 4 caused yellowing of the parthenium seedlings. A 250 ppm solution of compound 4 also significantly reduced germination and the root and shoot lengths of parthenium seedlings. This study concludes that compound 4 exhibits herbicidal activity against parthenium weed.

Herbicidal activity of Withania somnifera against Phalaris minor

Herbicidal activity of Withania somnifera (L.) Dunal. was studied against Phalaris minor Retz., one of the most problematic weeds of wheat in Pakistan. In laboratory bioassays the aqueous, methanol and n-hexane extracts of 5, 10 and 15% w/v (fresh weight basis) of the roots and shoots of W. somnifera were applied. Extracts in the different solvents exhibited markedly variable herbicidal activities against germination and seedling growth of the target weed species. The methanol extracts showed the highest toxicity. Different concentrations of methanol shoot and root extracts declined the germination of P. minor by 21–71%, its shoot length by 40–72%, its root length by 50–99% and the plant biomass by 32–83%. The aqueous extracts proved to be comparatively less toxic than the methanol extracts, where generally the highest concentration of 15% exhibited pronounced toxicity against the target weed species. There was up to 48, 51, 99 and 55% suppression of the weeds germination, shoot length, root length and plant biomass, respectively, due to the 15% aqueous root and shoot extracts. Generally, the n-hexane extracts of both roots and shoots exhibited insignificant or stimulatory effects against weed shoot length and plant biomass. In a foliar spray bioassay, aqueous and methanol shoot extracts of 10% w/v (dry weight basis) concentration were sprayed on one- and two-week old pot grown P. minor seedlings. Two subsequent sprays were carried out at five day intervals each. The aqueous extract significantly reduced the shoot and root dry biomass of one-week old P. minor plants. In a residue incorporation bioassay, crushed shoots of W. somnifera were incorporated in the soil at 1, 2, … 5% w/w. Phalaris minor seeds were sown one week after residue incorporation and plants were harvested 45 days after sowing. The lower concentrations of 2 and 3% significantly reduced, while higher concentrations of 4 and 5% of residue incorporation completely arrested, the germination of P. minor. The present study concludes that both roots and shoots of W. somnifera contain herbicidal constituents against P. minor.

Mutagenesis and genetic characterisation of amylolytic Aspergillus niger

Aspergillus niger FCBP-198 was genetically modified for its ability to reveal extra cellular α-amylase enzyme activity. From 76 efficient mutants isolated after ultraviolet (UV) irradiation, An-UV-5.6 was selected as the most efficient UV mutant, with 76.41 units mL−1 of α-amylase activity compared to wild (34.45 units mL−1). In case of ethyl methane sulphonate (EMS), among 242 survivors, 74 were assayed quantitatively and An-Ch-4.7 was found to be the most competent, as it exhibited a three-fold increase in α-amylase activity (89.38 units mL−1) than the parental strain. Genetic relationships of the mutants of A. niger FCBP-198 were analysed with a randomly amplified polymorphic DNA–polymerase chain reaction (RAPD–PCR). Results obtained from the comparison between genotypes of A. niger FCBP-198 showed differences in the sizes and numbers of amplified fragments per primer for each isolate. The dendrogram showed that genotypes An-Ch-4.7 and An-Ch-4.2 were distinctly classified into one category, while the isolates An-UV-5.6, An-UV-5.1 and A. niger FCBP-198 have the nearest genetic relationship. The five isolates from A. niger FCBP-198 genotypes shared an average of 65% bands.

Kinetic study of partially purified cellulase enzyme produced by Trichoderma viride FCBP-142 and its hyperactive mutants.

Cellulases are the enzymes that cleave β-1,4 linkages of cellulose, and carbohydrate that is main part of plants’ cell walls. Presently, cellulase isolation and partial purification was executed through ammonium sulfate precipitation. The isolated protein of parental and derived mutants conferred molecular weights of 30, 45 and 55 kDa. The optimum temperature for maximal cellulase activity was 50°C with Ea for substrate hydrolysis of 77.73, 83.97 and 83.14 kJ mol−1 and temperature quotient of 1.0020, 1.0022 and 1.0022 by Trichoderma viride FCBP-142, Tv-UV-5.6 and Tv-Ch-4.3, respectively. The enzyme was stable at 50°C for about 60 min but rapid denaturation occurred above 55°C. The enzyme showed optimum activity at pH 4.0 and involved two types of acidic and basic limbs with pKa1 and pKa2. The pKa1 of active site presented a significant shift from 2.55 to 2.9 and 3.1 by Tv-UV-5.6 and Tv-Ch-4.3, respectively in comparison to parental strain. Likewise, pKa2 moved from 6.05 to 6.5 and 6.4. Enzyme kinetics displayed Michaelis-Menten constant Km 0.6, 0.5 and 0.28 mg mL−1 and Vmax value of 8.33, 10 and 9.09 Units mL−1 for parental, Tv-UV-5.6 and Tv-Ch-4.3, respectively.

Alpha-amylase production by toxigenic fungi

This study is concerned with the screening of Alternaria alternata (Fr.) Keissler and Alternaria tenuissima (Kunze ex Pers.) Wilts strains for the biosynthesis of α-amylases. Nine strains of A. alternata and three strains of A. tenuissima were grown on enzyme production medium (EPM) and potato dextrose agar (PDA) using three pH levels (4.5–6.5); then the selected strains, able to produce bigger zones of starch hydrolysis on solid media, were subjected the testing of their amylolytic efficacy in liquid medium. In primary screening, the amylolytic activity of all the strains was tolerant to a wide range of initial culture pH values (4.5–6.5). Of all the cultures tested, A. alternata strains FCBP-100 and FCBP-385, and A. tenuissima strains FCBP-183 and FCBP-252 exhibited the maximum potential in terms of starch hydrolysis at pH 4.5 on EPM, and hence were selected for further studies. In secondary screening, the optimum pH of fermentation medium was adjusted to 4.5 using 0.05 M citrate buffer for the estimation of amylolytic enzyme activities. At 48 h incubation, the maximum α-amylase activity (31.8 units mL−1) was discerned by A. tenuissima strain FCBP-252.

Molecular characterisation of UV and chemically induced mutants of Trichoderma reesei FCBP-364

Cellulases are a highly diverse group of enzymes whose function is crucial to the healthy functioning of the biosphere, since more than half of all biomass on the planet consists of their substrate, cellulose. Trials were conducted to study the effect of mutagenesis by ultraviolet (UV) irradiation (5–40 min) and ethyl methane sulphonate (EMS) treatment (50–300 µg mL−1) to obtain hyperactive cellulase enzyme producers. Putative mutants of Trichoderma reesei FCBP-364 were selected on the basis of their bigger hydrolysing zone formation and compared to the parental strains quantitatively. UV- and EMS-treated putative mutants of the test strains exhibited a 1.5–2-fold enhancement in enzymatic activity over the parental strain. The profile of genetic variability among native and mutant derivatives was scrutinised through random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR). The scanned amplicons confirmed the modification in genetic make up which might be the cause of the stir up in the enzyme activity.