Studies on pesticides based on coumarin. III. Synthesis and antifungal activity of substituted 4-methyl-coumarins and related compounds

A series of substituted 4-methylcoumarins was synthesised and the members tested for their toxicity towards mycelial growth of seven phytopathogenic fungi in culture. Rhizoctonia solani, Alternaria alternata and Fusarium solani exhibited maximum sensitivity to these compounds whereas Pythium aphanidermatum, Colletotrichum falcatum, Drechslera oryzae and Macrophomina phaseolina were relatively less sensitive. 6-Ethyl-3-n- propyl-7-hydroxy4-methylcoumarin ( I ) was relatively toxic towards all fungi except C. falcatum, P. aphanidermatum and M. phaseolina. The 6-n-butyl ( III ) and 6-(1, 1, 3, 3-tetramethylbutyl) ( VI ) derivatives were highly toxic to R. solani with EC₅₀, values of lμg ml^?1.     

Development of an Indirect ELISA for the Detection of Antibodies against Peste-des-petits-ruminants Virus in Small Ruminants

Peste des petits ruminants (PPR) is an acute, febrile, highly contagious and economically important viral disease of small ruminants. A polyclonal antibody based indirect ELISA was developed for detection of antibodies to PPR virus in the serum samples of goats and sheep using purified PPR viral antigen propogated in Vero cell culture. A threshold (cut-off) value was set as twice the mean of the negative population based on the distribution of known negative serum samples in respect of PPR virus antibodies in the test. A total of 1544 serum samples from goats and sheep were screened by indirect ELISA and competitive ELISA. The indirect ELISA compared very well with competitive ELISA, with a high degree of specificity (95.09%) and sensitivity (90.81%). When compared with virus neutralization test, the present assay had 100% specificity and 80% sensitivity. With serum samples, the assay could clearly differentiate animals from the infected population from uninfected ones. These results suggest that the indirect ELISA may be a good alternative tool to competitive ELISA for seroepidemiological surveys.     

Ribotyping of Indian Isolates of <Emphasis Type="Italic">Pasteurella multocida</Emphasis> Based on 16S and 23S rRNA Genes

The applicability of ribotyping based on 16S and 23S rRNA was evaluated for molecular epidemiological studies. Forty-eight isolates of Pasteurella multocida isolated from different hosts and geographical locations and one reference isolate were ribotyped. Only four ribotypes were found. All the isolates including reference isolate from wild carnivores had the same ribotype, though they had different serotypes. The isolate from a tiger had one band in addition to the bands present in the major ribotype. The isolates from lions represented two ribotypes; of these ribotypes, one (r2) had an additional band of 3.6 kbp, which was absent in all other ribotypes. The second ribotype (r4) from a lion had one band missing (6 kbp) that was present in the other ribotypes. These isolates were further typed using ERIC-PCR and REP-PCR. With ERIC-PCR and REP-PCR, higher D values of 0.83 and 0.89 were obtained. The current study revealed that ribotyping is not a very efficient typing tool for use in molecular epidemiology for differentiation of isolates.     

Water and nitrogen interaction on soil profile water extraction and ET in maize-wheat cropping system

In the present study, water and nitrogen interaction on soil profile water extraction and evapo-transpiration (ET) was investigated taking a field experiment on a clay loam soil (Typic Haplustept) at the Indian Agricultural Research Institute, New Delhi with four consecutive crops (maize-wheat-maize-wheat) taken from July 2002 to April 2004. Three levels of water regime, namely W1, W2 and W3 referring to limited, medium and maximum irrigation were applied to each crop depending on the seasonal rainfall and the critical crop growth stage. The three water regimes were used with five nitrogen levels from T1 to T5, (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source) in a split plot design for the four crops grown in sequence.Significant water and nitrogen interaction was observed for ET and soil profile water extraction pattern. Averaged across nitrogen treatments, ET in W2 and W3 were higher by 17 and 26%, respectively than W1 in maize 2002 and by 12 and 19% in maize 2003. In case of wheat, ET in W2 and W3 were higher by 27 and 58% than W1 in 1st crop and by 37 and 70% in 2nd crop. The effect of nitrogen regime, however, was prominent in both crops of maize and wheat, with significantly higher profile soil moisture depletion in T4 of each water regime. In all cases, lowest water depletion was observed in control plots receiving 0% N.In both crops, water extraction from surface 60 cm was highest in W3 followed by W2 and W1. In maize, the % extraction from 0 to 60 cm layer varied from 71 to 76% (W1), 70-79% (W2) and 75-82% (W3), whereas the values for wheat were 70-77, 72-79 and 75-83% for W1, W2 and W3, respectively. The 90-120 cm layer contributed only 3-14% to total water extraction in both the crops. From 90 to 120 cm layer, higher extraction was observed in W1 as compared to W3. The extraction values in W1, W2 and W3 in maize were 9-13, 7-14 and 3-9, respectively, whereas the corresponding values in wheat were 8-14, 5-12 and 3-7% for the three water regimes. Effect of nitrogen treatments on water extraction from deeper layer was observed with higher extraction in highest fertilized treatment (T4) as compared to other treatments.     

Comparative study of conventional and artificial neural network-based ETo estimation models

Accurate estimation of reference crop evapotranspiration (ETo) is required for several hydrological studies and thus, in the past, a number of ETo estimation methods have been developed with different degree of complexity and data requirement. The present study was carried out to develop artificial neural network (ANN) based reference crop evapotranspiration models corresponding to the ASCE’s best ranking conventional ETo estimation methods (Jensen et al. ASCE Manual and Rep. on Engrg. Pract. no. 70, 1990). Among the radiation methods, FAO-24 radiation (or Rad) method for arid and Turc method for humid region, and among the temperature methods, FAO-24 Blaney–Criddle (or BC) method were studied. The ANN architectures corresponding to the above three less data-intensive methods were developed for four CIMIS (California Irrigation Management Information System) stations, namely, Davis, Castroville, Mulberry, and West Side Field station. The comprehensive ANN architecture developed by Kumar et al. (J Irrig Drain Eng 128(4):224–233, 2002) corresponding to Penman–Monteith (PM) ETo for Davis was also tried for the other three stations. Daily meteorological data for a period of more than 10 years (01 January 1990 to 30 June 2000) were collected from these stations and were used to train, test, and validate the ANN models. Two learning schemes, namely, standard back-propagation with learning rate of 0.2 and standard back-propagation with momentum having learning rate of 0.2 and momentum term of 0.95 were considered. ETo estimation performance of the ANN models was compared with the FAO-56 PM method. It was found that the ANN models gave better closeness to FAO-56 PM ETo than the best ranking method in each category (radiation and temperature). Thus these models can be used for ETo estimation in agreement with climatic data availability, when not all required climatic variables are observed.     

A mathematical model for border irrigation II. Vertical and horizontal recession phases

Summary This paper, second in a series of three, develops a mathematical model, using the volume balance approach, to simulate vertical and horizontal recession of border irrigation. An equation is proposed for computing Manning's roughness factor N in both laminar and transitional flow regimes in recession phases. The model has four parameters which can be determined experimentally. Experimental data from ten vegetated as well as nonvegetated borders were used to verify the model. Average difference (AD) between calculated and observed vertical recession times was less than 4.4 min, and between calculated and observed horizontal recession times less than 4.6 min for the ten experimental data sets. Average relative error (ARE) in computed horizontal recession was less than 13% for these data sets. The model was found to be especially accurate for Reynold's number between 1,800 and 2,500.     

Behavioral hormoligosis in oviposition preference of Bemisia tabaci on cotton

The study on behavioral hormoligosis in oviposition preference in Bemisia tabaci (Genn.) on cotton was conducted, at Entomological Research Farm, Punjab Agricultural University (PAU), Punjab, India, during 2001 crop season and repeated in the same season. Multiple-choice test was followed for conducting the experiment. Quinalphos (250, 375, and 500), carbaryl (625, 938, and 1250), acephate (750, 1125, and 1500), endosulfan (438, 656, and 875), and fenvalerate (25, 38, and 50 g ai/ha) were repeatedly sprayed on potted plants of American cotton (var. LH-1556). The impact of these insecticides was evaluated in term of oviposition preference by B. tabaci to treated plants. Also, it investigated changes in biochemical components of treated cotton leaves and the correlation with oviposition preference. The results revealed that, fenvalerate treated plants were more preferred by whitefly for oviposition. Maximum number of eggs was observed on fenvalerate treated plants, 38, 50, and 25 g/ha (39.3, 37.3, and 36.1 eggs/leaf, respectively) followed by acephate 1500 g/ha (26.9 eggs/ leaf) compared with untreated control (14.1 eggs/leaf). Almost similar trend of results was observed in the repeated experiment. The results obtained from biochemical studies revealed that all the insecticidal treatments caused reduction in total sugars compared with untreated control except fenvalerate and low dose of quinalphos. All insecticides caused increase in total free amino acids and brought significant changes in total phenols and pH value of treated plants. These results have confirmed the behavioral hormoligosis in oviposition preference that induced by fenvalerate and acephate in B. tabaci, which may be one of the causes behind its resurgence on plants repeatedly treated with these insecticides.     

Climatic Constraints to the Potential of Microsphaeropsis amaranthi as a Bioherbicide for Common Waterhemp

ABSTRACT The fungal plant pathogen Microsphaeropsis amaranthi is a candidate bioherbicide for the control of weedy Amaranthus species since it grows and sporulates readily in culture, is a pathogen of a number of important weed species, and is host-restricted to the family Amaranthaceae. This study was designed to determine the optimum and limiting environmental conditions for the efficacy of foliar applications of M. amaranthi for the control of common waterhemp. The greatest disease severity and the greatest plant biomass reductions were found when a prolonged leaf wetness period of >/= 12 h at 18 to 24 degrees C was provided after application. Disease severity and plant biomass reductions were greater when plants were treated at an earlier stage of development. Disease severity and impact were limited when shorter leaf wetness periods were provided, with negligible disease observed on plants provided with 相似文献   

DArTseq physical mapping of QTLs linked to Karnal bunt (Tilletia indica) resistance in two historical wheat populations

Karnal bunt, a disease of wheat, durum, rye, and triticale, is subject to strict quarantine restrictions worldwide. The disease is considered a major threat to food security, due to its use as a non-tariff trade barrier by several wheat-importing countries. In this paper, we analysed seven years of phenotypic data to search for quantitative trait loci (QTLs) associated with resistance in common wheat, validated the QTLs using an independent population, and assessed the potential of genomic selection as a tool for pre-emptive breeding. The QTL study used phenotypic data collected from artificially inoculated field experiments involving two historical Karnal bunt resistance populations: WH542 × HD29 and WH542 × W485. QTL analyses detected four significant (p < 0.001) QTLs on chromosomes 1A, 3A, 4B, and 6B, which explained between 13.7% and 15.7% of the phenotypic variation. A panel of 130 cultivars was used to validate QTL effects. These were genotyped with the same DArTseq protocol, and two of the four QTLs were significantly (p < 0.001) associated with Karnal bunt resistance in the validation panel. The potential of genomic selection was investigated by comparing accuracies of a model trained with all available markers and a model based solely on validated QTL information from the biparental populations. Genomic prediction accuracy, based on the two scenarios, averaged 0.43 and 0.33, respectively, suggesting that even in situations where phenotyping is difficult due to quarantine restrictions, the prospects for pre-emptive breeding against Karnal bunt are encouraging, and resources are now available that will reduce the cost burden.     

Isotope-edited nuclear magnetic resonance: novel methodologies for investigating metabolism

While the use of NMR and stable isotopes in metabolism studies is hardly new, it is only recently that isotope-edited NMR spectroscopy has been applied in kinetic studies of glyphosate metabolism of soil microbes. NMR can detect multiple species simultaneously and non-destructively, yielding valuable information on structural identification of metabolites. T riple R esonance I sotope ED ited spectroscopy (TRIED), [²H]NMR, and [²H–¹³C] INEPT (I nsensitive N ucleus E nhancement through P olarization T ransfer) are three isotope-edited techniques which have been used in combination to examine the microbial degradation of glyphosate (N-phosphonomethylglycine). Using ¹³C- and ¹⁵N-labeled glyphosate, TRIED can detect multiple metabolites in crude matrices at submicrogram levels, an improvement over earlier techniques where milligrams were needed. It can detect 500 nanograms of ¹³C–¹⁵N-labeled compound in a crude sample (1 : 1400 mass ratio), only a few hours work being required. [²H]NMR and [²H–¹³C]INEPT were also used as complementary techniques to further examine metabolites whose ¹³C–¹⁵N bond has been cleaved. The three-isotope-edited methods produced results consistent with both radioactivity and HPLC analyses. Accordingly, we are able to detect minute levels of metabolites in the presence of complex mixtures, minimizing the costs and time of sample purification. ©1999 Society of Chemical Industry