Comparison between ELISA and bio tin-la belled probes from cloned cDNA of potato virus X for the detection of virus in crude tuber extracts

Diseases caused by potato virus X (PVX) are of significant agronomic importance, and early detection is vital. Biotinylated DNA probes were prepared by random-primed labelling from cDNA inserts and used for the detection of PVX in crude extracts of infected tubers. The minimum detection level in these extracts is in the order of femtograms of PVX RNA. Comparison with ELISA showed that the hybridization method is 100–250 times more sensitive. Probes prepared by this method are highly specific for target RNA even in crude tuber extracts.     

Genes for race-specific resistance to yellow rust (Puccinia striiformis) in Indian wheat cultivars

Seedlings of Indian wheat cultivars (Kalyansona, Sonalika, WL711 and eight others released commercially) were tested with 13 British and four alien races of Puccinia striiformis. The data indicated the probable presence of the resistance gene Yr2 in the three cultivars named above and in six of the others. Reactions of the remaining two cultivars, PWB12 and WL2265, were consistent with the presence of the gene 177. The presence of Yr2 in Kalyansona, Sonalika and WL711 was supported by evidence from crosses between them and with Heines VII, which is known to carry Yr2. In crosses of Sonalika with a susceptible cultivar, Kharchia Local and also with WL711, tests of F1, F2 and F3 generations indicated that, in addition to Yr2 , Sonalika possesses at least two other genes. Both these genes were difficult to detect but the F3 data supported the hypothesis that there is a single partially recessive gene giving resistance to alien race 6E16 and a different, possibly complementary, gene system effective against another alien race, 39E134. The presence of resistance in addition to Yr2 was also detected in WL711 and HD2329.     

Effects of two surfactant series on the absorption and translocation of 14C-glyphosate in sicklepod and prickly sida

The weed species, prickly sida (Sida spinosa L.) and sicklepod (Senna obtusifolia L.), were treated with ¹⁴C-glyphosate alone and formulated with different polyethlylane oxide (PEO) surfactants in tallow amine ethoxylate and non-ionic alkoxylate series to determine the amount of ¹⁴C-glyphosate absorption and translocation. The surface tension, contact angle, and ¹⁴C-glyphosate distribution were significantly affected by both the presence of different waxes on the plants and by the addition of surfactants to the glyphosate. The surface and contact angle values of the surfactants, with and without glyphosate, showed a significant increase as the PEO number increased in both surfactant series. A higher absorption of the ¹⁴C-glyphosate was recorded for S. spinosa compared with S. obtusifolia. The absorption and translocation of the ¹⁴C-glyphosate increased with the increase in the PEO number of tallow amine ethoxylate. In the case of the non-ionic alkoxylate surfactant series, an increase in the absorption of ¹⁴C-glyphosate was recorded when the surface tension and contact angle values decreased. There was no significant difference in the translocation values obtained in the two species after the addition of the surfactants. The amount of ¹⁴C-glyphosate absorbed by the treated leaf was significantly higher in the case of S. spinosa compared with S. obtusifolia. A linear relationship was observed with the physical properties, ¹⁴C absorption, and the efficacy of glyphosate with the addition of the non-ionic alkoxylate surfactant series. The percentage control was higher with the higher PEO surfactant in the tallow amine ethoxylate surfactant series and with the lower PEO surfactant in the non-ionic alkoxylate surfactant series as the two series are chemically different.     

Assessment of Seasonal and Site-Specific Variations in Soil Physical, Chemical and Biological Properties Around Opencast Coal Mines

Coal mining adversely affects soil quality around opencast mines. Therefore, a study was conducted in 2010 and 2011 to assess seasonal and site-specific variations in physical, chemical, and biological properties of soil collected at different distances from mining areas in the Jharia coalfield, India. Throughout the year, the soil in sites near coal mines had a significantly higher bulk density, temperature, electrical conductivity, and sulfate and heavy metal contents and a significantly lower water-holding capacity, porosity, moisture content, pH, and total nitrogen and available phosphorus contents, compared with the soil collected far from the mines. However, biological properties were site-specific and seasonal. Soil microbial biomass carbon (MBC) and nitrogen (MBN), MBC/MBN, and soil respiration were the highest during the rainy season and the lowest in summer, with the minimum values in the soil near coal mines. A soil quality index revealed a significant effect of heavy metal content on soil biological properties in the coal mining areas.     

Dynamics of the functional groups in the weed flora of dryland and irrigated agroecosystems in the Gangetic plains of India

The relative abundance of the weed functional types in dryland and irrigated rice in the Kharif (summer) crop field and dryland lentil and wheat in the irrigated Rabi (winter) crop field was studied at the agricultural farm of Banaras Hindu University, Varanasi, India. A total of 22 species, belonging to 17 families, was recorded in the dryland and irrigated rice ecosystems and 18 species, belonging to eight families, were recorded in the dryland lentil and irrigated wheat ecosystems. The Importance Value Index (IVI) of the hemicryptophytes showed an increasing trend with the crop growth period in the case of the dryland rice, whereas in the irrigated rice plots, a reduction in the IVI of the hemicryptophytes, with a related increase in the importance of the therophytes, was observed as the crop attained maturity. Also, the trend of a decreased IVI was observed for the geophytes in the fertilized dryland rice plots. The principal components analysis (PCA) ordination showed the uniqueness of the crop plot in terms of weed species composition. The PCA analysis of the functional types on the basis of the crop plots indicated that the hemicryptophyte and therophyte weed species composition was heavily altered at the initial and final sampling, although the weed flora was dominated by the therophytes and geophytes. These results suggest the prioritization of hierarchical temporal management options for the functional weed types in different crop plots and that this approach warrants further investigation.     

小麦品种川麦107对条锈病成株抗性的QTL定位

【目的】发掘川麦107中的条锈病成株抗性基因及与其紧密连锁的分子标记,为小麦持久抗性育种提供基因和分子标记辅助选择工具。【方法】在墨西哥国际玉米小麦改良中心(CIMMYT)Toluca试验站、中国成都和雅安3个环境下,对川麦107/Avocet-YrA组合的F5代重组自交系(recombinant inbred line,RIL)群体进行了小麦条锈病成株抗性鉴定,在此基础上利用SSR标记和复合区间作图法对成株抗性基因进行定位。【结果】在1B染色体长臂远端的Xcwem32和Xgwm818位点之间(连锁距离3.9cM)检测到1个主效QTL,暂定名为QYr.saas-1BL。该主效QTL在3个试验环境下分别解释19.3%、16.9%和27.4%的表型变异。【结论】QYr.saas-1BL是川麦107中对条锈病有持久抗性的成株抗性QTL。     

采用土壤质量指数评估施肥对集约型稻麦轮作系统中土壤物理性质的影响

Soil quality assessment has been suggested as an effective tool for evaluating sustainability of soil and crop management practices.The objective of this study was to develop a sensitive soil quality index(SQI) based on bulk density(BD),water-holding capacity(WHC),water-stable aggregates(WSA),aggregate mean weight diameter(AMWD),total organic C(TOC) and C input to evaluate the important rice-wheat cropping system on an Inceptisol in India.A long-term experiment has been conducted for 18 years at the Indian Council of Agricultural Research-Indian Institute of Farming Systems Research,Modipuram,India.The treatments selected for this study were comprised of a no-fertilizer control and N,P and K fertilizers(NPK) combined with Zn and S fertilizers(NPK+ Zn+S),farmyard manure(NPK+FYM),green gram residues(NPK+GR) and cereal residues(NPK+CR),laid out in a randomized complete block design with three replications.Soil samples were collected and analyzed for BD,WHC,WSA and TOC.Correlation analysis revealed that both rice and wheat yields signi?cantly increased with the increases in AMWD,TOC and C input,but decreased with the increase in BD.The SQI values were then generated based on regression analysis of BD,WSA,AMWD,TOC and C input with rice and wheat yields for the 0–15 and 15–30 cm soil layers,respectively.Regression analyses between crop yields and SQI values showed a quadratic type of relation with the coeffcient of determination(R~2) varying from 0.78 to 0.89.With regard to soil sustainability,applying crop residues to both rice and wheat could maintain soil quality for a longer period,whereas the highest yields of both the crops were recorded in the NPK+Zn+S treatment.The regression equations developed in this study could be used to monitor soil quality in a subhumid tropical rice-wheat cropping system.     

Evaluation of a PCR assay for identification and differentiation of Campylobacter fetus subspecies

Objective To evaluate a polymerase chain reaction assay for identification of Campylobacter fetus and differentiation of the defined subspecies.
Design Characterisation of bacterial strains by traditional phenotyping, polymerase chain reaction, a probabilistic identification scheme and macrorestriction profiling using pulsed field gel electrophoresis.
Procedure The results of identification of 99 bacterial strains as determined by conventional phenotyping or by poly-merase chain reaction were compared. Two of these were type strains of C fetus subsp fetus and C fetus subsp venerealis ; the remaining strains were field isolates putatively identified as C fetus . In cases where the subspecies identity was disputed, isolates were identified by means of a probabilistic identification scheme and by macrorestriction profiling.
Results The agreement between strain identities initially suggested by traditional phenotypic methods and the PCR assay was found to be 80.8%. The polymerase chain reaction proved to be a reliable technique for the species and subspecies identification of C fetus ; equivocal results were obtained in only two instances. Initial misidentifications by conventional phenotyping methods were attributed to methodological differences used in various laboratories.
Conclusion Our results indicate that misidentification of C fetus i n routine diagnostic laboratories may be relatively common. The PCR assay evaluated gave rapid and reproducible results and is thus a valuable adjunctive method for the identification of C fetus and subsequent subspecies differentiation.     

Lantana invasion: An overview

We review the key features of Lantana ( Lantana camara L.), an invasive plant species considered to be among the world's 10 worst weeds. Lantana occurs in diverse habitats and on a variety of soil types, and its spread is encouraged by animal activities and by human disturbances, such as cultivation, road construction, and changes in fire regimes. Lantana is morphologically distinct in the different regions of its invasive range compared to those regions in its native range. The biological attributes contributing to the success of Lantana as an invader species include: fitness homeostasis, phenotypic plasticity, dispersal benefits from destructive foraging activities, widespread geographic range, vegetative reproduction, fire tolerance, better competitive ability compared to native flora, and allelopathy. Mechanical, chemical and biological options for the eradication and control of Lantana are available. It is emphasized that ecosystem-level consequences of Lantana invasion, particularly on the biodiversity of native flora, are little understood and studies are needed to fulfill this knowledge gap.