Estimation of genetic variability and population structure in Sapindus trifoliatus L., using DNA fingerprinting methods

Genetic variability and population structure of Sapindus trifoliatus L. (Sapindaceae), collected from Gujarat, Karnataka and Uttar Pradesh states were estimated using three DNA fingerprinting methods viz., random amplified polymorphic DNA (RAPD), directed amplification of minisatellite DNA (DAMD) and inter-simple sequence repeats (ISSR). The cumulative data analysis carried out for all three markers showed 69.42 % polymorphism. The intra-population genetic diversity analysis revealed the highest values of Nei’s genetic diversity (0.16), Shannon information index (0.24) and polymorphic loci (43.99 %) among Bhavnagar (BH) population, whereas lowest values were found in Junagarh (JU) population. The maximum inter-population average genetic distance (0.20) was between Allahabad (AL) and JU populations. Analysis of molecular variance (AMOVA) showed highest percentage of variation among individuals of populations (56 %) followed by 25 % among populations and 19 % among regions. Principal coordinate analysis and UPGMA dendrogram revealed that genetic diversity was in congruence with the geographical diversity. The data strongly suggest that low genetic flow, geographic isolation and to some extent genetic drift are the major factors responsible for high genetic differentiation. Preservation of genetic diversity of S. trifoliatus is important, both to promote adaptability of the populations to changing environment as well as to preserve a large gene pool for future genetic improvement. The present study using RAPD, DAMD and ISSR profiles of S. trifoliatus provide the means of rapid characterization of accessions within the populations, and thus enable the selection of appropriate accessions for further utilization in conservation and prospection programs of this important plant genetic resource.     

Prediction of citrus canker epidemics generated through different inoculation methods

Citrus canker epidemics were generated with 10^8?cfu/ml of Xanthomonas axonopodis pv. citri (ex Hasse) on Citrus limonia cv. China lemon, Citrus reticulate cv. kinnow, Citrus jambhiri, Citrus reticulate cv. Feutral’s early and Citrus limettioides using four inoculation techniques. Natural inoculum was also relied upon for infection. Overall, the injection infiltration method led to maximum disease generation followed by spray, pinprick and smear inoculation methods. Citrus canker incidence along with environmental data were recorded and subjected to stepwise regression analysis. Except relative humidity, the relationship of weekly air temperature (maximum and minimum), rainfall and wind speed with citrus canker disease development in all citrus cultivars was positively correlated and best explained by linear regression. Overall, two environmental variable model containing maximum and minimum air temperature fit the data well explaining 93% variability in disease development. The observed citrus canker incidence values and those predicted by the model were close in most of citrus cultivars. This two environmental variable model can be used to issue advance warning forecasts for the timely management of the citrus canker in Pakistan.     

RAPD analysis of local bell pepper genotypes in relation with powdery mildew incidence and fruit yield: Managing disease by single chemical molecule

Abstract

A field study was conducted to investigate powdery mildew disease incidence and fruit yield of locally available bell pepper genotypes by Kharif 2004 and Rabi 2005. The study includes a single chemical molecule in managing the powdery mildew disease during both the seasons. Field studies include five chemical treatments (T₁ to T₅) plus one water spray control and an untreated control in five replications each. The result shows that out all treatments T₅ was best in controlling the powdery mildew disease in genotype Indra by 77.1 and 73.7% of disease decrease over control and 85.3 and 95.7% increase in yield over control respectively during Kharif and Rabi. The next best performing genotypes were Arka Basant and California Wonder in terms of less disease incidence and high yield. Further, the study was extended to relate the selected varieties for its genetic diversity using Random Amplified Polymorphic DNAs, with respect to the disease incidence and yield. The highest genetic dissimilarity of 49% was noticed between the genotypes Indra and Arka Gaurav having contrasting characters such as high and low fruit yield, respectively. The lowest genetic diversity of 21% was noticed between the genotypes Arka Mohini and California Wonder that were similar in most of the morphological characters, fruit yield and susceptibility to the powdery mildew disease. Based on the molecular data, a remarkable difference was exhibited by the commercially grown bell pepper genotypes.     

Detection of Prunus necrotic ring spot virus in plum,cherry and almond by serological and molecular techniques from India

Stone fruits are cultivated in the temperate and sub-temperate regions of India. During surveys in stone fruit growing areas, viral symptoms were observed in almond, cherry and plum. These samples were brought to the laboratory for further detection at serological and molecular levels to check the presence of virus. In the present study, incidence of PNRSV is reported on plum (Prunus domestica), almond (Prunus dulcis) and cherry (Prunus avium) using serological and molecular techniques. Coat protein gene of PNRSV was amplified from almond, cherry and plum. This is the first molecular evidence of PNRSV on these stone fruits reported from India.     

Polyunsaturated Fatty Acids: Biotechnology

ABSTRACT

Polyunsaturated fatty acids like EPA and DHA have attracted a great attention due to their beneficial effects on human health. At present, fish oil is the major source of EPA and DHA. Various alternative sources are being explored to get these essential fatty acids. Genes encoding enzymes involved in the biosyntheses of PUFAs have been identified, cloned and gene prospecting becomes a novel method for enhanced PUFA production. Desaturase and elongase genes have important biotechnological appeal from genetic engineering point of view. This review highlights the research and results on such enzymes.     

A communication network within the cytoplasmic domain of toll-like receptors has remained conserved during evolution

Toll/IL-1R (TIR) domain, that is, the cytoplasmic domain, in toll-like receptors (TLRs) from different species showed high sequence conservation in stretches spread across the surface as well as the core of the domain. To probe the structure–function significance of these residues, especially those coming from the core of TIR domains, we analyzed molecular dynamics trajectories of sequence similarity based models of human TIR domains. This study brought forth that N-terminal of the TIR domain simultaneously interacts with the flanking residues of the BB loop and central β-sheets. At the same time, residues of the central β-strands form favorable contacts with the DD loop and C-terminal, thus forming a two-way circuit between the N- and C-termini. In this work, the array of intradomain interactions is termed as communication network. Importantly, the “hubs” of this communication network were found to be conserved in all human TLRs. Earlier mutagenesis–function correlation work brought forth that certain mutations in the “core” of the TIR domain of TLR4 (e.g. in IFI767–769AAA and L815A) led to almost complete abrogation of signaling and reasoning for this dramatic loss-of-function has remained unclear, since these sites are not surface exposed. Using MD studies, we show here that this communication network gets disrupted in mutants of human TLR4 which were earlier reported to be functionally compromised. Extension of MD studies to heterodimer of TLR1/2 suggested that this evolutionarily conserved communication network senses the interactions formed upon dimerization and relays it to surfaces which are not involved in direct interdomain contacts.