Molecular mapping of a locus controlling resistance to Albugo candida in Indian mustard

Brassica juncea (L.) Czern & Coss is widely grown as an oilseed crop in the Indian subcontinent. White rust disease caused by Albugo candida (Pers.) Kuntze is a serious disease of this crop causing considerable yield loss every year. The present study was undertaken to identify molecular markers for the locus controlling white rust resistance in a mustard accession, BEC‐144, using a set of 94 recombinant inbred lines (RILs). The screening of individual RILs using an isolate highly virulent on the popular Indian cultivar ‘Varuna’ revealed the presence of a major locus for rust resistance in BEC‐144. Based on screening of 186 decamer primers employing bulked segregant analysis (BSA), 11 random amplified polymorphic DNA markers were identified, which distinguished the parental lines and the bulks. Five of these markers showed linkage with the rust resistance locus. Two markers, OPN0_l000 and OPB06₁₀₀₀, were linked in coupling and repulsion phases at 9.9 cM and 5.5 cM, respectively, on either side of the locus. The presence of only two double recombinants in a population of 94 RILs suggested that the simultaneous use of both markers would ensure efficient transfer of the target gene in mustard breeding programmes.     

Profiling the thermoelectric power of semiconductor junctions with nanometer resolution

We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices.     

Initiating and cancer-propagating cells in TEL-AML1-associated childhood leukemia

Understanding cancer pathogenesis requires knowledge of not only the specific contributory genetic mutations but also the cellular framework in which they arise and function. Here we explore the clonal evolution of a form of childhood precursor-B cell acute lymphoblastic leukemia that is characterized by a chromosomal translocation generating a TEL-AML1 fusion gene. We identify a cell compartment in leukemic children that can propagate leukemia when transplanted in mice. By studying a monochorionic twin pair, one preleukemic and one with frank leukemia, we establish the lineal relationship between these "cancer-propagating" cells and the preleukemic cell in which the TEL-AML1 fusion first arises or has functional impact. Analysis of TEL-AML1-transduced cord blood cells suggests that TEL-AML1 functions as a first-hit mutation by endowing this preleukemic cell with altered self-renewal and survival properties.     

Specific identification of Pasteurella multocida serogroup-A isolates by PCR assay

A polymerase chain reaction (PCR) assay targeting the hyaC-hyaD gene was developed and used to identify strains of Pasteurella multocida belonging to serogroup-A. A set of serogroup-specific-PCR primers amplified a 564 bp product from genomic DNA prepared from bacterial cells or directly from bacterial colonies. This method detected as low as 10 ng of bacterial DNA and had a specificity of 100% for P. multocida serogroup-A. A nested PCR method yielded a single 374 bp product. All fifty isolates were also shown to be identical by restriction fragment length polymorphism (RFLP) analysis of the PCR products after digestion with BglII.     

Role of Excretory–Secretory Metabolites of Fasciola gigantica in Modulating Delayed-type Hypersensitivity in Rats

The role of excretory-secretory metabolites of Fasciola gigantica in modulating the delayed type of hypersensitivity in the host (rats) was investigated. Eighteen rats of either sex, aged 3-4 months, were assigned to three groups of 6 animals each. Rats in group 1 served as non-inoculated controls and each rat in this group was administered only Freund's complete adjuvant on day 7. Animals in groups 2 and 3 were administered inoculation dose(s) of somatic F gigantica antigen (SFgA) and excretory-secretory F gigantica antigens (ESFgA) according to the experimental schedule. The delayed-type hypersensitivity was monitored by assessing alterations in the foot pad thickness, its histopathology and lymphocyte proliferation assay. It was observed that the ESFgA caused diminution in delayed-type hypersensitivity response to a significant level (p <0.01) against SFgA in rats. This finding was further confirmed by lower stimulation indices of peripheral blood mononuclear cell in rats sensitized with ESFgA prior to inoculation of SFgA (group 1) than in nonsensitized rats receiving only SFgA (group 2).     

Low level of polymorphism detected by SSR probes in bread wheat

In-gel hybridization patterns were studied in a set of nine diverse bread wheat ( Triticum aestivum L. em. Thell) genotypes using 23 simple sequence repeat (SSR) probes in combination with 14 different restriction enzymes. Multilocus fingerprints due to SSR probes, shown earlier to be characteristic of a majority of plant genomes, were not obtained and only a very low level of polymorphism was detected when using as many as 142 probe-enzyme combinations. The hybridization of a prominent solitary high molecular weight fragment (> 23 kb) with a number of SSR probes suggested the presence of these SSRs (microsatellites) within the long stretches of repeated DNA sequences. This indicates that the genome of bread wheat differs from that of other plants in the organization and distribution of SSRs and that SSR probes detect very little polymorphism.     

Foliar fungal disease‐resistant introgression lines of groundnut (Arachis hypogaea L.) record higher pod and haulm yield in multilocation testing

Introgression lines (ILs) of groundnut with enhanced resistance to rust and late leaf spot (LLS) recorded increased pod and haulm yield in multilocation testing. Marker‐assisted backcrossing (MABC) approach was used to introgress a genomic region containing a major QTL that explains >80% of phenotypic variance (PV) for rust resistance and 67.98% PV for LLS resistance. ILs in the genetic background of TAG 24, ICGV 91114 and JL 24 were evaluated for two seasons to select 20 best ILs based on resistance, productivity parameters and maturity duration. Multilocation evaluation of the selected ILs was conducted in three locations including disease hot spots. Background genotype, environment and genotype × environment interactions are important for expression of resistance governed by the QTL region. Six best ILs namely ICGV 13192, ICGV 13193, ICGV 13200, ICGV 13206, ICGV 13228 and ICGV 13229 were selected with 39–79% higher mean pod yield and 25–89% higher mean haulm yield over their respective recurrent parents. Pod yield increase was contributed by increase in seed mass and number of pods per plant.