Field response of chickpea to inoculation withGlomus versiforme

The response ofCicer arietinum to inoculation withGlomus versiforme under field conditions was investigated in a phosphorus deficient sandy loam soil. Inoculation with the mycorrhizal fungusGlomus versiforme increased the rate of VAM development in chickpea. The weight of nodules and the number of nodules per plant were higher in inoculated than in uninoculated plants. The phosphorus content of the shoots and its total uptake, were increased by either the application of single super-phosphate, or by inoculation withG. versiforme. Inoculation increased shoot dry weights and grain yields by 12% and 25% respectively, as compared with the 33% and 60% increases respectively produced by P-treated plants.     

Molecular characterization of Macrophomina phaseolina and Fusarium species by a single primer RAPD technique

Charcoal root rot and wilt, are two economically important diseases of many crop plants in North and South America, Asia and Africa and some parts of Europe. Genetic variation in 43 isolates of Macrophomina phaseolina and 22 isolates of Fusarium species, collected from geographically distinct regions over a range of hosts, was studied using random amplified polymorphic DNA (RAPD) markers. Initially, 210 arbitrary nucleotide (10-mer) primers were tested for amplification of genomic DNA of one M. phaseolina isolate, 70 primers amplified the genomic DNA of M. phaseolina. One primer OPA-13 (5'-CAGCACCCAC-3') produced fingerprint profiles, which clearly distinguished between the different isolates of M. phaseolina. UPGMA analysis classified these isolates into five major groups. By primer OPA-13, 22 isolates of pathogenic and non-pathogenic Fusarium species of different formae-speciales and races, were also distinguished from M. phaseolina. This marker is useful for distinguishing between these two important plant pathogens irrespective of hosts, virulence spectrum and races. This is the first report of reliable diagnosis of two soilborne pathogens (root/collar rot and wilt causing pathogens) at the level of isolates, formae-speciales and races by a single primer RAPD procedure with uniform PCR conditions.     

Construction of a Genetic Linkage Map and Identification of QTLs for Seed Weight and Seed Size Traits in Lentil (Lens culinaris Medik.)

Seed weight and seed size both are quantitative traits and have been considered as important components of grain yield, thus identification of quantitative trait loci (QTL) for seed traits in lentil (Lens culinaris) would be beneficial for the improvement of grain yield. Hence the main objective of this study was to identify QTLs for seed traits using an intraspecific mapping population derived from a cross between L. culinaris cv. Precoz (seed weight-5.1g, seed size-5.7mm) and L. culinaris cv. L830 (seed weight-2.2g, seed size-4mm) comprising 126 F₈-RILs. For this, two microsatellite genomic libraries enriched for (GA/CT) and (GAA/CTT) motif were constructed which resulted in the development of 501 new genomic SSR markers. Six hundred forty seven SSR markers (including 146 previously published) were screened for parental polymorphism and 219 (33.8%) were found to be polymorphic among the parents. Of these 216 were mapped on seven linkage groups at LOD4.0 spanning 1183.7cM with an average marker density of 5.48cM. Phenotypic data from the RILs was used to identify QTLs for the seed weight and seed size traits by single marker analysis (SMA) followed by composite interval mapping (CIM) which resulted in one QTL each for the 2 traits (qSW and qSS) that were co-localized on LG4 and explained 48.4% and 27.5% of phenotypic variance respectively. The current study would serve as a strong foundation for further validation and fine mapping for utilization in lentil breeding programs.     

Candidate Gene Identification with SNP Marker-Based Fine Mapping of Anthracnose Resistance Gene Co-4 in Common Bean

Anthracnose, caused by Colletotrichum lindemuthianum, is an important fungal disease of common bean (Phaseolus vulgaris). Alleles at the Co–4 locus confer resistance to a number of races of C. lindemuthianum. A population of 94 F_4:5 recombinant inbred lines of a cross between resistant black bean genotype B09197 and susceptible navy bean cultivar Nautica was used to identify markers associated with resistance in bean chromosome 8 (Pv08) where Co–4 is localized. Three SCAR markers with known linkage to Co–4 and a panel of single nucleotide markers were used for genotyping. A refined physical region on Pv08 with significant association with anthracnose resistance identified by markers was used in BLAST searches with the genomic sequence of common bean accession G19833. Thirty two unique annotated candidate genes were identified that spanned a physical region of 936.46 kb. A majority of the annotated genes identified had functional similarity to leucine rich repeats/receptor like kinase domains. Three annotated genes had similarity to 1, 3-β-glucanase domains. There were sequence similarities between some of the annotated genes found in the study and the genes associated with phosphoinositide-specific phosphilipases C associated with Co-x and the COK–4 loci found in previous studies. It is possible that the Co–4 locus is structured as a group of genes with functional domains dominated by protein tyrosine kinase along with leucine rich repeats/nucleotide binding site, phosphilipases C as well as β-glucanases.     

Polyamines in normal and auxin-induced strawberry fruit development

The possible involvement of polyamines during strawberry ( Fragaria × ananassa Duch.) fruit development was investigated. Putrescine, spermidine, and spermine were identified in strawberry receptacles and achenes at all stages of development. Total (free) polyamine levels decreased from a maximum of 485 nmol g⁻¹ fresh weight at pollination to a minimum of 55 nmol g⁻¹ fresh weight in ripe receptacles. Total polyamine concentrations during corresponding stages of development were consistently higher in achenes than in receptacles, and ranged from 891 to 203 nmol g⁻¹ fresh weight. Removal of achenes from the surface of developing receptacles 10 days after pollination reduced receptacle growth, and re-initiation of growth by application of 1 m M α-naphtaleneacetic acid (α-NAA) was accompanied by a rapid increase in polyamine concentrations 24 h after treatment. Polyamine content per receptacle increased >3-fold in normally developing receptacles and in de-achened, auxin-treated receptacles 10 days after removal of achenes, but did not increase during this period in de-achened receptacles not treated with exogenous auxin. α-NAA increased growth and polyamine levels to a greater extent than the structurally related, but less effective auxin, β-NAA. Polyamine concentrations in receptacles with intact achenes remained similar to those of auxin depleted (de-achened) receptacles, implying that the concentration of these compounds may not be limiting following achene removal.     

Genome-wide distribution and organization of microsatellites in plants: an insight into marker development in Brachypodium

Plant genomes are complex and contain large amounts of repetitive DNA including microsatellites that are distributed across entire genomes. Whole genome sequences of several monocot and dicot plants that are available in the public domain provide an opportunity to study the origin, distribution and evolution of microsatellites, and also facilitate the development of new molecular markers. In the present investigation, a genome-wide analysis of microsatellite distribution in monocots (Brachypodium, sorghum and rice) and dicots (Arabidopsis, Medicago and Populus) was performed. A total of 797,863 simple sequence repeats (SSRs) were identified in the whole genome sequences of six plant species. Characterization of these SSRs revealed that mono-nucleotide repeats were the most abundant repeats, and that the frequency of repeats decreased with increase in motif length both in monocots and dicots. However, the frequency of SSRs was higher in dicots than in monocots both for nuclear and chloroplast genomes. Interestingly, GC-rich repeats were the dominant repeats only in monocots, with the majority of them being present in the coding region. These coding GC-rich repeats were found to be involved in different biological processes, predominantly binding activities. In addition, a set of 22,879 SSR markers that were validated by e-PCR were developed and mapped on different chromosomes in Brachypodium for the first time, with a frequency of 101 SSR markers per Mb. Experimental validation of 55 markers showed successful amplification of 80% SSR markers in 16 Brachypodium accessions. An online database 'BraMi' (Brachypodium microsatellite markers) of these genome-wide SSR markers was developed and made available in the public domain. The observed differential patterns of SSR marker distribution would be useful for studying microsatellite evolution in a monocot-dicot system. SSR markers developed in this study would be helpful for genomic studies in Brachypodium and related grass species, especially for the map based cloning of the candidate gene(s).     

Fungi on Acacia arabica Linn

Summary The paper deals with three new species of Deuteromycetous fungi e.g.Diplodia acaciae, Cytospora acaciae, andFusicoccum indicum collected on dead stems ofAcacia arabica Linn.     

New DNA data from a transthyretin nuclear intron suggest an Oligocene to Miocene diversification of living South America opossums (Marsupialia: Didelphidae)

Phylogenetic relationships of 19 species of didelphid marsupials were studied using two nuclear markers, the non-coding transthyretin intron 1 (TTR) and the coding interphotoreceptor retinoid binding protein exon 1 (IRBP), and two mitochondrial genes, the protein-coding cytochrome b (cyt-b) and the structural 12S ribosomal DNA (12S rDNA). Evolutionary dynamics of these four markers were compared to each other, revealing the appropriate properties presented by TTR intron 1 together with its well supported and resolved phylogenetic signal. Nuclear markers supported the monophyly of medium and large-sized opossums Metachirus+(Chironectes, Lutreolina, Didelphis, Philander), and the paraphyly of mouse-sized opossums, with the genera Gracilinanus, Thylamys, and Marmosops as a sister group to medium and large-sized didelphids. Conflicting branching patterns between mitochondrial and nuclear data involved the phylogenetic position of Marmosa-Micoureus-Monodelphis relative to other mouse-sized opossums. Nuclear phylogenetic inferences among genera were confirmed by the presence of synapomorphic indels observed in TTR intron 1. A Bayesian relaxed molecular clock dating of didelphid evolution using nuclear markers estimated their origin in the Middle Eocene (39.8 million years ago), with subsequent diversification during the Oligocene (Deseadan) and Miocene.