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Hyderabad, India

Manimaran P.,Directorate of Rice Research
GM crops | Year: 2011

Bacillus thuringiensis (Bt), a gram positive soil bacteria was first identified and named by Japanese microbiologist Shigetane Ishiwata in 1901. During sporulation Bt produces proteinaceous parasporal crystal proteins called δ-endotoxins, or Cry proteins, which are insecticidal. Numerous Cry proteins have been isolated and characterized from different Bt strains with activity against insects, mites and nematodes. Sprayable formulations containing these Cry proteins as active ingredients have contributed significantly in the field of insect pest management. Since the first cloning of cry genes from Bt,1 scientists have successively demonstrated that plants could be genetically engineered to express these cry genes for the control of dreadful insect pests. Eventually, the first transgenic crop expressing Btcry1Ac gene in cotton was approved in 1996 for commercial cultivation in the USA to manage bollworms. Source

Andow D.A.,University of Minnesota | Bentur J.S.,Directorate of Rice Research
Entomologia Experimentalis et Applicata | Year: 2010

Monitoring changes in rare, recessive allele frequencies in natural populations can be accomplished using pedigreed individuals sampled from these populations. A pedigree keeps track of and limits the mating of sampled individuals, to preserve information about the genotype of the sampled individual in the phenotypes of its descendents. To estimate allele frequencies in a natural population using pedigreed crosses, four relations must be specified: a method to determine whether the pedigreed line carries the desired allele; a method to estimate the phenotypic frequency of the trait among the pedigreed lines and a credibility limit for the estimate; (the genetic relation between the phenotype frequency among the lines and the allele frequency in the natural population; and a method to estimate the probability that the first method did not detect the trait, assuming that the allele was present in the sampled individual. Knowledge about the segregation patterns of the allele enables specification of andBayesian statistics were used to estimate the phenotypic frequency of the trait among the pedigreed lines. The method determining whether the pedigreed line carries the desired allele will vary with the species and trait of concern. We focused on monitoring of vGm1, a recessive autosomal allele, and vGm2, a recessive sex-linked allele, which provide virulence against certain rice resistance genes in rice gall midge, Orseolia oryzae (Wood-Mason) (Diptera: Cecidomyiidae). We show how three pedigrees can be used to estimate these allele frequencies. An F1 field screen challenges the F1 offspring of sampled individuals on the rice differentials. A P1 test-cross mates the sampled individual with a homozygous lab colony for the allele of interest, and evaluates their offspring on the rice differentials. A conditional F1 test-cross takes the offspring from pedigrees that were negative in an F1 field screen, and test-crosses these offspring with the homozygous laboratory colony. We also indicate how to test for independent assortment when a double (or multiple) homozygote laboratory colony is used in a test-cross, how to test for differences among samples, and how to pool data to produce a single estimate based on a larger number of pedigreed lines. These methods may encourage the development of a variety of pedigreed monitoring strategies that could improve and prolong the use of scarce plant resistance alleles in rice and other plants. © 2010 The Authors. Journal compilation © 2010 The Netherlands Entomological Society. Source

Ladha J.K.,International Rice Research Institute | Reddy C.K.,Directorate of Rice Research | Padre A.T.,International Rice Research Institute | van Kessel C.,University of California at Davis
Journal of Environmental Quality | Year: 2011

Soil organic matter (SOM) is essential for sustaining food production and maintaining ecosystem services and is a vital resource base for storing C and N. Th e impact of long-term use of synthetic fertilizer N on SOM, however, has been questioned recently. Here we tested the hypothesis that long-term application of N results in a decrease in SOM. We used data from 135 studies of 114 long-term experiments located at 100 sites throughout the world over time scales of decades under a range of land-management and climate regimes to quantify changes in soil organic carbon (SOC) and soil organic nitrogen (SON). Published data of a total of 917 and 580 observations for SOC and SON, respectively, from control (unfertilized or zero N) and N-fertilized treatments (synthetic, organic, and combination) were analyzed using the SAS mixed model and by meta-analysis. Results demonstrate declines of 7 to 16% in SOC and 7 to 11% in SON with no N amendments. In soils receiving synthetic fertilizer N, the rate of SOM loss decreased. Th e time-fertilizer response ratio, which is based on changes in the paired comparisons, showed average increases of 8 and 12% for SOC and SON, respectively, following the application of synthetic fertilizer N. Addition of organic matter (i.e., manure) increased SOM, on average, by 37%. When cropping systems fl uctuated between fl ooding and drying, SOM decreased more than in continuous dryland or fl ooded systems. Flooded rice (Oryza sativa L.) soils show net accumulations of SOC and SON. Th is work shows a general decline in SOM for all long-term sites, with and without synthetic fertilizer N. However, our analysis also demonstrates that in addition to its role in improving crop productivity, synthetic fertilizer N signifi cantly reduces the rate at which SOM is declining in agricultural soils, worldwide. © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

Agarrwal R.,International Center for Genetic Engineering and Biotechnology | Bentur J.S.,Directorate of Rice Research | Nair S.,International Center for Genetic Engineering and Biotechnology
Journal of Integrative Plant Biology | Year: 2014

The Asian rice gall midge (Orseolia oryzae Wood-Mason) is a serious pest of rice that causes huge loss in yield. While feeding inside the susceptible host, maggots secrete substances that facilitate the formation of a hollow tube-like structure called gall and prevent panicle formation. The present investigation was carried out to get an account of biochemical changes occurring in the rice plant upon gall midge feeding. Metabolic profiling of host tissues from three rice varieties, namely, TN1, Kavya, and RP2068, exposed to gall midge biotype 1 (GMB1), was carried out using gas chromatography mass spectrometry (GC-MS). TN1 and GMB1 represented compatible interaction, while Kavya and GMB1 as well as RP2068 and GMB1 represented incompatible interactions. The current study identified several metabolites that could be grouped as resistance, susceptibility, infestation, and host features based on their relative abundance. These may be regarded as biomarkers for insect-plant interaction in general and rice-gall midge interaction in particular. © 2014 Institute of Botany, Chinese Academy of Sciences. Source

Swamy B.P.M.,Directorate of Rice Research | Swamy B.P.M.,International Rice Research Institute | Sarla N.,Directorate of Rice Research
Plant Molecular Biology Reporter | Year: 2011

Several reports on mapping and introgression of quantitative trait loci (QTLs) for yield and related traits from wild species showed their importance in yield improvement. The aim of this study was to locate common major effect, consistent and precise yield QTLs across the wild species of rice by applying genome-wide QTL meta-analysis for their use in marker-aided selection (MAS) and candidate gene identification. Seventy-six yield QTLs reported in 11 studies involving inter-specific crosses were projected on a consensus map consisting of 699 markers. The integration of 11 maps resulted in a consensuses map of 1,676 cM. The number of markers ranged from 32 on chromosome 12 to 96 on chromosome 1. The order of markers between consensus map and original map was generally consistent. Meta-analysis of 68 yield QTLs resulted in 23 independent meta-QTLs on ten different chromosomes. Eight meta-QTLs were less than 1.3 Mb. The smallest confidence interval of a meta-QTL (MQTL) was 179.6 kb. Four MQTLs were around 500 kb and two of these correspond to a reasonably small genetic distance 4.6 and 5.2 cM, respectively, and suitable for MAS. MQTL8. 2 was 326-kb long with a 35-cM interval indicating it was in a recombination hot spot and suitable for fine mapping. Our results demonstrate the narrowing down of initial yield QTLs by Meta-analysis and thus enabling short listing of QTLs worthy of MAS or fine mapping. The candidate genes shortlisted are useful in validating their function either by loss of function or over expression. © 2010 Springer-Verlag. Source

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