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20152
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Subject: Biotechnology and Molecular Biology × End date: 2016 × Start date: 2014 ×
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    ThesisItemOpen Access
    METAGENOMIC ANALYSIS OF GUT MICROFLORA OF FIELD AND LAB POPULATION OF TOBACCO CUTWORM (Spodoptera litura)
    (University of Agricultural Sciences, Dharwad, 2015-06) MANMOHAN KUMAR, D; PRASHANTHI, S.K.
    The insect gut harbors a variety of microorganisms that probably exceed the number of cells in insects themselves. These microorganisms can live and multiply in the insect, contributing to digestion, nutrition, and development of their host. Our study compared the bacterial communities in the larval gut of field and laboratory population of a polyphagous pest, tobacco caterpillar (Spodoptera litura) using denaturant gradient gel electrophoresis (DGGE) of amplified 16S rDNA gene sequence and by using Illumina MiSeq sequencing platform. The microbial composition of guts differed substantially among larvae collected from field and lab reared. Analysis of resulting sequence revealed that laboratory larval population harboured a relatively simple gut microflora as compared to field larval population consisting mostly Firmicutes (96.90%) and Proteabacteria (2.30%), whereas field population was diverse with having Proteobacteria (31.80%), Firmicutes (21.30%), Bacteriodetes (13.70%) and Acidobacteria (7.80%) as major genera. The lab-reared sample was rich in gram-positive species while the field sample harbors mainly Gram-negative species. DGGE results also revealed that higher bacterial diversity in the field population of larvae compared to laboratory population, interpreting the Shannon diversity index (Field H' = 2.55; Laboratory H' = 1.96) value. The simplicity of the gut bacteria community may reflect the narrower range of food available to laboratory-reared insects or other environmental factors that differ between the field and laboratory populations. Our attempts to elucidate role of gut bacteria towards suceptibilty to Bacillus thuringiensis did not give satisfactory result since the late instars of Spodoptera litura were insensitive to activity of cry toxins. Thus, understanding the composition and functional role of these gut microflora in insect growth and development will allow us to develop innovative strategies for pest management.
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    ThesisItemOpen Access
    VALIDATION OF LATE LEAF SPOT AND RUST RESISTANCE-LINKED MARKERS AND TRANSFER OF ASSOCIATED QTL TO JL 24 IN GROUNDNUT (Arachis hypogaea L.)
    (University of Agricultural Sciences Dharwad, 2015-03) SHARANABASAPPA YERI; DR. RAMESH S. BHAT
    This study was aimed at validating the markers linked to resistance for late leaf spot (LLS) and rust diseases of groundnut using Heterogeneous Inbred Family (HIF)-derived Near-Isogenic Lines (NILs), and to develop backcross lines in JL 24 using marker assisted backcross breeding (MABC) to improve foliar disease resistance. The NILs from TAG 24 × GPBD 4 and TG 26 × GPBD 4 could validate IPAHM103, GM2301 and GM1536 markers linked to LLS and rust resistance QTL. Similarly single marker analysis among Recombinant Inbreed lines (RILs) of VL 1 × 110 showed significant association of GM1009, GM2009, IPAHM103 and AhMITE1-PCR with LLS resistance at 70 DAS, but not with rust resistance. In the MABC programme, JL 24 was crossed to LLS and rust resistant variety, GPDB 4 and two interspecific derivatives, ICGV 86699 and ICGV 99005. Backcrossing and selfing resulted in the development of BC1F4, BC2F3 and BC3F3. Evaluation of these backcross generations resulted in the identification of six lines (JG4_81, JG4_43, J8-4_10, J8-4_24, J9-4_19 and J9-4_20) in BC1F4 and four lines (J8-2-3_5, J8-2-3_41, JG2-3_14 and J8-2-3_5) in BC2F3. They were resistant to LLS and rust, and showed significantly superior productivity traits over JL 24. Ten homozygous lines were identified in BC3F2. They carried resistance allele at IPAHM103, GM2301 and pPGPseq8D09 marker loci linked to LLS and rust resistance. Background selection for JG-18 from JL 24 × GPBD 4 showed 87% genome similarity to JL 24 when analysed with 30 AhTE markers that were polymorphic between JL 24 and GPBD 4. All the ten homozygous lines were comparable to JL 24 for pod and kernel features. Further, line J9-08, J8-08 and J8-11 exhibited significant superiority for productivity traits over JL 24. These backcross lines make up a useful genetic resource for the development of LLS and rust resistant lines from JL 24.