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Extrinsic factors governing the spore encumbrance of an indigenous population of Pasteuria hyperparasitizing root-knot nematodes, Meloidogyne species.

Anju Kamra, Swapnil Pawar, Keith Davies, Sharad Mohan, ‘Extrinsic factors governing the spore encumbrance of an indigenous population of Pasteuria hyperparasitizing root-knot nematodes, Meloidogyne species’, poster presented at the European Society of Nematologists 32nd Symposium, Braga, Portugal, 28 August -2 September, 2016.Isolates of indigenous populations of gram-positive endospore-forming bacterial hyperparasite Pasteuria spp. infecting root-knot nematodes were made from arid, semi-arid, humid and sub humid ecosystems of India. A semi-arid population was successfully multiplied on cowpea (Vigna unguiculata), cv Pusa Komal under soil-less conditions in growth pouches maintained at 250C for 32±2 days. The recovery of Pasteuria infected females varied from 38.4 to 91.3% per plant. A nematode inoculum of 15 J2 per root tip with 15 spores per J2 resulted in significantly higher number of infected females than inoculum levels of 5 or 10 J2 per root tip with 10 spores/J2. Host-specificity assays with four species of root-knot showed a greater affinity of endospore attachment to M. incognita (6.25 spores per J2), followed by M. javanica (3.90), M. hapla (1.10) and M. graminicola (0.90) at a spore density of 6.9 x 105 spores per mL. Endospore attachment was not observed on infective juveniles of Heterodera cajani, H. avenae or Rotylenchulus reniformis, nor to the developmental stages of M. incognita (J3, J4 and males). A pre-exposure of spores to high temperatures (40, 45 and 500C) resulted in a progressive decline in spore attachment on M. incognita J2s with an increase in exposure period; resulting in 81.5 per cent decline on exposure at 500C, 10 minutes. Preincubation of the Pasteuria endospores with Bacillus cereus, B. subtilis and B. pumilus, followed by spore attachment assays with M. incognita J2, exhibited a per cent decline in attachment of 97.23, 94.60 and 96.5, respectively, over the untreated controls.Peer reviewe

Impact of levels of total digestible nutrients on microbiome, enzyme profile and degradation of feeds in buffalo rumen

<div><p>The present study was aimed at understanding a shift in rumen microbiome of buffaloes fed various levels of total digestible nutrients. To understand the process, the metagenomics of rumen microbes, <i>in vivo</i> and <i>in vitro</i> rumen fermentation studies were carried out. Three rumen fistulated adult male Murrah buffaloes were fed three isonitrogenous diets varying in total digestible nutrients (70, 85 and 100% of TDN requirement) in 3X3 switch over design. On dry matter basis, wheat straw/ roughage content were 81, 63 and 51% and that of maize grain was 8, 16 and 21% in three diets respectively. After 20 d of feeding, rumen liquor and rumen contents were sampled just before (0h) and 4h post feeding. <i>Ruminococcus flavefaciens</i> and <i>R</i>. <i>albus</i> (estimated with real time PCR) were higher in high roughage diets. The predominant phyla in all the three groups were Bacteroidetes, Firmicutes followed by Proteobacteria, Actinobacteria and Fibrobacteres. A core group of more than fifty rumen bacteria was present in all the animals with very little variations due to level of TDN. The most predominant bacterial genera reported in order of decreasing abundance were: <i>Prevotella</i>, <i>Bacteroides</i>, <i>Clostridium</i>, <i>Ruminococcus</i>, <i>Eubacterium</i>, <i>Parabacteroides</i>, <i>Fibrobacter</i>, <i>Butyrivibrio</i> etc. The higher diversity of the enyzmes families GH 23, GH 28, GH 39, GH 97, GH 106, and GH 127 (the enzymes active in fibre and starch degradation) were significantly higher on 100%TDN diet while CE 14 (required for the hydrolysis of bond between carbohydrate and lignin) was higher on low TDN (70%) diet, indicating ester bond cleavage was better in animals fed high roughage (wheat straw) diet.</p></div

Effect of diets varying in TDN content on VFA (mmol/dl), Ammonia nitrogen (mg/dl) and lactic acid (mg/dl) in the rumen of buffaloes.

<p>Effect of diets varying in TDN content on VFA (mmol/dl), Ammonia nitrogen (mg/dl) and lactic acid (mg/dl) in the rumen of buffaloes.</p

<i>In Vitro</i> methane production (ml/gm DDM) with rumen liquor of buffaloes fed different levels of TDN.

<p><i>In Vitro</i> methane production (ml/gm DDM) with rumen liquor of buffaloes fed different levels of TDN.</p

PCR primers for real time PCR assay with amplicon size and annealing temperature.

<p>PCR primers for real time PCR assay with amplicon size and annealing temperature.</p

Shared phyla across different treatments.

<p>Venn plot showing shared and unique phyla in rumen of buffaloes fed 70, 85 and 100% TDN. All taxa present within each group are plotted.</p

<i>In vitro</i> ammonia nitrogen (mg/dl) in different feeds incubated with rumen liquor of buffaloes fed different levels of TDN.

<p><i>In vitro</i> ammonia nitrogen (mg/dl) in different feeds incubated with rumen liquor of buffaloes fed different levels of TDN.</p