Microbial biofilm inoculants benefit growth and yield of chrysanthemum varieties under protected cultivation through enhanced nutrient availability

<p>Protected cultivation of ornamental flowers, as a commercial venture, becomes less profitable with excessive use of fertilizers. The present study examined the influence of microbial biofilm inoculants (<i>Anabaena</i>–<i>Azotobacter, Anabaena</i>–<i>Trichoderma</i> and <i>Trichoderma</i>–<i>Azotobacter</i>) on the availability of soil nutrients and structure of rhizosphere microbial communities in three varieties of chrysanthemum (var. White Star, Thai Chen Queen and Zembla). Varietal-specific responses in growth, enzyme activities, flower yield of plants and availability of soil nutrients were recorded. Dehydrogenase activity was highest in var. White Star treated with the <i>Anabaena</i>–<i>Trichoderma</i> biofilm inoculants. The <i>Anabaena</i>–<i>Azotobacter</i> inoculant enhanced the availability of nitrogen, phosphorus and micronutrients in the soil, besides 40–50% increase in soil organic carbon, as compared to carrier alone or no inoculation. PCR-DGGE profiling of the cyanobacterial communities and qPCR quantification of 16S rRNA abundance of bacteria, archaea and cyanobacteria in the rhizosphere soils, revealed the stronger influences of these inoculants, especially in var. Zembla. Principal Component Analysis (PCA) helped to illustrate that the enhanced microbe-mediated availability of soil macro-and micronutrients, except iron content (Fe), was the most influential factor facilitating improved plant growth and yield parameters. The <i>Anabaena</i>–<i>Azotobacter</i>, and <i>Anabaena–Trichoderma</i> biofilm inoculants, proved superior in all three chrysanthemum varieties.</p

Evaluation of 19,460 Wheat Accessions Conserved in the Indian National Genebank to Identify New Sources of Resistance to Rust and Spot Blotch Diseases

<div><p>A comprehensive germplasm evaluation study of wheat accessions conserved in the Indian National Genebank was conducted to identify sources of rust and spot blotch resistance. Genebank accessions comprising three species of wheat–<i>Triticum aestivum</i>, <i>T</i>. <i>durum</i> and <i>T</i>. <i>dicoccum</i> were screened sequentially at multiple disease hotspots, during the 2011–14 crop seasons, carrying only resistant accessions to the next step of evaluation. Wheat accessions which were found to be resistant in the field were then assayed for seedling resistance and profiled using molecular markers. In the primary evaluation, 19,460 accessions were screened at Wellington (Tamil Nadu), a hotspot for wheat rusts. We identified 4925 accessions to be resistant and these were further evaluated at Gurdaspur (Punjab), a hotspot for stripe rust and at Cooch Behar (West Bengal), a hotspot for spot blotch. The second round evaluation identified 498 accessions potentially resistant to multiple rusts and 868 accessions potentially resistant to spot blotch. Evaluation of rust resistant accessions for seedling resistance against seven virulent pathotypes of three rusts under artificial epiphytotic conditions identified 137 accessions potentially resistant to multiple rusts. Molecular analysis to identify different combinations of genetic loci imparting resistance to leaf rust, stem rust, stripe rust and spot blotch using linked molecular markers, identified 45 wheat accessions containing known resistance genes against all three rusts as well as a QTL for spot blotch resistance. The resistant germplasm accessions, particularly against stripe rust, identified in this study can be excellent potential candidates to be employed for breeding resistance into the background of high yielding wheat cultivars through conventional or molecular breeding approaches, and are expected to contribute toward food security at national and global levels.</p></div

Diversity among rust resistant genotypes based on profiles of linked molecular markers.

<p>Diversity among rust resistant genotypes based on profiles of linked molecular markers.</p

Seedling resistance in wheat accessions.

<p>These genebank accessions were identified as resistant in the primary field evaluation at the hotspots. The seedling resistance was recorded as resistant either to only one rust disease (leaf, stem or stripe) or a combination of two or all the three rust diseases. Seedling resistance screening was carried out under controlled condition at the Regional Station of Indian Institute of Wheat and Barley Research (IIWBR), Flowerdale, Shimla. Accession-wise details are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167702#pone.0167702.s003" target="_blank">S3 Table</a>.</p

Amplicon profile of 137 wheat accessions for SSR marker G<i>wm427</i> linked to <i>Sr13</i>. M = 100bp ladder.

<p>Amplicon profile of 137 wheat accessions for SSR marker G<i>wm427</i> linked to <i>Sr13</i>. M = 100bp ladder.</p

Gene combinations present in 137 wheat accessions.

<p>These wheat accessions were screened for the amplification of markers linked to five <i>Lr</i> genes, three <i>Sr</i> genes, four <i>Yr</i> genes and one spot blotch resistance QTL. Disease reaction recorded at Gurdaspur for yellow rust and at Cooch Behar for spot blotch are also given. R- resistant; MR- Moderately resistant; MS- moderately susceptible, S- susceptible and #N/A—no data.</p

Locations of evaluation experiments of wheat germplasm against rusts and spot blotch.

<p>Primary screening against the three rusts was carried out at Wellington. Subsequent screening for stripe rust resistance was done at Gurdaspur and for spot blotch resistance at Cooch Behar. The seedling resistance assay was carried out at Flowerdale and molecular profiling was done at New Delhi. Base map was generated using DIVA-GIS data (<a href="http://www.diva-gis.org/gdata" target="_blank">www.diva-gis.org/gdata</a>).</p

Results of primary screening of wheat germplasm against three rusts.

<p>Stem: Stem rust; Leaf: Leaf rust; Stripe: Stripe rust S: Susceptible; MS: Moderately susceptible; MR: Moderately resistant; R: Resistant.</p

Experimental layout, flow of germplasm and salient results of the study.

<p>Blue filled boxes denote germplasm at various stages of the experiment. Trapezoids denote screening (green for field evaluation and red for lab assay). Figures and tables containing details corresponding to each stage of the flow are mentioned in italics below boxes.</p

Summary of evaluation of 4925 wheat accessions carried out at Gurdaspur for stripe rust and Cooch Behar for spot blotch.

<p>Summary of evaluation of 4925 wheat accessions carried out at Gurdaspur for stripe rust and Cooch Behar for spot blotch.</p