No abstract

No abstract

This study examined the effects of Stimplex™, a marine plant extract formulation from Ascophyllum nodosum, on some common cucumber fungal pathogens. Greenhouse cucumber plants were sprayed and/or root drenched using Stimplex™ at 0.5% or 1% concentration twice at 10-day intervals. Treatments also included application of fungicide (chlorothalonil, 2 g L −1 ) alternating with Stimplex™ application. Treated plants were inoculated with four cucumber fungal pathogens including Alternaria cucumerinum, Didymella applanata, Fusarium oxysporum, and Botrytis cinerea. Stimplex™ application resulted in a significant reduction in disease incidence of all the pathogens tested. The disease control effect was greater for Alternaria and Fusarium infection, followed by Didymella and Botrytis. Combined spray and root drenching with Stimplex™ was more effective than either spray or root drenching alone. The alternation of one fungicide application, alternated with Stimplex™ application, was highly effective and found to be the best treatment in reducing the disease ratings. Plants treated with Stimplex™ showed enhanced activities of various defenserelated enzymes including chitinase, β-1,3-glucanase, peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, and lipoxygenase. Altered transcript levels of various defense genes, including chitinase, lipoxygenase, glucanase, peroxidase, and phenylalanine ammonia lyase were observed in treated plants. Cucumber plants treated with Stimplex™ also accumulated higher level of phenolics compared to water controls. These results suggest that seaweed extracts enhance disease resistance in cucumber probably through induction of defense genes or enzymes.

No abstract

The effects of Ascophyllum nodosum marine-plant extracts on 'Thompson seedless' grape (Vitis vinifera L.) production and yield variables was studied from 2002-04. Performed in cooperation with a commercial orchard near Selma, California, the randomized complete block design used five replicates and examined several experimental products and several standard Ascophyllum treatments (ATAN 0029). Given the preliminary nature of the experimental products, only the Ascophyllum treatments are discussed. Dose rates for the Ascophyllum treatments varied from 1 to 2 L/ha whereas the number of applications ranged from 4 to 8 applications per treated plot. Over this 3-year period, Ascophyllum extracts consistently outperformed the controls (regular crop management program) and produced better quality fruit and higher yields. Results in 2002 indicate increases in berries per bunch, berry size, rachis length and the number of primary bunches per plant with 4 and 8 applications of 2 L/ha. Treated fruit also performed better in storage than control fruit. In 2003, there was an increase of at least 58.4% in both grade #1 and #2 fruit, an increase of 7.7% in average berry size and 26.5% in berry weight in response to 4 or 8 applications at 2 L/ha. In 2004, yields for treated plots were again greater than the controls (60.4%), due in part, to increases in berry weight (38.8%) and size (12.4%). Overall, increases in grower return-on-investment (ROI) were realized in each of the three years. The beneficial impact of these extracts is thought to be associated with compounds that may include, but are not limited to the betaines, oligosaccharides, polyamines, cytokinins and/or other hormones. Fractionation chemistry research is currently underway on Ascophyllum extracts in order to identify individual or specific active ingredients. These fractions will then be examined in a series of closely monitored bioassays before being further tested on 'Thompson' seedless grapes.

Ascophyllum nodosum extract (ANE) contains bioactive compounds that improve the growth of Arabidopsis in experimentally-induced saline conditions; however, the molecular mechanisms through which ANE elicits tolerance to salinity remain largely unexplored. Micro RNAs (miRNAs) are key regulators of gene expression, playing crucial roles in plant growth, development, and stress tolerance. Next generation sequencing of miRNAs from leaves of control Arabidopsis and from plants subjected to three treatments (ANE, NaCl and ANE+NaCl) was used to identify ANE-responsive miRNA in the absence and presence of saline conditions. Differential gene expression analysis revealed that ANE had a strong effect on miRNAs expression in both conditions. In the presence of salinity, ANE tended to reduce the up-regulation or the down-regulation trend induced caused by NaCl in miRNAs such as ath-miR396a-5p, ath-miR399, ath-miR2111b and ath-miR827. To further uncover the effects of ANE, the expression of several target genes of a number of ANE-responsive miRNAs was analyzed by qPCR. NaCl, but not ANE, down-regulated miR396a-5p, which negatively regulated the expression of AtGRF7 leading to a higher expression of AtDREB2a and AtRD29 in the presence of ANE+NaCl, as compared to ANE alone. ANE+NaCl initially reduced and then enhanced the expression of ath-miR169g-5p, while the expression of the target genes AtNFYA1 and ATNFYA2, known to be involved in the salinity tolerance mechanism, was increased as compared to ANE or to NaCl treatments. ANE and ANE+NaCl modified the expression of ath-miR399, ath-miR827, ath-miR2111b, and their target genes AtUBC24, AtWAK2, AtSYG1 and At3g27150, suggesting a role of ANE in phosphate homeostasis. In vivo and in vitro experiments confirmed the improved growth of Arabidopsis in presence of ANE, in saline conditions and in phosphate-deprived medium, further substantiating the influence of ANE on a variety of essential physiological processes in Arabidopsis including salinity tolerance and phosphate uptake.

No abstract

Summary Seaweeds have been used as a source of natural fertilizer and biostimulant in agriculture for centuries. However, their effects on soil and crop root microbiota remain unclear. Here, we used a commercially available Ascophyllum nodosum extract (ANE) to test its effect on bacterial and fungal communities of rhizospheric soils and roots of pepper and tomato plants in greenhouse trials. Two independent trials were conducted in a split‐block design. We used amplicon sequencing targeting fungal ITS and bacterial 16S rRNA gene to determine microbial community structure changes. We find that productivity parameters of root, shoot and fruit biomass were positively and significantly influenced by the ANE amendment. In addition, a‐diversity differed significantly between amended and control plants, but only in some of the experimental conditions. Species composition among sites (b‐diversity) differed according to the amendment treatment in all four communities (fungal‐root, fungal‐soil, bacterial‐root and bacterial‐soil). Finally, we identified a number of candidate taxa most strongly correlated with crop yield increases. Further studies on isolation and characterization of these microbial taxa linked to the application of liquid seaweed extract may help to enhance crop yield in sustainable agro‐ecosystems.