Fumigant and contact toxicities of individual and additive combinations of biorational-essential oils for control of rice weevil (Sitophilus oryzae).

Fumigant and contact activity of individual and combination of EOs (cumin seed and black pepper oil) were conducted against rice weevil (Sitophilus oryzae). Cumin seed and black pepper oil individually exhibited 100% insecticidal activity (Contact and Fumigant) against S. oryzae at 24 and 168 h of exposure in the absence and presence of food, respectively. Overall, differential insect mortality rates were observed with individual EOs; however, cumin seed EO showed higher insecticidal activity in both fumigant and contact bioassays than black pepper EO. Binary mixtures of cumin seed and black pepper oil at 60:40 and 80:20 ratios showed higher toxicity than individual EOs against S. oryzae and further, additive interaction of binary combinations of EOs resulted in complete insecticidal activity of S. oryzae. Thus, we conclude binary mixtures of cumin seed and black pepper EOs might be a promising prophylactic treatment solution for control of S. oryzae to prevent stored grain infestation.

Vulnerability of Soil Microbiome to Monocropping of Medicinal and Aromatic Plants and Its Restoration Through Intercropping and Organic Amendments.

Cultivation of medicinal and aromatic plants (MAPs) is persistently increasing due to excessive demands of naturals. Agricultural land and its microbial diversity are primarily adapted to conventional crops, and introduction of MAP and their continuous monocropping may disturb the ecological stability of soil microbiome. Here, the effect of cultivation of MAPs on soil microbial diversity was studied. The aim of the study is to examine the effects of cultivation of MAPs on the possible shift in soil microbial diversity and to restore such impacts by using organic amendments or intercropping. Terminal restriction fragments polymorphism (TRFLP) and next-generation sequencing (NGS) studies showed that of the various selected MAPs, maximal modulation in the soil microbial diversity patterns was noticed in fields of Mentha arvensis and Artemisia annua, and the traces of essential oil/phytochemicals were detected in bulk and rhizospheric soil. In both Artemisia- and Mentha-cultivated soil, the total operating taxonomic unit (OTU) declined in both bulk and rhizospheric soil in comparison to control (Zea mays), but the bacterial richness of Mentha soil was slightly higher than that of control. However, cultivation of Mentha improved the evenness of the microbial community. The inclusion of crops like Sesbania and Chlorophytum and the application of vermicompost (VC) enhanced the microbial richness and evenness, thereby restoring the soil microbial state shift and resulting in higher productivity in the continuously Mentha cropped field. Our study concludes that long-term cultivation of some MAPs may affect the richness but promote the evenness of microbial diversity. The state shift could be restored to some extent, and crop productivity could be enhanced by the inclusion of selected crops and organic manures in cropping systems.

Fungal endophytes attune withanolide biosynthesis in Withania somnifera, prime to enhanced withanolide A content in leaves and roots.

Endophytes have been reported from all plant species from different parts of tissue including root, stem and leaves. Here we report, three fungal endophytes, Aspergillus terreus strain 2aWF (2aWF), Penicillium oxalicum strain 5aWF (5aWF), and Sarocladium kiliense strain 10aWF (10aWF) from Withania somnifera, which could enhance withanolides content in leaf and root. Upon treatment with the above endophytes to 4 weeks old plants in field conditions, W. somnifera elicited withanolide A content (97 to 100%) in leaves without considerable changes in withaferin A content. Furthermore, withanolide A content in roots of 5aWF and 10aWF endophyte treated W. somnifera plants increased up to 52% and 65% respectively. Incidentally, expression profile of withanolide and sterol biosynthetic pathway genes HMGR, DXR, FPPS, SQS, SQE, CAS, SMT1, STE1 and CYP710A1 were significantly upregulated in 2aWF, 5aWF and 10aWF fungal endophyte treated plants. Besides, modulation of withanolide biosynthetic pathway genes, fungal endophytes also induce a host resistant related gene, NPR1 resulting in 2, 4 and 16 fold expression levels in 2aWF, 10aWF and 5aWF endophyte treatments respectively, compared to control plants. Overall, our results illustrate that application of native-fungal endophytes 2aWF (96.60%), 5aWF (95%) and 10aWF (147%) enhances plant biomass in addition to withanolide content.

Endophytes of Withania somnifera modulate in planta content and the site of withanolide biosynthesis.

Tissue specific biosynthesis of secondary metabolites is a distinguished feature of medicinal plants. Withania somnifera, source of pharmaceutically important withanolides biosynthesizes withaferin-A in leaves and withanolide-A in roots. To increase the in planta withanolides production, a sustainable approach needs to be explored. Here, we isolated endophytes from different parts of W. somnifera plants and their promising role in in planta withanolide biosynthesis was established in both in-vivo grown as well in in-vitro raised composite W. somnifera plants. Overall, the fungal endophytes improved photosynthesis, plant growth and biomass, and the root-associated bacterial endophytes enhanced the withanolide content in both in-vivo and in-vitro grown plants by modulating the expression of withanolide biosynthesis genes in leaves and roots. Surprisingly, a few indole-3-acetic acid (IAA)-producing and nitrogen-fixing root-associated endophytes could induce the biosynthesis of withaferin-A in roots by inducing in planta IAA-production and upregulating the expression of withanolide biosynthesis genes especially MEP-pathway genes (DXS and DXR) in roots as well. Results indicate the role of endophytes in modulating the synthesis and site of withanolides production and the selected endophytes can be used for enhancing the in planta withanolide production and enriching roots with pharmaceutically important withaferin-A which is generally absent in roots.

Fungal endophytes of Catharanthus roseus enhance vindoline content by modulating structural and regulatory genes related to terpenoid indole alkaloid biosynthesis.

Not much is known about the mechanism of endophyte-mediated induction of secondary metabolite production in Catharanthus roseus. In the present study two fungal endophytes, Curvularia sp. CATDLF5 and Choanephora infundibulifera CATDLF6 were isolated from the leaves of the plant that were found to enhance vindoline content by 229-403%. The isolated endophytes did not affect the primary metabolism of the plant as the maximum quantum efficiency of PSII, net CO2 assimilation, plant biomass and starch content of endophyte-inoculated plants was similar to endophyte-free control plants. Expression of terpenoid indole alkaloid (TIA) pathway genes, geraniol 10-hydroxylase (G10H), tryptophan decarboxylase (TDC), strictosidine synthase (STR), 16-hydoxytabersonine-O-methyltransferase (16OMT), desacetoxyvindoline-4-hydroxylase (D4H), deacetylvindoline-4-O-acetyltransferase (DAT) were upregulated in endophyte-inoculated plants. Endophyte inoculation upregulated the expression of the gene for transcriptional activator octadecanoid-responsive Catharanthus AP2-domain protein (ORCA3) and downregulated the expression of Cys2/His2-type zinc finger protein family transcriptional repressors (ZCTs). The gene for the vacuolar class III peroxidase (PRX1), responsible for coupling vindoline and catharanthine, was upregulated in endophyte-inoculated plants. These endophytes may enhance vindoline production by modulating the expression of key structural and regulatory genes of vindoline biosynthesis without affecting the primary metabolism of the host plant.

Endophytes of opium poppy differentially modulate host plant productivity and genes for the biosynthetic pathway of benzylisoquinoline alkaloids.

MAIN CONCLUSION: Endophytes reside in different parts of the poppy plant and perform the tissue-specific functions. Most leaf endophytes modulate photosynthetic efficiency, plant growth, and productivity while capsule endophytes modulate alkaloid biosynthesis. Endophytes promote plant growth, provide protection from environmental stresses and are the source of important secondary metabolites. Here, we established that the endophytes of opium poppy Papaver somniferum L. may play a role in the modulation of plant productivity and benzylisoquinoline alkaloid (BIA) biosynthesis. A total of 22 endophytes isolated from leaves, roots, capsules and seeds of the poppy plants were identified. Isolated endophytes were used to inoculate the endophytes free poppy seeds and screened for their ability to improve plant productivity and BIA production. It was evident that the endophytes from leaf were involved in improving photosynthetic efficiency, and thus crop growth and yield and the endophytes from capsule were involved in enhancing BIA biosynthesis. Capsule endophytes of alkaloid-rich P. somniferum cv. Sampada enhanced BIA production even in alkaloid-less cv. Sujata. Expression study of the genes involved in BIA biosynthesis conferred the differential regulation of their expression in the presence of capsule endophytes. The capsule endophyte SM1B (Acinetobacter) upregulated the expression of the key genes for the BIA biosynthesis except thebaine 6-O-demethylase (T6ODM) and codeine O-demethylase (CODM). On the other hand, another capsule endophyte SM3B (Marmoricola sp.) could upregulate both T6ODM and CODM. Colonization of poppy plant by endophytes isolated from leaves, roots and capsules found to be higher in their respective plant parts confirmed their tissue-specific role. Overall, the results demonstrate the specific role of endophytes in the modulation of host plant productivity and BIA production.