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Vandachostylis‘Sri-Siam’ is a fragrant orchid, suitable as a potted plant for the floriculture and perfumery industries due to its sweet citrus-like fragrance. Fragrance from the flowers was captured using SPME and subjected to GC–MS analysis. A transcriptome library was constructed from the tepals for sequencing using the Illumina MiSeq Desktop Sequencer and for de novo assembly using the CLC Genomic Workbench version 6.0. All de novo assembly sequences were subjected to bioinformatics analyses including BLASTx analysis, functional annotations and mapping of the annotated genes/gene products to the KEGG database using the Blast2go Pro software. GC–MS analysis reveals the fragrance are dominated by 68.73% monoterpenes, 11.26% esters, 4.20% sesquiterpenes and traces of alcohols (1.20%), dissimilar to both its parents. Analysis of the de novo assembly sequences generated 45,585 contigs which identified 14 fragrance-related transcripts. Information on the fragrance constituents and fragrance-related transcripts is deemed important as a reference for current and future work of using this hybrid in the breeding process of commercially valuable fragrant orchids.

This study was undertaken to evaluate growth-promoting effects of Pluronic F-68 (PF-68) on recalcitrant MR 219 rice callus. Our study shows that calli grown on Murashige and Skoog medium supplemented with 0.04% PF-68 significantly increased callus proliferation by 58.80% (fresh weight) and 23.98% (dry weight) while root formation from callus was enhanced by 28.57%. Enhanced callus proliferation was supported by biochemical analysis, whereby highest amount of soluble sugar (1.77 mg/mL) and protein (0.17 mg/mL) contents were recorded in calli grown on 0.04% PF-68. Furthermore, enhanced expression of sucrose synthase(2.65-folds) and NADH-dependent glutamate synthase(1.86-folds) genes in calli grown on 0.04% PF-68 also correlates with enhanced callus proliferation. In contrast, high concentration of PF-68 (0.10%) recorded highest amount of phenolic (0.74 mg/mL), flavonoid (0.08 mg/mL), and hydrogen peroxide content (0.06 mg/mL) as compared to other treatment groups indicates activation of plant defence mechanism towards stress. Similarly, high expression of 4-coumarate:CoA ligase 3(1.28-folds), chalcone-flavonone isomerase(1.65-folds) and ascorbate peroxidase(1.61-folds) genes were observed in calli grown on 0.10% PF-68 further supports increasing stress caused by the high concentration of PF-68. Taken together, our study revealed that optimum concentration of PF-68 could improve recalcitrant rice callus proliferation via enhanced sugar metabolism and amino acid biosynthesis which are crucial towards plant growth and development. However, at high concentration, PF-68 induces stress in plant which enhance the production of secondary metabolite to maintain cellular homeostasis.