Sanatsujat Singh’s research while affiliated with Institute of Himalayan Bioresource Technology and other places

Dendranthema grandiflora is an important cut flower with high economic importance in the floriculture industry. Identification of stable and high yielding genotypes of Dendranthema grandiflora, hence becomes paramount for ensuring its year-round production. In this context, the genotype by environment interaction effects on 22 chrysanthemum hybrids across six test environments were investigated. The experiment was conducted using Randomized Complete Block Design with three replications for 6 years and data on various agro-morphological and yield-contributing traits were evaluated. Our analysis revealed significant mean sum of squares due to environmental, genotypic and genotype by environment interaction variations for all examined traits. A 2D GGE biplot constructed using first two principal components computed as 59.2% and 23.3% of the differences in genotype by environment interaction for flower yield per plant. The GGE biplot identified two top-performing genotypes, G2 and G5, while the AMMI model highlighted genotypes G17, G15, G6, G5, and G2 as the best performers. Genotype G17 ranked highest for multiple traits, while G2 displayed high mean flower yield as well as stability across all environments. According to AEC line, genotypes G2 and G5 exhibited exceptional stability, whereas genotypes G4, G18 and G19 demonstrated lower stability but maintained high average flower yields. Hence, our findings provide valuable insights into chrysanthemum hybrids that were not only best performing but also hold promise to meet the growers demand of the cut flower industry and can be recommended for large scale commercial cultivation.

Considering the major source of plant-derived low/non-calorie steviol glycosides (SGs), comprehensive physiological, biochemical, and deep transcriptional investigations were conducted to explicit deeper insight into multiple abiotic stress responses in Stevia rebaudiana. The physiological indicators including photosynthesis, chlorophyll, relative water content, shoot growth, electrolyte leakage, and SG biosynthesis were negatively impacted under drought (DS), followed by salinity (SS) and waterlogging (WS). Global transcriptional analysis revealed significant upregulated expression of the genes encoding for ROS detoxification (GST, SOD, APX, glutathione peroxidase), osmotic adjustment (alpha-trehalose-phosphate and S-adenosylmethionine decarboxylase), ion transporters (CAX, NHX, CNGS, VPPase, VATPase), water channel (PIP1, TIP) and abiotic stress-responsive candidate genes (LEA, HSPs, and Dehydrins) regulating abiotic stress response in S. rebaudiana. These inferences were complemented with predicted interactome network that revealed regulation of energy metabolism by key stress-responsive genes (GST, HKT1, MAPKs, P5CSs, PIP), transcription factors (HSFA2, DREB1A, DREB2A), and abiotic stress responsive pathways (ABA, ethylene, ion stress). This is the first detailed study to comprehend the molecular regulation of stress response and their interplay under DS, SS, and WS. The key genes and regulators can be functionally validated, and will facilitate targeted gene editing for genetic improvement of crop sustainability under changing environmental conditions in S. rebaudiana.

Stevia rebaudiana, a native of South America, is a perennial herb of the Asteraceae family, also known as a natural sweetener due to the presence of steviol glycosides (SGs) in the leaves. China is the largest producer and exporter of stevia, while Japan is the primary consumer. The increasing demand for natural low-calorie sweeteners in the medicine and food industry has increased the pressure over stevia cultivation. Still, its cultivation and region-specific agrotechnologies need to be developed. The major bottleneck in stevia production are the lack of region specific cultivation technologies, non-availability of quality planting material, and uncharacterized and not properly conserved plant genetic resources. All these constraints have limited the stevia production to some specific regions of the world. Development of high-yielding cultivars with enhanced SGs content using modern breeding techniques is of prime importance to meet its increasing demand. Among the glycosides present in the leaves, rebaudioside-A is the most desirable glycosides having 250-300 times sweeter than sucrose, while, after bitter taste is due to the presence of stevioside and dulcoside. Therefore, the development of varieties with high rebaudioside-A and low stevioside content is highly desirable. This chapter focused on the improvement of propagation methods, characterization and conservation of genetic resource in stevia and its utilization in crop improvement programs.

Plant-specific GRAS transcription factors (TFs) are reported to play an essential role in regulating several biological processes, such as plant growth and development, phytochrome signal, arbuscular mycorrhiza symbiosis, stress responses. However, rose GRAS genes are still unexplored. In this study, 59 rose GRAS genes (RcGRAS) were identified and were grouped into 17 subfamilies. Gene structure analyses showed that most of the RcGRAS genes were intronless and were relatively conserved. Gene expression analysis in various tissues (leaf, stem and flower bud) identified the tissue-specific expression of GRAS genes. For instance, RcGRAS30 (SCL3) and RcGRAS9 (HAM) got > 20 fold and > 5 folds upregulated in stem as comparison to leaf, and suggested their possible involvement in different growth and development processes. Further, significant difference in expression of GRAS genes in response to exogenous gibberellin (GA) and drought stress alluded the potential functions of these genes in hormone and stress responses. In summary, a comprehensive exploration of the rose GRAS gene family was performed and also their possible role in growth, development, stress and hormonal response were depicted. These basic insights can be utilized for further functional characterization-based studies on GRAS genes.

Wild marigold has a growing demand for its essential oil in the flavor and fragrance industries. It can be grown over a broad range of climates, but the changing climatic conditions lead to abiotic stresses, thus restricting its productivity. Abiotic stresses at elevated levels result in the reduction of germination, growth, and essential oil quality of wild marigold leading to heterogeneous and inferior grades of “Tagetes oil.” Drought, salinity, and heavy metal stress at elevated levels have common effects in terms of ROS formation, which are the major cause of growth deterioration in wild marigold. Temperatures above 35°C inhibit seed germination. Irradiance stress reduces the biomass and essential oil yield. Waterlogging adversely affects the survival of wild marigold in high rainfall regions. The application of plant nutrients (fertilizers) modulates the biomass and essential oil yield. Wild marigold employs multiple tolerance mechanisms to cope up with the adverse effects of abiotic stresses such as the increased activity of antioxidants to maintain cellular redox homeostasis, enhanced lipid peroxidation in the cell membrane to maintain cell wall architecture, production of secondary metabolites, and accumulation of osmolytes. In this review, we tried to understand how abiotic stresses affect wild marigold. Understanding the physiological changes and biochemical characteristics of stress tolerance will contribute to the development of stress-tolerant lines of wild marigold.

German chamomile (M. chamomilla) is recognized as a star herb due to its medicinal and aromatic properties. This plant is found across a wide range of climatic and soil conditions. Both the flower heads and blue essential oils of German chamomile possess several pharmacological properties of an anti-inflammatory, antimicrobial, antiseptic, antispasmodic and sedative, etc., nature, which makes it a highly sought after herb for use in many pharma and aroma industries. Chamomile tea, prepared from its flower heads, is also a well-known herbal tea for mind and body relaxation. Though it is a high-demand herb, farmers have not adopted this plant for large scale cultivation as a crop, which could improve their livelihood, due to the high cost in flower heads harvesting, loss in over mature and immature flower heads picking during harvesting, unavailability of varieties and agrotechnologies for machine harvesting, a lack of efficient process development of oil extraction and in the lack of improved stable varieties. There are many studies that have reported on the phytochemistry and pharmacological uses of chamomile, which further explore its importance in the medicine industry. Several studies are also present in the literature on its cultivation practices and plant ecology. However, studies on breeding behavior, genetic improvement, varietal development and mechanical harvesting are scarce in German chamomile. Hence, keeping in mind various aspects of farmers’ and researchers’ interest, earlier reports on taxonomy, floral biology, processing of oil extraction, active constituents, uses, agronomy, breeding challenges and opportunities in German chamomile are summarized in this review.

Palmarosa [Cymbopogon martinii (Roxb.) W. Watson] is an economically crucial aromatic grass species commercially cultivated for its essential oil. The essential oil has high demand in cosmetics, tobacco products, and perfumery industries. The present study investigates the inflorescence development of palmarosa into ten distinct stages. Light microscopy and morphological observations led to identifying these stages. The pollen is monoporate and spherical in shape (22–32 μm) that is available from the first inflorescence development stage. The stigma becomes receptive at stage - 5. The inflorescence development stage - 6 indicates the highest pollen availability as well as viability. The florets are small lacking sepal and petals, suggesting an anemophilous mechanism of pollination. The open-pollination conditions are best suitable for a good seed set than self-pollinated conditions. The floral biology of palmarosa suggested cross-pollination breeding behavior. Scanning electron microscopy of leaves reveals the presence of essential oil glands (120–145 μm) responsible for its essential oil's rose-like aroma. The analysis of essential oil through gas chromatography-mass spectrometry revealed considerable variations of metabolites in the leaves, inflorescence, and whole plant (excluding roots). Multivariate clustering of oil data showed that the amount of geraniol increases towards maturity. In contrast, the amount of neryl acetate was observed highest at immature stages, and it decreases towards mature inflorescence stages.

Valeriana jatamansi Jones (Syn. V. wallichii DC.) is an aromatic, medicinal herb used as a tranquilizer and in treating sleep disorders. Rhizome is mainly used to extract essential oil (EO) and valepotriates. High quality and economic yield of rhizomes are available in the third year of growth. Therefore, the cultivation of V. jatamansi is not picking up, and over-exploitation of this plant from wild habitats to meet the increasing demand of the pharmaceutical industry is the cause of threat to the genetic diversity of the species. Further, collections from the wild are heterogeneous, resulting in variable produce. The development of clonal lines can ensure uniform quality and yield of rhizome biomass. An effective clonal propagation method was standardized using different hormonal concentrations of naphthalene acetic acid (NAA) on apical shoot cuttings from the selected clone CSIR-IHBT-VJ-05 for different time durations and raised over various planting media. NAA treatment of 50 ppm concentration for 30 min was found optimum for root induction in apical shoots of V. jatamansi. Variations for EO composition within the clone were non-significant, while samples of the control population were variable. The best quality EO (patchouli alcohol ∼62%) was available during the third year of plant growth. A propagation technique for large-scale quality plant material (QPM) production has been standardized to reduce the stress over natural resources and promote V. jatamansi for use in the aromatic and pharmaceutical industry.