Eastern Himalaya Research Articles

DRIS standards for identifying yield-limiting nutrients in Khasi Mandarin and their relationship with fruit yield on acidic soil of the eastern Himalayas, India

Mandarin fruits are the most widely grown citrus fruits in the world, particularly in the eastern Himalayas of India, which is the primary center of citrus diversity. Diagnosing potential nutritional imbalances using leaf tissue analysis is a mandatory practice for a higher yield. Regarding the nutritional diagnosis of Khasi mandarin plants, particularly in the acidic soil of the hilly ecology of the Eastern Himalayas, India, there is currently no information available. Therefore, the present study was conducted to identify nutrient constraints, establish leaf-based diagnostic recommended and integrated system (DRIS) norms, and determine nutrients’ relationship with fruit yields in 144 orchards. The result showed that the DRIS indices predicted a nutritional optimum value for Khasi mandarin: 2.26–2.83% N, 0.11–0.16% P, 1.86–2.07% K, 1.85–2.12% Ca, 0.33–0.48% Mg, 170.10–225.10 mg kg−1 Fe, 74.03–83.43 mg kg−1 Mn, 1.24–2.45 mg kg−1 Cu, and 19.84–21.28 mg kg−1 Zn. The DRIS norms identified the nutrients Zn, P, Ca, K, N, and Mg as deficient to low levels (14.15→2.14), while Fe, Mn, and Cu were at high to excessive levels (5.50→18.25). The nutritional balance index had a significantly negative relationship with the fruit yield. Leaf nutrient concentrations of N (0.909**), P (0.827**), K (0.867**), Zn (0.833**), Ca (0.827**), and Mg (0.592**) had a significant positive correlation with fruit yield. The finding will facilitate the correct interpretation of leaf nutrient analysis, and the norms developed will enable a precise intervention through nutrient management for higher yields in mandarin citrus.

An assessment of the geomorphodiversity and land use/cover change (LUCC) effects associated with landslides in Meghalaya, India

AbstractThe Shillong Plateau in the Eastern Himalayas is exposed to high seismicity, neo‐tectonic activity and orographic precipitation that aggravated landslides in the region by affecting hillslope processes. Landscape development is influenced by landslide phenomenon and depends upon geomorphic processes and geomorphodiversity (GmD). It is linked intimately with geomorphology, hydrology and soil type. This study uses a remote sensing and GIS‐based approach to assess the spatial linkage between GmD and landslide distribution in Meghalaya (India). GmD index (GmDI) is developed using geological, morphometric and geomorphological parameters and analysed with landslide distribution. The landslide distribution considering land use/cover change (LUCC) is also examined. The result shows that the region with high‐relief, valley and depression zone, mainly along the Dauki fault, have a high to a very high GmDI. About 61% of landslide localities are in zones of high GmDI, concentrated in the central and eastern parts of Meghalaya. Density analysis of the very high class (class 5) of GmD confirms the same. Most of these landslides occur in dense and light‐vegetated landmasses. However, the LUCC analysis reveals a significant increase in the built area on steeper slopes (average expansion ratio of 2.30 for slopes >15°) between 2017 and 2022, indicating a rising threat of landslides in urban areas of Meghalaya. The study presents the importance of GmD in active tectonic regions with particular reference to landslide potential and recent LUCC. It can aid decision‐makers in planning sustainable developments and risk mitigation strategies for landslide hazards and geoconservation.

Piper agroforestry in the Indian Himalayas: indigenous peoples’ practices, policies and incentives

BackgroundIndigenous populations across the world play a significant role in sustainable land management and conservation of biodiversity. However, indigenous agricultural practices are rarely studied in depth and remain poorly documented in many regions of the world. Documenting such practices and identifying policies and incentives that affect them can unlock their potential for better land management and biodiversity conservation.MethodsWe undertook household surveys and focus group discussions to document indigenous practices and the values of trees in Piper (Piper betle) agroforestry practiced by the ethnic Khasi (Pnar) community in the Indian Eastern Himalayas. We also undertook an in-depth vegetation sampling to quantify variations in phytosociology and tree diversity with stand age in Piper agroforestry and nearby native forests. In addition, we undertook strengths, weaknesses, opportunities and threats (SWOT) analysis and a desk review to identify policies, market support structures and incentives affecting cultivation of Piper, a cash crop of global importance.ResultsUnlike in shifting cultivation, indigenous people do not fell trees in the Piper agroforestry; instead, they allow trees to regenerate naturally and also enrich by planting tree seedlings in the gaps. Depending on the stand age, 30–49 tree species were recorded in the Piper agroforestry compared to 39 in nearby natural forests. While tree density was higher in the natural forests, greater species richness, diversity and basal area was recorded in > 25 years old Piper agroforestry stands. However, landholders do not have legally transferable or heritable rights to the land or trees.ConclusionIt is concluded that the Piper agroforestry provides a pathway for averting land degradation due to shifting cultivation, biodiversity conservation and improving livelihoods of the indigenous community. Although existing policies are supportive, Piper agroforestry is not currently benefiting from incentives and market support structures. We recommend implementation of policies, market support structures, incentives and payment for ecosystem services so that indigenous communities can benefit from the global ecosystem services they provide.

Conservation tillage and residue management practices in rice improves stress tolerance of succeeding vegetable pea by regulating physiological traits in Eastern Himalayas

The majority areas of valley lands in the Himalayan foothills remains fallow after the rice harvest. Recycling of plant biomass with conservation tillage may help in enhancing soil water availability, crop physiological function and productivity under moisture stress hill environments of this region. The present study focused on three tillage practices viz., no-till (NT), minimum tillage (MT) and conventional tillage (CT) and five nutrient management (NM) practices viz., 100 % NPK, 50 % NPK, 50 % NPK + in-situ residue retention (ISRR), 50 % NPK + weed biomass (WB) and 50 % NPK + green leaf manure (GLM) in rice and their residual effect on physio-biochemical properties, yield attributes and produce quality traits of succeeding pea varieties (Arkel and Prakash). Results revealed that total leaf chlorophyll content in vegetable pea varieties Arkel and Prakash was 12.0 and 11.5 % higher under no-till (NT) followed by 11.9 and 10.6 %, respectively under minimum tillage (MT) as compared to conventional tillage (CT) in rice. Similarly, application of 50 % NPK+ green leaf manure (GLM) and 50 % NPK+ weed biomass (WB) enhanced total leaf chlorophyll content in pea by 6.50–8.17 % and 3.93–5.48 % for pea varieties Arkel and Prakash, respectively. Photosynthetic rate and leaf dry weight were found 40.4 and 80.2 % higher under MT in Arkel whereas transpiration rate (E) and shoot dry matter were 33.1 and 19.3 % higher in Prakash under MT. Leaf water potential and root-to-shoot ratio were found 22.6 and 16.5 % higher in Prakash under MT and NT compared to CT respectively. Leaf temperature and stomatal conductance were 8.67 % lower and 9.8 % higher under MT in Prakash respectively as compared to CT, whereas 4.8 and 13.0 % higher under 50 % NPK +GLM and 50 % NPK+WB as compared 100 % NPK. Leaf cell viability was 22.5 and 20.1 % higher under MT whereas leaf MDA content was 29.9 and 28.3 % higher under MT in Arkel and Prakash respectively. Leaf relative water content was significantly higher to the tune of 25.7 and 22.4 % under NT compared to CT whereas leaf cell membrane integrity was 41.3 and 40.4 % higher under NT for Arkel and Prakash. Higher pod protein was noticed under MT along with 50 % NPK+GLM (13.1 %), whereas total soluble sugar was recorded highest under NT with 50 % NPK+GLM (21.1 %) in Prakash and MT with 50 % NPK+GLM (18.3 %) in Arkel. However, in both varieties, lower TSS was recorded under CT and with 50 % NPK (14.2 and 11.2 %) and the reducing sugar was maximum under the application of 50 % NPK+WB as compared to 100 % NPK alone. For both varieties of pea, green pod yield was recorded highest under MT (4.76 & 5.89 t/ha) as compared to CT (4.76 & 6.17 t/ha) and NT (4.76 & 5.55 t/ha). While 50 % NPK+WB has recorded significantly highest green pod yield of Arkel, 50 % NPK+ GLM has caused the highest yield of Prakash. PCA executed on physiological traits explained the total variability to the tune of 85.50 %, thereby extracting three PC's viz., PC 1 (62.63 %), 12.58 %) and 10.28 %, respectively. Thus, the adoption of MT in rice followed by NT in winter pea with the application of 50 % NPK+WB or 50 % NPK+GLM is promising for better physiological traits and subsequently favoring the grain yield of pea under stressful hill environments of Eastern Himalaya.

Human‐associated genetic landscape of walnuts in the Himalaya: implications for conservation and utilization

AbstractAimsA comprehensive understanding of the genetic variation of walnuts (Juglans regia and J. sigillata) in the Himalaya and its potential drivers are essential for the conservation and sustainable utilization of these plant genetic resources. In this study, we aimed to uncover the genetic landscape of walnuts and potential drivers in the Himalaya for better utilization, awareness, sustainable management and conservation of the extant genetic resources of walnuts in the vast Himalayan landscape.LocationThe Himalaya biodiversity hotspot.MethodsA total of 1410 wild or feral walnut trees from 65 populations of J. regia and J. sigillata across four countries in the Himalaya were collected. The genetic diversity, population structure, hybridization and gene flow were thoroughly investigated based on the chloroplast genome and 31 nuclear microsatellite markers. The patterns and drivers of the walnut genetic landscape were further explored.ResultsWe detected three genetic groups of J. regia (JR1, JR2, JR3), one of J. sigillata (JS) and two hybrid types (JR1 × JS and JR3 × JS) of walnut in the Himalaya, with the western Himalaya identified as the genetic diversity hotspot of J. regia. The spatial genetic pattern of the J. regia was significantly influenced by geographic and climatic factors. Human‐mediated dispersal probably promoted the hybridization and gene introgression between J. regia and J. sigillata, which reshaped the genetic landscape of walnut populations in the Himalaya.Main ConclusionsThe extant genetic landscape of walnuts in the Himalaya was driven by natural and anthropogenic forces. Regarding conservation, the western and eastern Himalaya are the genetic reservoir of J. regia and J. sigillata, and hence, pure individuals should be urgently protected from frequent hybridization and introgression. In addition, we propose the utilization of natural hybrid resources coupled with new breeding techniques that combine genomic and phenotypic data.

Assessing climate change and its impact on kiwi (Actinidia deliciosa Chev.) production in the Eastern Himalayan Region of India through a combined approach of people perception and meteorological data

Assessing climate change and its impact on kiwi (Actinidia deliciosa Chev.) production in the Eastern Himalayan Region of India through a combined approach of people perception and meteorological data

Silk Road to the contact zone: protestant movement in the Eastern Himalaya

Silk Road to the contact zone: protestant movement in the Eastern Himalaya

Assessing the Activity of Eastern Himalayan Extensional Structures: Evidence from Low-Temperature Thermochronology of Granitic Rocks from Yadong

The east–west-trending South Tibetan Detachment System (STDS) and north–south-trending rifts (NSTRs) are the two main types of extensional structures that have developed within the Tibetan Plateau during continent–continent collision since the early Cenozoic. They have played significant roles in the evolution of the plateau, but it is unclear how they are related genetically. In the Yadong area of the eastern Himalaya, the NSTRs cross-cut the STDS. Apatite and zircon fission track ages of a leucogranite pluton in the footwall of the two extensional faults can be used to reconstruct the cooling and exhumation history and thereby constrain the activity of extensional structures. The new AFT ages range from 10.96 ± 0.70 to 5.68 ± 0.37 Ma, and the ZFT age is 13.57 ± 0.61 Ma. Track length distributions are unimodal, albeit negatively skewed, with standard deviations between 1.4 and 2.1 µm and mean track lengths between 11.6 and 13.4 µm. In conjunction with previously published datasets, the thermal history of the region is best explained by three distinct pulses of exhumation in the last 16 Ma. The first pulse (16–12 Ma) records a brittle slip on the STDS. The two subsequent pulses are attributed to the movement on the Yadong normal fault. The normal fault initiated at ~12 Ma and experienced a pulse of accelerated exhumation between 6.2 and 4.7 Ma, probably reflecting the occurrence of two distinct phases of fault activity within the NSTRs, which were primarily instigated by slab tear of the subducting Indian plate.

Human-induced impacts on ecological infrastructure in the Himalayan urban agglomerations

The spatial dimensions of urban ecological services (UESs) transformation and population density in major Himalayan urban agglomerations (UAs) were analyzed to deduce the impacts of anthropogenic activities in recent decades (1991–2018). The multi-satellite-based study exhibited a remarkable increase (193 sq. km; 15%) in the built infrastructure and a significant decline (−24%) in the ecological infrastructure in the Himalayan UAs. The continuous anthropogenic influence on the Himalayan ecosystems in the last three decades has created severe socio-economic-ecological consequences that have largely impacted green infrastructure (GI), which is receptive to conversion to built infrastructure. The large-scale UES alteration was evident within larger cities in the western and central Himalayas, in contrast to the low transformation in Eastern Himalayan cities barring Shimla UA. The investigation highlights the rapid and haphazard population influx and urban growth that imposed a higher risk of natural hazards in the Eastern and Central Himalayan UAs and necessitated suitable policies to build an ecologically sustainable urban ecosystem.

Enhanced light absorption by ambient brown carbon aerosols in the eastern Himalayas

This study investigates the light absorption properties of organic aerosols in PM10 collected at a high-altitude location (2700 m a.s.l.) in the eastern Himalayas from March 2019 to February 2020.

Unraveling the Sensitivity and Response of Ecosystems to Rising Moisture Stress in India

Moisture stress has increased substantially across the globe with significant impact on terrestrial ecosystems. Therefore, we examine the sensitivity and response of terrestrial ecosystems to rising moisture stress in India during recent decades (2000 to 2019). The Random Forest approach reveals that soil moisture (SM) is the major driver (31%) of ecosystem functioning and its health in India. Moisture availability in the atmosphere (Vapor Pressure Deficit [VPD], 25.8%) and on land (Climatic Water Deficit [CWD], 24.6%) also have major control on the ecosystem functioning. Terrestrial warming (1.8%) increases evapotranspiration (ET, 10.76%), depletes SM (2.45%), and rises CWD (3.37%) and VPD (1.8%), despite the increase in precipitation (P, 2.54%) in recent decade (2010 to 2019) as compared to previous decade (2000 to 2009). In response to the rising moisture stress, the Water Use Efficiency (WUE) is increasing in the eastern Indo-Gangetic Plain (IGP), Southern India (SI), and eastern Himalaya, but the Carbon Use Efficiency (CUE) is decreasing in these regions. The Resilience method reveals that IGP and Northwest are nonresilient to moisture stress in terms of CUE, whereas SI, the western Central India, eastern Himalaya, and Northeast are nonresilient in terms of WUE. Our results reveal that ecosystem functioning factors (CUE and WUE) are increasing (decreasing) in regions where they are nonresilient (resilient) to moisture stress. Therefore, there is a need of proper ecosystem planning, climate risk management and policies to mitigate the threats of climate change and food security by maintaining ecosystem resilience to moisture stress across the regions.

Cassiterite of the Kuqu spodumene-bearing pegmatites in the eastern Himalaya, Tibet, and its implication

Cassiterite of the Kuqu spodumene-bearing pegmatites in the eastern Himalaya, Tibet, and its implication

Elemental and boron isotopic variations of tourmalines from the Miocene leucogranite-pegmatite in Kuju, eastern Himalaya: Implications for the evolution of magmatic melts

Elemental and boron isotopic variations of tourmalines from the Miocene leucogranite-pegmatite in Kuju, eastern Himalaya: Implications for the evolution of magmatic melts

First Report of Leaf Spot Caused by Corynespora cassiicola on Jasminum sambac in Pakistan.

Jasminum sambac L. is a species of jasmine native to a small region in the eastern Himalayas and is cultivated worldwide as an ornamental plant (USDA-ARS 2016). In Pakistan, it is cultivated for ornamental purposes throughout the country. The flowers of this plant are traditionally used in the preparation of essential oils and for making jasmine tea. The flowers and leaves also have been used in folk medicine to treat breast cancer, epilepsy, ulcers and promote wound healing (Al-Snafi 2018). In December, 2017, almost 10 leaves of 3 plants of J. sambac growing plant nursery of Gehlan, Pattoki, Punjab a province of Pakistan were observed with leaf spot disease. Infected leaves exhibited circular to sub-circular spots with indistinct margins and grey papery centers delimited by dark brown rims. For further microscopic study, the infected leaves were examined under a stereomicroscope. For the isolation and cultural studies of infecting fungus, infected parts of leaves were surface sterilized in 1% NaOCl for about 10 seconds, washed twice in sterilized distilled water, plated on potato dextrose agar (PDA) medium and incubated at 25°C for 4 days. Pure cultures were obtained having colonies of light to dark brown color. Conidia (n=20) were light brown to pale olivaceous brown, smooth, obclavate to cylindrical in shape, 99.5-118.5 μm in length and 12.5-15.0 μm in width, with mostly 3 to 14 pseudosepta. Conidiophores (n=20) were straight to slightly curved, unbranched, and pale to light brown in color. Based on the morphological characteristics of the colonies and conidiophores and conidia, the pathogen was identified as Corynespora cassiicola (Berk and M.A. Curtis) C.T. Wei. (Berkeley & Curtis 1968; Lu et al. 2021; Wei 1950). Genomic DNA was extracted following using modified CTAB method (Gardes and Bruns 1993) and internal transcribed spacer (ITS) region was amplified with ITS1 and ITS4 primers (White et al. 1990). The ITS sequence generated of about 553 bp and deposited in GenBank (accession no. MN954556), was found more than 99% similar to previously deposited sequences of C. cassiicola (GenBank accession nos. MN339671, EU364535, FJ852574, MK139711, EU131374) as verified through BLASTn and phylogenetic tree construction. A pathogenicity test was performed for fulfilling Koch'spostulates. Conidial suspension (105 conidia/ml) of the recovered isolate was sprayed on the 5 healthy leaves of 2-month-old seedling of J. sambac. Mock inoculated plants sprayed sterile distilled water were used as a control. The seedlings were covered with plastic bags to maintain high humidity at 24 to 28°C for a week. Identical disease symptoms to those observed in nursery plants were observed on the leaves of the inoculated plants in 7 days but not mock inoculated plants and results were reconfirmed. The reoccurred fungus was isolated from the diseased spots of the inoculated leaves to complete Koch's postulates and identified microscopically. A representative sample of leaves with lesions was deposited in the LAH herbarium, Department of Botany University of the Punjab, Pakistan (LAH35691). Previously, C. cassicola has been found infecting Jasminum mesnyi in China and Jasminum sp. in Florida (Alfieri et al. 1984; Zhang et al. 2018). The best of our knowledge, this is the first report of leaf spot caused by C. cassiicola on J. sambac in Pakistan. It will establish a foundation for future studies of management strategies for this plant disease caused by C. cassiicola.

The old man by the waterfall: deep entanglements of culture, state-making and geopolitics in Arunachal Pradesh

Arunachal Pradesh, a state in Northeast India, is going through a phase of rapid infrastructural expansion, a phenomenon intensified due to the state’s geostrategic location. Despite the colonial enterprise of frontier-making and the resulting securitisation of space, the presence of the eastern Himalayan frontier has historically infused the region with elements of both steadfastness and dynamism, as its spatial fluidity persists in one form or the other. Meanwhile, despite being situated in a Himalayan corridor, the region finds itself entangled in the contentious politics in which states in South and Southeast Asia are locked. Drawing on ethnographic experiences from two geopolitically sensitive and spatially significant places, Menchukha and Namsai, situated on the eastern Himalayan slopes at Arunachal Pradesh, this article discusses the paradoxical conditions of ‘selective permeability’ (Popescu 2015: 50) that often informs contemporary border regimes, where factors favouring cross-border mobility are weighed against the demands of maintaining territorial integrity. In this context, this article looks at some prominent sites of pilgrimage and religious tourism to understand the differential attention they receive from the state, revealing a complex assemblage of spatial dynamics, cultural logics and geostrategic rationales that operate in geopolitically charged borderlands.

Two-decadal climate impacts on growth of major forest types of Eastern Himalaya

Forests affect regional climates, livelihoods and global cycles of water, carbon and nitrogen. Anthropogenic activities and climatic change affect forest health and national growth. Therefore, developing effective forest management plans requires understanding of the drivers of forest growth. The primary objective of this study was to understand the long-term effect of abiotic factors on the growth of forests in the region. This study used Moderate Resolution Imaging Spectroradiometer (MODIS) data for vegetation indices like NDVI and EVI and NASA's Land Assimilation datasets (wind speed, evapotranspiration, soil moisture and temperature) to understand their role on forest growth through statistical techniques such as Pearson's correlation and Multiple Linear Regression. The study examined the relationship between standard monthly vegetation indices and abiotic variables (i.e., moisture and temperature at different soil profiles up to 2 m depth, land surface temperature, evapotranspiration, relative humidity, wind velocity, and air temperature at 2 m height) in selected forests of the Eastern Himalayas for two decades (2001–2020, n = 240). Rainfall, temperature, and other associated factors significantly affected forest growth in the region. It was observed that rainfall alone affected forest growth in the region. However, its impact was maximum after two months of the rain events, reflecting a significant lag effect. Soil moisture at different depths affected vegetation growth in all forest types. Reduced soil moisture had a more significant effect on old-growth forests than younger forests. Multiple Linear Regression models developed with the abiotic factors explained higher variability in forest growth. In conclusion, this study reveals that rainfall, temperature, and their associated variables significantly affected forest growth in the study area. The study has significant implications for forest management in the region for formulating better strategies to mitigate climate change effects on forests in the region in future.

Dietary Iodine Intake and Pattern of Thyroid Disorders among the Ethnic Population of Eastern Himalayan Ranges of India

Background and Aim: In the present study, dietary iodine intake and thyroid functioning were assessed among the ethnic adolescent group of Eastern Himalayan range with the hypothesis that insufficient iodine intake negatively affects normal thyroid functions. The aim of the study was to see the prevalence and relation between iodine deficiency and thyroid functioning. Materials and Methods: It is a hospital-based study conducted in the health care facilities of Dima Hasao district, Assam, from April 2021 to March 2022. The study included 821 subjects including both male and female of adolescent age group (10–19 years). The thyroid profiling, anti-Thyroid peroxidase antibody (anti-TPO Ab), and urinary iodine content (UIC) were carried out. Thyroid hormone analysis was carried out by chemiluminescence assay. The anti-TPO Ab was determined using the electrochemiluminescence immunoassay analyzer. The dietary iodine intake was measured on the basis of UIC and was determined by arsenic cerium catalytic spectrophotometry method by the Sandell-Kolthoff reaction. Results: The prevalence of thyroid disorder among the studied population was found to be 13.8%. Among different conditions of thyroid disorders, hypothyroidism was present in 10.6% and hyperthyroidism in 3.13%. 4.18% had elevated anti-TPO Ab. Among the euthyroid subjects with different thyroid disorders, 1.48% and 21% had anti-TPO Ab positivity, respectively. The median UIC was 99.97 µg/l. 25.78% of the population had iodine deficiency. Thyroid disorders were common in subjects with iodine deficiency (61.34%) than iodine sufficient subjects (20%). Conclusion: The work was an attempt to demonstrate how the dietary iodine intake influences thyroid functioning among the adolescent ethnic population of Eastern Himalayas which is manifested as high prevalence of subclinical hypothyroidism with iodine deficiency. The work underscores region specific recommendation on iodine supplementation for populations living in geographically remote locations.

Conceptualization, Characterization and Establishment of Model Large Cardamom Village in Eastern Himalaya of West Bengal

The farmers’ livelihood in the Himalayan region of West Bengal mainly depends on large cardamom cultivation. However, the farmers in the region were continuously facing low yield, high disease incidence, and poor quality of large cardamom. An alternative extension approach namely ‘Model Large Cardamom Village’ was conceptualized to address these issues in Tindhurey village of Kalimpong in West Bengal. Diverse scientific technologies and practices were promoted in the adopted village from 2018 to 2022. An outcome-based impact evaluation was done in 2023 with a sample of 350 farmers. The maximum yield increment was observed in the Seremna cultivar (45.94%) followed by Bharlangey (42.86%), Ramsai (40%), and Golsey cultivar (36.67%). Similarly, the maximum increase in income was reported in the Seremna cultivar from Rs. 160000/ha. to Rs. 290000/ha. Other significant impact of Model Large Cardamom Village was increased adoption of recommended technologies, the decline in pest and disease incidence, enhanced social networking, the decline in migration of youth from the village, increased access to different production inputs and services, and starting large cardamom-based tourism. The study shows the potential of a specific and focused extension approach to address the technological gap at the regional level.

Phylogenetic study of some major Dendrobium species of Eastern Himalaya using internal transcribed spacer marker

The entire internal transcribed spacer (ITS) region sequencing was used to determine the phylogenetic relationship of 44 Eastern Himalayan Dendrobium species using the Sanger method and MEGA 11. The combined length of ITS-I and ITS-II varies between 623 and 644 base pairs (bp). Among them, there are 403 polymorphic, 91 unique, and 223 conserved nucleotides. In addition, 337 nucleotides are parsimony informative, with a mean of 0.51 that supports the presence of genetic variation in the genome of the selected species. Overall composition distance is 0.32, transition and transversion bias (R) 1.444, and mean evolutionary divergence (d) 0.16. The length of ITS-2 sequences is bigger than that of ITS-I. ITS-II exhibits a higher G+C% content, and the K2+G model is the most suitable, with the lowest penalty for nucleotide substitutions. The average consistency, retention, composite value, and parsimony-informative sites (in parentheses) are 0.5028 (0.4571), 0.6545 (0.6545), and 0.3290 (0.2992), respectively. The mean value of the disparity indices is 0.192, which measures the variation in evolutionary trends between two sequences. In addition, the ratio of non-synonymous to synonymous substitutions (dN/dS) is −0.33 promotes purifying species selection. The prevalence of the TGT codon is abundant across the sequences, with the UCG codon exhibiting the highest relative synonymous codon usage (RSCU). Conversely, the GAC codon has the lowest RSCU value. The greatest genetic divergence occurred between Dendrobium aphyllum and Dendrobium denudans. The Breviflorus species group has the most genetic diversity, whereas Formosae has the least. Between Grastidium and Stachyobium group sequences had the highest evolutionary distance, whereas Dendrobium and Grastidium had the least. The negative value of Tajima’s D, Fu and Li’s D*, F*, and Fu’s Fs tests indicated current population is growing after facing a recent bottleneck. This study suggests that ITS sequencing could be a major focus of comparative sequencing at the generic level in Dendrobium plants and could provide valuable phylogenetic reconstruction for clarifying the evolutionary relevance of the taxa studied.

Molecular, morphological, and biomolecular characterization of ethyl methanesulfonate-induced mutations in Aerides odoratum, an orchid

Aerides odoratum L. is a medicinal and ornamental orchid of the Eastern Himalayas, India. Its uses in pharmacology are nought because of its rare occurrence, longer life cycle, and lack of artificial methods for large-scale propagation. Protocorms (60 days old) were treated with various concentrations of ethyl methanesulfonate ranging from 0.025% to 0.5% for different durations (2, 5, 7, and 10 days) during M0 (treatment) in vitro generation. The survival of these protocorms and the generation of shoots and roots were noted. 10–20 plantlets of each treatment showing variation in the number and weight of shoots in M0 generation (treatment generation) were maintained for three subsequent generations. M3 (third generation) axenic plantlets were hardened in the orchidarium with a 75% survival frequency. Four mutant lines (M3V1–M3V4) were established based on RAPD analysis of the leaf DNA of 300-day-old plants. M3V-1 was noted as the best among all mutant lines based on morphological analysis, whereas M3V-2 was noted as the most superior in terms of having the highest quantity of osmolytes, pigments, stomata, and phenol. M3V-3 had maximum root length, leaf breadth, and carotenoids. M3V-4 showed the viridis chlorophyll spectrum as the most distinguishing factor. Hence, this standardized protocol can be used for the genetic improvement of A. odoratum.