Shubranil Das’s research while affiliated with Central Agricultural University and other places

Advancements in tissue culture techniques have enabled the regeneration of a wide array of fruit varieties under in vitro condition. Use of micro-propagation technique is now available for numerous crops at a commercial scale. While this has facilitated clonal propagation and preservation of elite genotypes with superior traits, maintaining high genetic uniformity among regenerated plants remains a challenge due to the chance of induction of somaclonal variation, which results from gene mutations or changes in epigenetic marks. Such genetic variability can undermine the reliability of in vitro cloning and germplasm preservation, making it crucial to ensure the genetic fidelity of in vitro raised plants early in the process. Various strategies have been employed to assess genetic uniformity, including morphological, physiological, biochemical, cellular, and DNA-driven molecular marker methods. Despite its drawbacks, somatic variation also presents an opportunity for breeders to access new genetic diversity relatively quickly and without the need for sophisticated technology, which is especially beneficial for crops that are challenging to breed or possess limited genetic diversity. This paper examines the origins of variation triggered during the tissue culture process and investigates approaches for confirming different genetic fidelity in in vitro raised plantlets and discusses the potential applications of somaclonal variants in fruit crop improvement.

Abiotic stressorslike drought, salinity, and extreme temperatures significantly hamper global agricultural productivity by adversely affecting plant growth and crop production. As sessile organisms, plants have developed a sophisticated network of signaling pathways to recognize and address environmental challenges. At the heart of these responses are phytohormones, which play animportant role in conferring abiotic stress tolerance. The signaling pathways governed by these phytohormones are crucial for activating the physiological and molecular responses that enable plants to survive under stress conditions. Hormonal crosstalk, an integral component of the phytohormonal network, involves synergistic and antagonistic interactions that finely balance the growth-defense trade-off, allowing plants to optimize their responses to environmental stimuli. Current developments in genetics and molecular biology have shed light on the mechanisms by which phytohormonal signaling pathways are modulated during abiotic stress. This understanding opens new avenues for developing crop cultivars that are more resilient to stressthrough genetic engineering and biotechnological approaches. By manipulating hormonal pathways, it is possible to fortify plants against abiotic stresses, thus ensuring food production in the face of climate change. The present review emphasizes recent advances in understanding how phytohormones (PHs), the central regulators of plant physiological and biochemical responses, mediate plant resilience to such stresses and a strategic method to improve resistance toabiotic stressin horticultural plants, thereby helping agricultural systems remain resilient and sustainable in the face of escalating climatic challenges.

The current trend involves using in vitro regenerative methodologies to address the challenges inherent in conventional propagation techniques. Musa acuminata (AAA) cv. ‘Amrit Sagar’, indigenous to Northeast India, holds significant nutritional and biological value; nevertheless, its commercial cultivation encounters impediments such as substandard sucker quality and biotic pressures. In the present investigation, regenerated plants were initiated using male buds of M. acuminata cv. ‘Amrit Sagar’. Explants were cultured on Murashige and Skoog (MS) solid medium supplemented with varying concentrations of 6‑benzylaminopurine (BAP), thidiazuron (TDZ), and α‑naphthaleneacetic acid (NAA). The highest frequency (81.03%) of explants exhibiting white bud-like structures (WBLS) was observed in MS media enriched with TDZ (0.5 mg L⁻¹) and NAA (0.5 mg L⁻¹). Furthermore, the highest frequency (82.99%) of WBLS resulting in shoot emergence was observed in MS media enriched with TDZ (3.5 mg L⁻¹), adenine sulfate (AdS) (20 mg L⁻¹), and NAA (0.5 mg L⁻¹). The results indicated that half-strength MS media supplemented with 2.5 mg L⁻¹ indole-3-butyric acid (IBA) demonstrated superior efficacy, achieving an impressive 80.18% efficiency in root induction. A noteworthy survival rate exceeding 95% was observed for the acclimatized plants. Genetic fidelity tests using randomly amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) molecular markers indicated consistent genomic integrity in tissue-cultured plants compared to their maternal counterparts. This research outlines vital insights and optimal conditions for in vitro propagation of this banana variety.

An experiment was performed to understand the effects of aluminium toxicity (AlCl3·6H2O) on Kachai lemon growth and development. The toxic effects of aluminium were assessed for 45 days in sand media. With untreated pots serving as the control, seedlings of 1 month old were exposed to three concentrations of AlCl3·6H2O: 300 μM, 600 μM and 900 μM. The nutrient Hoagland solution was also given to seedlings along with the Aluminium (Al) treatment. The outcome demonstrated that the chlorophyll content and carotenoids declined with the increase of the concentration levels of AlCl3·6H2O and interval of treatment. The contents of O2·− (Super oxide anion), H2O2 (Hydrogen peroxide) and OH (Hydroxyl radical) in seedlings increased with the higher concentration levels of aluminium and longer exposure to Al. Additionally, the activity of the enzymes catalase, superoxide dismutase, ascorbate peroxidase, peroxidase and glutathione reductase were increased in seedlings. Different non-enzymatic antioxidants’ actions like tocopherol and Vitamin C played important defence mechanisms for the maintenance of tolerance in aluminium toxicity by increasing their content with an increase in the concentration of treatment levels in Kachai Lemon.

Jasmonates, which include jasmonic acid (JA) and methyl jasmonate (MeJA), are compounds derived from linolenic acid. In recent years, the quality and phytochemical content of various fruits have been improved using plant growth regulators both before and after harvest. They play a significant role in improving the quality and biochemical composition of different fruit crops, including fruit peel colour, accumulation of anthocyanins, phenolic compounds, and antioxidant activities in the fruit. Further, the fruit ripening process is also accelerated by the application of jasmonate as it influences different physiological and molecular mechanisms of the plant system including regulation of the activities of different hormones during the entire period of fruit growth and development starting from fruit set to till ripening, activation of genes related to ripening, etc. In the case of apples, pre-harvest application of MeJA leads to enhanced fruit coloration by stimulating the anthocyanin biosynthesis gene MdUFGluT. The concentration of JA increases significantly during the early fruit development stage but then decreases sharply, reaching its lowest level when the fruits are fully ripe which signifies its role in initiating the fruit ripening process. Jasmonates can also induce the expression of genes related to ethylene synthesis and promote the production of ethylene gas. Application of jasmonates at the pre-climacteric stage increased the expression of 1-Aminocyclopropane-1-carboxylate synthase 1 (ACS 1) and 1-Aminocyclopropane-1-Carboxylic Acid Oxidase1 (ACO 1) genes. However, the accumulation of ACS1 mRNA decreased when Propyl Dihydro Jasmonate was applied at the climacteric stage, indicating that jasmonates influence system 2 ethylene synthesis pathway. In addition, these two compounds (MeJA and JA) are safe for human consumption ; hence, can be applied at the commercial level to improve the fruit quality and ripening process in different fruit crops. This review provides an overview of the recent advancements in our understanding of the regulation of jasmonate biosynthesis, and the physiological and molecular mechanisms involved in the jasmonate-mediated fruit ripening process.

The current trend leans towards employing an in vitro-based regenerative approach to tackle the various challenges associated with conventional propagation techniques. Musa acuminata (AAA) cv. Amrit Sagar, native to North-east India, holds substantial nutritional and biological significance. However, its commercial cultivation faces obstacles such as poor sucker quality and biotic pressures. In this study, multiple shoots were obtained using shoot tip explants of M. acuminata cv. Amrit Sagar. These explants were cultured on Murashige and Skoog (MS) solid medium supplemented with varying concentrations of 6-Benzylaminopurine (BAP), adenine sulfate (AdS), and α-Naphthaleneacetic acid (NAA). To facilitate in vitro propagation, surface sterilization was optimized using 4.0% sodium hypochlorite (NaOCl) for 20 min, followed by 0.1% mercuric chloride (HgCl2) for 20 min, resulting in a contamination rate as low as 13.33%. Shoot regeneration achieved an establishment rate of 87.33% using shoot tips in MS medium with 2.5 mg L-1 BAP, 40 mg L-1 AdS, and 0.5 mg L-1 α-Naphthalene acetic acid (NAA). Optimal multiple shoot formation was observed in MS medium containing 10 mg L-1 BAP, 40 mg L-1 AdS, and 0.5 mg L-1 NAA. Regarding root development, 92.90% efficiency was noted in half-strength MS medium supplemented with 2.5 mg L-1 Indole-3-butyric acid (IBA).

Melatonin (MT), discovered as N‑acetyl-5-methoxytryptamine in 1958, exhibits significant potential as a regulator of plant growth, development and responses to environmental stressors. Its diverse levels across organs and species make it an intriguing subject for functional studies. This review explores the potential of MT, whether administered endogenously or exogenously, in mitigating various environmental stressors such as cold, metal toxicity, drought, salinity, chilling injuries, temperature fluctuations etc. A pivotal aspect of MT action involves its direct inhibition of reactive oxygen species (ROS) and reactive nitrogen species (RNS), pivotal players in oxidative stress. Mechanisms like enhanced antioxidant enzyme activity, bolstered non-enzymatic antioxidant systems, and activation of enzymes repairing oxidized proteins contribute to MT’s ability to confer resistance against abiotic stresses. Furthermore, by inducing the expression of genes related to antioxidant enzymes during stress, MT acts as a key regulator in orchestrating plant defense responses against environmental challenges. These collective actions underscore the role of MT in enhancing plant resilience to such challenges. The interaction of MT with various phytohormones in drought stress regulation prompts exploration of similar mechanisms to address diverse stressors in horticultural crops. MT’s collaborative synergy with fungicides presents a promising strategy for reducing reliance on harmful chemicals in fruit crop cultivation, thereby minimizing the environmental impact and enhancing crop management practices. However, this review also underscores the need for further research to explore how MT protects fruit crops from environmental challenges, potentially leading to environmentally friendly agricultural practices and safer food production.

Alternate bearing is one of the major concerns in majority of the commercial mango cultivars which significantly decrease the productivity as well as profitability of the crop. In mango, biochemical and physiological mechanism for flowering in alternate year is very scanty. Therefore, an effort has been made for proper understanding of biochemical and physiological basis behind on and off season flowering in mango. Four commercial mango cultivars of alternate-bearing habit viz. Bombay, Dashehari, Langra and Zardalu were selected for the investigation. Five trees under each cultivar were taken as ‘On year’ trees while another five as ‘Off year’ trees based on their bearing behavior during the previous year. The investigation was carried out for two consecutive years. Hence, the ‘On year’ tree of first year turned as ‘Off year’ tree next year and visa-vise. Physiological, biochemical, nutritional and enzymatic activity in the leaf was estimated at bud break and panicle emergence stage. Carbohydrate, protein, phenol, flavonoids and tannin contents of on-season trees had substantially higher at bud break stage (208.95 µg g− 1, 10.00 mg 100 g− 1, 4.41 mg g− 1, 28.86 mg g− 1 and 7.12 mg g− 1, respectively). At bud break stage, nitrogen, phosphorous and potassium content in leaf was recorded significantly higher (17.0, 2.50 and 6.60 g kg− 1, respectively) during off year although reverse trend was noticed for micronutrients content in the leaf. Further, off season trees had higher oxidative enzymes activity while on-season trees had a larger count of generative buds per branch (96.20). Increased physiological and biochemical activities in the leaf during bud break stage is highly responsible for panicle emergence in mango. Although, higher N, P, K content and increased oxidative enzymes activity leads to the formation of vegetative buds instead of generative one in mango while leaf’s elevated micronutrient content at the bud break stage is beneficial for the production of generative buds in mango.

Tropical fruits serve as vital pillars for health promotion, economic support, and cultural enrichment across diverse regions due to their array of flavors and nutritional advantages. This research endeavors to furnish critical insights and optimal conditions for the in vitro propagation of Rambutan (Nephelium lappaceum L.) cv. Arka Coorg Arun. Through meticulous micro propagation studies, it was observed that single nodal segments from laboratory-grown current-season seedlings and one-year-old seedlings exhibited significantly elevated survival rates at 46.67% and 43.33%, respectively. Employing carbendazim 50 WP, gentamicin, and mercuric chloride for surface sterilization led to a notable decrease in contamination rates (31.67%) alongside an augmented survival rate (61.67%). Most effective treatment in mitigating phenolic browning (10.00%) and achieving a robust survival rate (85.55%) involved ascorbic acid, 0.5% PVP, and 2% sucrose. For shoot initiation, optimal medium was identified as WPM + BAP (2 mg/L) for nodal explants from both seedling types, showcasing survival rates of 91.67% and 86.67% and a swift initiation period of 9.33 and 9.00 days, respectively. Additionally, GA3 at 2 mg/L significantly stimulated shoot elongation, yielding heightened shoot length (3.18 cm) and maximum mean shoot diameter (0.46 cm). In vitro rooting achieved its greatest success with MS + IBA (4 mg/L) + IAA (4 mg/L), demonstrating a peak rooting percentage (78.33%) and a shorter duration for root initiation (38.67 days). The subsequent hardening of rooted plantlets through transplantation into plastic cups filled with coco peat culminated in successful adaptation. These advancements not only bolster the sustainable cultivation of rambutan but also align with broader objectives, including the promotion of agricultural productivity, conservation of genetic diversity, and assurance of food security in tropical fruit-producing regions.