Puneet Walia

Fifty-nine diverse Brassica juncea (Indian mustard) genotypes were used to find an effective screening method to identify salt tolerance at the germination and seedling stages. Salinity stress limits crop productivity and is difficult to simulate on farms, hindering parental selection for hybridization programmes and the development of tolerant cultivars. To estimate an optimum salt concentration for screening, seeds of 15 genotypes were selected randomly and grown in vitro at 0 mM/L, 75 mM/L, 150 mM/L, 225 mM/L, and 300 mM/L concentrations of NaCl in 2 replications in a complete randomized design. Various morphological parameters, viz., length of seedling, root and shoot length, fresh weight, and dry weight, were observed to determine a single concentration using the Salt Injury Index. Then, this optimum concentration (225 mM/L) was used to assess the salt tolerance of all the 59 genotypes in 4 replications while observing the same morphological parameters. With the help of Mean Membership Function Value evaluation criteria, the genotypes were categorized into 5 grades: 4 highly salt-tolerant (HST), 6 salt-tolerant (ST), 19 moderately salt-tolerant (MST), 21 salt-sensitive (SS), and 9 highly salt-sensitive (HSS). Seedling fresh weight (SFW) at 225 mM/L was found to be an ideal trait, which demonstrates the extent to which B. juncea genotypes respond to saline conditions. This is the first report that establishes a highly efficient and reliable method for evaluating the salinity tolerance of Indian mustard at the seedling stage and will facilitate breeders in the development of salt-tolerant cultivars.

Indian mustard, a member of the Brassicaceae family, is a cool-season crop cultivated extensively in various agro-ecological conditions, contributing significantly to vegetable oilseed production. However, being a thermosensitive and C3 plant [1], Indian mustard is highly susceptible to high-temperature stress, particularly during critical developmental stages [2]. High temperatures disrupt physiological, morphological, and biochemical mechanisms essential for plant growth and development. From altered chlorophyll content and osmotic water potential to impaired photosynthesis and reduced seed oil accumulation, heat stress detrimentally affects various aspects of Indian mustard physiology. This comprehensive review examines the impacts of heat stress on Indian mustard, a significant oilseed crop, and explores adaptation strategies to mitigate its adverse effects. Additionally, heat stress during reproductive stages leads to flower abortion, reduced fertility, and poor seed development, significantly impacting yield potential. To cope with heat stress, plant response mechanisms involve intricate signaling pathways, leading to cellular readjustments at transcriptome, epigenome, proteome, and metabolome levels. Breeding approaches, including conventional techniques and advanced molecular tools like CRISPR/Cas-based genome editing, offer promising avenues for developing heat-tolerant cultivars. Integration of multi-omics approaches aids in identifying stress-responsive genes and metabolic pathways crucial for adaptation. Agronomic strategies, such as nutrient management and microbial inoculation, play vital roles in mitigating heat stress effects and enhancing plant resilience. Collaborative efforts and interdisciplinary research are essential to deepen our understanding of heat stress responses and develop sustainable solutions to ensure oilseed crop productivity and food security in the face of climate change. This review underscores the urgency of addressing heat stress challenges in Indian mustard cultivation and highlights the need for concerted efforts to develop effective adaptation strategies for sustainable agriculture.

The global demand for food is rising due to population growth, climate change, and evolving consumer preferences. Traditional plant breeding programs typically require a decade or more to develop and release new crop varieties. Speed breeding is a cutting-edge technique designed to expedite genetic improvement by significantly reducing the seed-to-seed cycle. This review explores the principles, applications, and potential of this method in accelerating agricultural advancement. Originating from NASA's experiments for food production in space, the approach has evolved into a highly efficient strategy for speeding up breeding cycles in cereal crops. By manipulating light, photoperiodic regimes, temperature, and humidity within controlled environments, it is possible to achieve up to six generations of photo-insensitive crops and two to three generations of other crops per year. This rapid generation turnover provides a unique opportunity for accelerated genetic mapping, trait stacking, and enhanced genomic selection. Speed breeding complements modern breeding technologies such as genome editing, high-throughput genotyping, and CRISPR, facilitating quicker development of crop varieties with improved traits. Its applications extend to boosting transgenic pipelines and understanding critical physiological traits in crops. Furthermore, it aligns with breeding methods like single plant selection and single seed descent, offering a more efficient path to desirable outcomes. However, challenges remain, including the need for specialized infrastructure, the impact of genotypic variations, and potential stress responses due to accelerated conditions. Despite these hurdles, speed breeding represents a promising tool in the quest for food security and resilient agricultural systems. This review examines its potential to transform plant breeding, reduce cultivar development times, and contribute to rapid agricultural advancement in a changing world.

Heterosis, the phenomenon where hybrid offspring exhibit superior traits compared to their inbred parents, has captivated scientists for decades due to its immense potential for crop improvement. Unravelling the molecular basis of heterosis has remained a challenge, but recent advancements in genomic and molecular techniques have shed new light on this intriguing phenomenon. This review paper provides a comprehensive overview of the current understanding of the molecular mechanisms underlying heterosis. We delve into the intricate interplay of genetic factors and regulatory networks that contribute to the manifestation of heterosis. Genomic studies have revealed structural variations, such as rearrangements and copy number variations, which may play a crucial role in hybrid vigour. Furthermore, we explore the dynamic nature of gene expression patterns during hybridization, highlighting the activation of novel gene networks and the modulation of epigenetic mechanisms. Transcriptomic analyses have identified key genes and pathways associated with heterosis, shedding light on the intricate molecular interactions that drive the superior performance of hybrids. Additionally, we discuss the emerging role of small RNAs, transcription factors, and regulatory elements in orchestrating heterosis. These molecular players act as conductors in the genetic symphony of hybrid vigour, fine-tuning gene expression and facilitating the coordinated functioning of diverse biological processes. Understanding the molecular basis of heterosis holds immense promise for crop improvement and sustainable agriculture. By leveraging this knowledge, breeders can harness the full potential of hybrid breeding to develop high-yielding and resilient crop varieties. This review aims to inspire further research and collaboration in unravelling the mysteries of heterosis, paving the way for innovative strategies to enhance global food security and agricultural productivity.