Preface Carbohydrate partitioning limits the yielding capacity of plants, thus offering a potential target for crop improvement. Grasses have the ability to buffer this source to sink interaction by transiently storing carbohydrates in stem tissue as production from the source is greater than whole-plant demand. These reserves improve yield stability by providing an alternative source when photosynthetic capacity is reduced during the later phases of grain filling, or during periods of abiotic and biotic stresses. Stem non-structural carbohydrates (NSC) translocation could be beneficial for enhancement of grain yield potential, and poor unloading into developing grains may be the possible cause of low stem NSC translocation, poor grain filling and seed formation. Moreover, when photosynthesis reductions are accelerated, leaf senescence is faster, decreasing the sucrose-starch conversion via enzymatic activity and consequently reducing the grain yield and the quality. Considering that starch represents 80-90% of final grain weight, the events involving since grain filling and final yield are associated with assimilates supplied by current photosynthesis and stem NSC remobilization capacity. Wheat is one of the main sources of calories and protein of the world’s population and therefore the pathogens that cause rust diseases of the crop are a real threat to food security. Besides the continuous evolution of rust pathogens which repeatedly results in overcoming the resistance of commercial varieties throughout the world. For instance, wheat stem rust pathogen (Puccinia graminis f. sp. tritici) evolution in east Africa (Ug99 and its variants) stripe rust (P. striiformis f. sp. tritici) fungus in parts of Africa, Asia, and Europe are a menace to food security due to their ability to spread rapidly and overcome resistance in common wheat varieties. Plant breeders are challenged by the impacts of global climatic changes. Agricultural practices will need to keep pace with the intensification of sustainable food production in order to face the challenge of feeding a world population estimated to reach about nine billion by 2050. Contemporary wheat breeding has increasingly focused on traits for improving yield potential during periods of abiotic and biotic stresses. Here, we summarize current knowledge of rust resistance, focusing on re-mobilization of non-structural carbohydrates (NSC) from leaves and stems and unloading into developing grains for yield stability of wheat.

Abstract Carbohydrates are the primary product of photosynthesis and key source of energy in plant and therefore play important role in plant growth and development. Plant carbohydrates are classified into two categories structural carbohydrates and Non-structural carbohydrates (NSCs). NSCs are main component of vegetative tissue and inside the cell they are present in plastids, cytosol, apoplast and vacuoles. Starch is the storage carbohydrate and is used in unfavorable condition on other hand soluble sugars support functions like supporting new growth and defense as they are intermediary metabolites, osmolytes, and substrates for transport. Under unfavorable condition carbon assimilation is less than the plant demand and under such condition these NSC act as “food pantry” which allow sessile plants to cope up unfavorable condition. Pattern of NSC accumulation may also differ for canopy/distal branches, stems and roots, depending on how drought has affected transport of NSC within the plant. These NSCs protect plants during desiccation and against freezing damage by stabilizing proteins complexes and membranes. Thus, NSCs are important carbohydrates for the growth and development of plant during normal as well as in stressed condition.

Abstract Carbon is the backbone for the life of all living beings. Carbohydrates are metabolic currency of plants as they provide building blocks for energy and biomass accumulation. Carbohydrates include both structural and Nonstructural carbohydrates. Structural carbohydrates like cellulose and lignin are long chain molecules for the building of plants reserves and structural support. These are main constituents of plant cell wall, stem, stalks etc. Non-structural carbohydrates (NSC) like monosaccharides, disaccharides, oligosaccharides, polysaccharides, sugar alcohols are important constituents in plants metabolism. The Non-structural carbohydrates (NSC) pool is very important for plant to meet the inadequate carbon requirement under night and stressful conditions. The quantity and distribution ratio of NSC in different tissues is an ecophysiological feature to understand the adaptive strategies of plants. Substrate for biosynthesis of NSC produced from photosynthesis. Sucrose and starch majorly involved in transport, energy metabolism, osmoregulation of plants.

Abstract Plants store structural carbohydrates (SCs) and Non-structural carbohydrates (NSCs) to buffer source–sink interactions at various phases of growth and under diverse environmental conditions. Structural carbohydrates (cellulose, lignin, hemicelluloses) provide structural integrity to the plant and the Nonstructural carbohydrates (sugars and starch) plays important role in growth, respiration, osmotic regulation, defence and helps in maintaining the carbon balance. Abiotic stresses such as drought, heat, salinity, and lodging etc. restrict the growth and development of plant which culminates into lower yield. Hence, the role of Non-structural carbohydrates needs to be elucidated for achieving desired crop improvement interventions to mitigate the harmful effects of climate change and having sturdy crop system. Improving our understanding of whole-plant sink–source dynamics and further optimising them will have far-reaching consequences in the near future.

Abstract The current photosynthesis of flag leaf is the most crucial source of assimilates that are essential for grain development in wheat. Translocation of these assimilates from the leaf to grain takes place in the form of sucrose. However, environmental cues that influence assimilate balance between the leaf and the developing grain which act as source and sink respectively determine grain yield prospects of wheat. The assimilate translocation system that links source and sink can also play a significant role. Hence, this aspect of assimilate supply has been a focus of research over the past few decades for crop improvement particularly under abiotic stress environment that tend to alter source-sink balance by impairing physiological and developmental processes in plants. Grain growth is mainly triggered when the primary assimilates meet the metabolic needs of the developing grains through the current photosynthesis or through assimilates stored in the form of Non-structural carbohydrates in stem. Hence, the improvement of photosynthetic capacity to synthesize sucrose, its storage remobilization, and utilization becomes imperative under abiotic stresses. Various aspects of Non-structural carbohydrates in wheat stem have been estimated, and efforts have been made to reveal the mechanisms of assimilate partitioning. In this context this chapter discusses strategies to improve grain yield with greater insights into the photosynthetic carbon assimilation, the pathways actively involved in the transport of sucrose from source to sink and their utilization at the sink organ. The information related to assimilate supply to the developing wheat grain under high temperature and drought stress conditions can provide opportunities to translate this knowledge into traits for improvement of climate resilience in wheat.

Abstract Global consumption of wheat during 2021/2022 marketing year reached to 787.4 million metric tons (https://www.statista.com/aboutus/our-researchcommitment/1239/m-shahbandeh). It shows about 4.4 million metric tons increase from the previous year. With the increase in population a significant increase in wheat production is needed to feed 9.7 billion mouths by 2050. A very limited effort can be directed to increase area under wheat production. Diseases and pests of wheat cause significant reduction (>30%) in production and 11-15% of total post-harvest losses of food grains were reported in India, which equates to about 20 million tonne (Basavaraja et al. 2007) and more than AUD10 million per year (Singh 2010). Thus, saving wheat from diseases can significantly contribute to the 2050 food security goal.

Abstract Wheat rusts, caused by Puccinia spp., are one of the major constraints for sustained wheat production. Significant progress has been achieved in the management of wheat rusts and understanding of wheat-Puccinia host-pathogen systems. The key research frontiers of wheat rusts research comprised disease epidemiology, the discovery of novel sources of resistance and their transfer into superior cultivars, pathogen surveillance for monitoring the virulence profiles of variants of rust pathogens, and the application of genomic technologies in cereal rust research. This chapter gives an overview of the research and development outcomes achieved to minimize the yield losses caused by wheat rusts during the last 90 years in the Indian subcontinent. Wheat rusts have been mainly controlled via genetic means; however, an integrated approach by combing the fungicides was carefully considered when needed. All efforts of managing wheat rusts in the future must cover the identification and transfer of genetically diverse rust-resistance sources with a reputation of durability into agronomically superior genotypes. The understanding of wheat rusts epidemiology globally and the region-specific virulence pattern of Puccinia spp. should be considered for gene deployment. The next-generation tools such as CRISPR-cas9 and other genome editing approaches are likely to be part of wheat rust management within a few decades.

Abstract Non-structural carbohydrates are the primary product of photosynthesis in plants. Glucose, fructose, sucrose, and so on are examples of Non-structural carbohydrates (NSC). These are free carbohydrates having a low molecular weight that are involved in the creation of structures. Plants’ principal photosynthetic product, the NSC, is involved in metabolic processes and plays a critical role in plant functional characteristics. In a recent laboratory inter-comparison, NSC concentration measurements had very minor uncertainty due to different extraction and quantification techniques. Different techniques such as High-Performance Liquid Chromatography (HPLC), Gas Chromatography-Mass Spectroscopy (GC-MS), Near Infra-red spectroscopy (NIRS), anion exchange chromatography, chemical approaches such as the Anthorn assay approach, and certain kits are used to detect NSC in plants. This review will cover the methods for measuring NSC in plant tissues and attempting to infer its dynamics, as well as how to apply these tools to go beyond simply monitoring plant carbon connections such as “how much NSC is there and where it is located” to “under what conditions and to what extent is NSC used” to support plant function.