Plant Breeding for Nutritional Security: Enhancing Animal and Human Health

INTRODUCTION

Over two billion humans are undergoing hidden hunger, a term employed to represent the insufficiency of micronutrients, although over one billion individuals are malnourished as a consequence of a lack of food (Kennedy et al., 2003). Certainly, 20 mineral elements, 13 vitamins, 9 amino acids, and 2 fatty acids are mandatory for an individual’s health (Graham et al., 2007). Vitamin A, iron, and zinc are among the major causes of diseases and sickness in impoverished countries, and micronutrient malnutrition is predominant in emerging countries (WHO, 2002). The diet of a few individuals may also be deficient in various minerals like copper, magnesium, selenium, and calcium (Stein, 2010). Agriculture serves as the major source of nutrients needed by farm animals and individuals. Cereal or tuber-origin foods fulfill the calorie demands but lack the essential micronutrients, which are utilized by two-thirds of the world’s population as a diet. While the main objective of contemporary agriculture has been to boost yields at a lessened cost, with a nominal attention to the nutritional quality (Sands et al., 2009).

Malnutrition of micronutrients imposes a significant health-related issues globally (Bouis et al., 2011), with nearly two-thirds of the inhabitants at risk of lacking in more than one essential nutrient (Stein, 2010). These deficiencies are specifically dominant in children and among breastfeeding women, particularly in developing countries, where it promote susceptibility to diseases and inhibit the physical and mental development (WHO, 2005). Major determining components involve infant and poor maternal nutrition, limited access to fortified foods, improper food preparation, insufficient breastfeeding, and a lack of dietary variety.

Biofortification is an eco-friendly and cost-efficient technique to deal with undernourishment (Bouis et al., 2011), especially for rural areas in solitude or low-rainfall regions with restricted access to fortified food or diverse diets (Saltzman et al., 2013). Through genetic mechanisms and marker-assisted selection (MAS), plant-breeding strategies can increase the nutritional availability of staple crops, providing an eco-friendly and affordable approach to enhance global nutrition (Bouis, 2000). Malnutrition prevails as a major issue for researchers and policymakers in developing countries, where agriculture is the dominant occupation. For resolving the micronutrient deficiency, Biofortifying staple crops like millet, rice, sorghum, maize and wheat exhibit a major role. Escalating the genetic quality of crops, especially for zinc (Zn) and iron (Fe) amount in grains, not only increase grain productivity but also improves their nutritional contents.

NUTRITIONAL CONTENTS OF FOOD AND FORAGE CROPS

Bio-accessibility of micronutrients in leafy vegetables is impacted by their pectin content, with excess micronutrient bio-accessibility present in condensed tannins like drumstick tree. Establishing cultivars having minimum pectin content can enhance the absorption of micronutrients in the human gut. Vegetables and fruits involve in more than 40% of total food waste and losses (Lipinski et al., 2013), thus R&D investments in processing, storage, and distribution techniques can minimize these. Creating drying technologies and extracting by-products may also decrease the food wastage (Salim et al., 2017). Dealing with low consumption and encouraging healthier food choices, like dietary guidelines, is necessary. School and vegetable home gardens can also bolster supply and demand (Schreinemachers et al., 2018).

Forage crops, also termed as bulky feeds, are derived from cereal, legume, and cereal cropping. They might be nourished straightly to animal livestock or processed into hay or dry biomass. Concentrates are commonly oilseed, legume seeds, cereal, or co-products of their production for biofuel, textile, and people food. They may also involve more energy feedstuffs like fats of animal origin and sugar-enrich crop molasses. For human consumption, the preparation of these feeds can surpass the plant-origin food in industrialized countries (Krausmann et al., 2008). The diets of livestock could be solely forage or majorly forage with concentrate additions. Concentrate enrichment is employed to recompense for nutritive shortages in the supply of forage, improve animal performance, or within a difficult time like calving (Erb et al., 2012). Forage crops can be grown in mixed species cultivation to supply environmental and nutritive advantages. Such as, the alfalfa, the greatest-yielding perennial forage legume, can be cultivated solely or in combination with several grass species (Bélanger et al., 2006).

Digestibility

The nutritional status of forage crop relies on the ratios and concentration of carbohydrates, lipids, and proteins. The digestibility (D-value) of every crop estimates the amount of energy derived by animal. Forage crop generally involves 50-80% carbohydrates, with the addition of supplement if the percentage is very low. Basic types of carbohydrates involve cellulose and hemicellulose, which are broken down into simple sugars by glycosidic bonds. Various ratios of carbohydrates can impact downstream digestibility, particularly if structure of cell wall limits digestion or cell wall penetration (Weimer, 1996). Lignin, a polyphenolic compound, influences the digestibility of cellulose hemicellulose through binding with cell wall proteins and structural carbohydrates. High sugar and low lignin content gave rise to high digestibility in major forage crops like grasses, like Lolium perenne (Ruckle et al., 2017).

Protein

Availability of nitrogen to farm animals is mainly from forage proteins, with the mostly form being Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) (Wallace et al., 1997). Protein digestibility is influenced by lignin and micronutrients like condensed tannins or proanthocyanidins. Liquid N can lead to bloat, however very high tannin content can cause to the loss of nutritional value and unabsorbed protein (Piluzza et al., 2014). All grasses involve low or no proanthocyanidins, whereas legumes such as Sericea lespedeza and big trefoil exhibit levels as above to 18% DM (Mueller‐Harvey, 2006).

Lipids

Forage crops involve polyunsaturated fatty acids (PUFAs) ranging from 10-30 g kg-1 (Hatfield et al., 2007), with linolenic acid being the highly prevalent (Clapham et al., 2005).These dietary lipids are essential for the quality of animal items, as forage diets having reduced PUFA contents can provide leaner meat (Elswyk & McNeill, 2014). Fresh forages exhibit to provide milk having decreased PUFA level and enhance trans-fatty acids (Chilliard et al., 2007).

Trace Elements

Trace element and minerals from forages are necessary for the health of livestock, particularly as the utilization of antibiotic reduces. Zinc is crucial for the defense system, and it can be consumed in feed as supplement. However, its abundance can lead to waste excretion (Brugger & Windisch, 2015). Building up of toxic minerals is beneficial but in low level as high level could be toxic (Zhu et al., 2009).

Biomass Production

Nutritional quality of forage crop relies on the quick biomass production, that can be influenced by extensive growth and species. To assess yield, ground area cover and plant height are vital element (Freeman et al., 2007). Capability of shoot meristem to cue to enhanced growth in post-cutting is necessary. Some species of forage have enhanced root exudation (Paterson & Sim, 1999), which promotes rhizosphere microbes, transporting soil nutrients for regrowth. Sustaining a maximum nutrient and supply of water is essential for the production of forage biomass, with supply of nitrogen being critical for re-grow in after trimming grass and alfalfa’s regrowth capacity (Meuriot et al., 2005).

HEALTH RISKS DUE TO NUTRITIONAL MALNUTRITION

The significance and the impact of some micronutrients on human and animal development includes; Iron is an essential micronutrient necessary for making the structure of body, supporting proteins, muscle tissue and the development of the central nervous system. The deficiency of iron is the highly dominant form of malnutrition around the world, influencing nearly one-third of the population, with 80% sufferer from developing countries (Boccio & Iyengar, 2003). The major cause of iron deficiency involves blood loss, insufficient dietary iron intake and increased needs due to illness (Skalicky et al., 2006). This situation causes serious outcomes, like increased mortality and morbidity rates, decreased labor productivity and decreased cognitive function (Grant et al., 2002).

Zinc is a necessary mineral which exhibits a key role in more than 200 enzymes, giving the immune system functionality, DNA synthesis, and wound healing. It is vital for normal development, growth and the sense of smell and taste. Its deficiency is a prominent cause of fatalities among children below 5, reporting for about 450,000 deaths yearly. This insufficiency can lead to the reproductive issues, stunted growth, cognitive delays, gastrointestinal disturbances, impaired or reduced immune function and delayed sexual development (Black et al., 2008). The main cause of zinc deficiency is insufficient dietary intake, specifically in communities with decrease levels of absorbable zinc and with minimal approach to bioavailable sources like meat (Cakmak, 2008). Iodine is a vital nutrient that promotes the proper functioning of the thyroid glands, metabolic processes and hormone synthesis. Its deficiency can lead to the hypothyroidism, developmental delays or mental retardation and thyroid enlargement (Taylor et al., 2014). Its deficiency causing goiter which found in 187 million people worldwide as per 2010, representing 2.7% of the population. It leads to 2,700 deaths in 2013 up from 2,100 deaths in 1990 (Vos et al., 2012). Utilizing iodine-rich products in the diet is an efficient practice for reducing and preventing iodine deficiency. Foliate also referred as vitamin B9, which is a water-soluble vitamin necessary for maintenance and cell production, specifically during the period of rapid cell growth. It contributes a crucial role in the synthesis of DNA and also cause anemia in adults. It is naturally abundant in legumes, fruit, and leafy green vegetables. Its insufficient intake can reduce growth in infants and children.

Anti-nutritional elements are often found in forage crops like pearl millet, sorghum, and oats that can harms animal health and in severe cases, led to livestock mortalities. These damaging compounds include nitrates, phytic acids, tannins, hydrogen cyanide (HCN), and oxalates, all of them can degrade the crop quality (Keeler et al., 2013). Nitrates are commonly found in forage crops like sorghum, oats, pearl millet, and maize, besides C4 forages being the essential nitrate accumulator. Plants absorbs nitrogen in the form of nitrate, then by enzymatic activity converted into amino acid (Crawford, 1995). The risk of nitrate build up is heightened by heavy nitrogen fertilizers, particularly within the last stages of crop growth and under abiotic stress condition (Salvagiotti et al., 2009). Intake of nitrate can lead into bloodstream, where hemoglobin transforms into methemoglobin, causing potential toxicity in forage crops.

IMPROVING FORAGE AND FOOD CROPS

Plant Breeding for Enhancement of Mineral Elements

Harvest Plus is a conventional breeding program that aims to improve basic foods like rice, beans, cassava, sweet potatoes, and wheat across Africa and Asia. The aim of this program is to discover seeds with high mineral content and induce them into cultivars that have been adapted regionally. Relying on the mineral and crop, targets of mineral improvement might range from 33-100%. The progress of crop improvement programs consists on the heritability of desirable traits and the extent of genetic variability. To apply successful selection pressure, genetic variability of breeding material is necessary. Correlation studies are beneficial for comprehension of the contribution of numerous traits to the yield of grain, enabling for the choose and recognizing of superior plants. Genetic variability analysis gives perception into the degree of variation in a population, with the variation from phenotypic traits show phenotypic variance while variance in genetic makeup reflects genotypic variance. The proportion of inherited variation can be determined by the estimation of heritability, while on their own, it do not predict the genetic progress gained by choosing superior individuals.

The evolutionary background of crop plants and a comprehension of genetic diversity promotes the considerable advancement in crop improvement. For achieving the genetic progress, it is essential to know the genetic variability of crops, especially concerning yield and its attributes. Biofortification breeding focuses on the increased levels of iron and zinc in crops. The genetic variability in micronutrient levels varies substantially, impacted by soil nutrient levels, agronomic practices, environmental factors, and the hybrid or particular variety of crops.

The discovery of quantitative trait loci (QTLs) in a variety of crops has formed molecular marker assisted breeding easier (Norton et al., 2010). Grain Zn and Fe typically correlate, permitting for the contemporaneous improvement of both minerals by genetic enhancement. High genetic diversity in seed Zn and Fe contents exhibit by wild relatives of wheat, beside few emmer wheat accession containing too high Fe and Zn contents besides with a high protein concentration. The introversion of the elevated grain protein locus (Gpc-B1) from wild emmer wheat into cultivated durum wheat provide increased contents of Fe, Zn, protein, and Mn in the grain (Distelfeld et al., 2007). There is significant genetic variation in the Zn and Fe content of rice germplasm, that serves potential for breeding programs focused at increasing grain nutrient levels. Significant genetic variability of Fe and Zn among aromatic and indica rice types, besides among 46 analyzed rice genotypes. Pearl millet has a nutritional value of high level of metabolizing energy and protein and its more balance composition of amino acid. Advancement in processing technologies have led to the manufacture of health-oriented and alternative food items produced from pearl millet, providing a lower glycemic index as compared to similar wheat-origin items. Contrary to most vital cereals, pearl millet is free of gluten, allowing it a beneficial dietary choice for people with celiac disease or gluten intolerance. Moreover, it is less susceptible to the contamination of aflatoxin as compared to maize and sorghum. The eggs by chickens fed pearl millet-origin diet have less levels of low-density lipoprotein (LDL), allowing the generation of “designer eggs” best for people having increased cholesterol. These features emphasize the pearl millet’s potential to increase the nutritional security of deprived population in Sub-Saharan Africa and India, whereas also serving health benefits to wealthy circle finding healthier food choices. Though starchy endosperm exhibits a decreased contents of minerals such as zinc and iron due to the existence of anti-nutrient phytate, transgenic techniques allow a beneficial substitute. The synthesis of phytate can be reduced by mutagenesis, phytase-encoding genes can be represented by transgenesis, or genes that resulted to the iron formation in endosperm can be stated (Brinch-Pedersen et al., 2007). It is challenging to induce nutritional qualities in commodities such as cassava and bananas by conventional breeding, transgenesis is very significant.

Agronomic Biofortification through Fertilization and Crop Diversification

Since the presence of Se is low in the soils of Western Europe, areas of China, and Finland, New Zealand was first to introduce a national agronomic biofortification program in 1984 (Hartikainen, 2005). The Green Revolution has been questioned for promoting more immense cereal production at the charge of pulse crops and legumes (Welch & Graham, 2002). Extension of cropping system to involve further nutrient-rich crops would cause substantial advantages to people nutrition in regions with low incomes. The rice fish system is a great illustration of providing nutrition and economic values to agriculture, while there are limitations that should be tackle (Graham et al., 2007). Inter-cropping within graminaceous species and dicots can promote more effective utilization of nutrient resources and higher content of Zn and Fe in seeds (Zuo & Zhang, 2009). Four transgenic component biofortification initiatives are promoted by the Grand Challenges in Global Health Program. To increase the content of Fe in rice seeds, ferritin, a protein nanocage that can retain up to 4500 atoms of Fe3+, may be exaggerated in rice endosperm (Palmer & Guerinot, 2009). A metal chelator, Nicotianamine (NA), that is crucial for phloem transfer of iron to grain (Wirth et al., 2009).

Candidate Genes for Nutritional Enhancement

QTL analysis or marker assisted selection (MAS) are employed to recognize potential candidate genes for enhancing forage crops. In legume M. sativa, QTL has been utilized to study vigor and resistance (McCord et al., 2014), height of plant and candidate gene analysis for stem height and flowering by CONSTANS-LIKE (Herrmann et al., 2010). Markers are utilized to derive phenotypic traits and trace inheritance to help breeding. A complete re-iteration of the model forage M. truncatula genome has recognized hundreds of small, released peptides coded by both nodulation-responsive and macronutrient-responsive genes, which could help reverse genetics for enhancing many forage crops, specifically M. sativa (de Bang et al., 2017). Iterative mapping software like BioMercator (Sosnowski et al., 2012) has been employed in Lolium to show meta-QTL analysis applying easily accessible published data (Shinozuka et al., 2012), displaying new candidate genes from earlier work.

Protein and N-Budget

Forage nitrogen utilization (NUE) is a critical breeding aim especially as protein concentration of crop is highly significant. Forage crops need high nitrogen due to enhanced growth, higher fiber content, and storage capacity in contrast to grain crop which has been raised for increased seed starch (Parsons et al., 1991). The very essential nutrient for livestock are water-soluble carbohydrate (WSCs) and proteins, and preferably, the after harvesting attribute of these should be retained. Research has emphasized on establishing organ-specific proteome reference maps for leaves and stem, with photosynthetic enzymes like RuBiCO and RuBisCO small units (rbsS) contributing up 28.9% of leaf tissue. Transgenic approached have been employed to improve and boost amino acids and proteins, like by using soybeans and lupins as forage sources (Tabe et al., 2010).

Stresses can substantially transform nutritional content in forages, resulting to the recognition of 48 SRPs (stress-responsive proteins) for vegetative tissue (Chattopadhyay et al., 2011). Harvesting regimes can lead to the repositioning of VSPs (vegetative storage proteins) to increase new shoot regrowth and enhance cold tolerance in cultivars (Avice et al., 2003).

Rhizosphere Microbiome

Genomic research is expanding over crop plants to their ecosystem interface, with rhizosphere microbiota being a future aim for enhancing crop nutritional quality. Epiphytic bacteria living outside and inside plants might be crucial for nutrition and health of crop, and few microorganisms can take nitrogen inside the legume root system. Bacteria residing beside plants might help in absorption and digestion of forage taken by livestock, enhancing the intake of trace elements in the animal gut. The rhizosphere microbiome is necessary for uptake and cycling of nutrients, especially in less input systems such as those cultivated in the tropics. Induction of new forage crops with beneficent microorganisms is possibly to be an aim for future crops, combining with rhizosphere microbiota research of root exudate composition. Nitrification inhibitors have been recognized in root secretions from various grasses and legumes, involving rice and sorghum, however the largest action was observed in the Brachiaria humidicola (Teobaldi et al., 2017).

Digestibility

Protein uptake and digestion of livestock are straightly associated to energy availability (ME) (McCarthy et al., 1989), forming it necessary to enhance water storage capacity (WSC) in various forage crops, particularly grasses (Miller et al., 2001). In Lolium, WSCs involve fructans, that are the vital storage polysaccharide. Enhanced metabolism of fructan from sucrose might aid to boost the D-value (Chalmers et al., 2005), and employing unique Fructan:Fructan 6G- fructosyltransferase sequence variants has performed to enhance fructan contents at more warm temperatures in Lolium. The contents of WSCs are firmly linked with nitrogen availability to the root, emphasizing the significance of C: N balance in vegetative tissue (Louahlia et al., 2008). Modern advances in the recognition and manipulation of photosynthesis promotors for Chlorophyll a/b Binding (CAB) and Lolium perenne RBCS (Panter et al., 2017) have supplied transgenic lines for estimating boost in harvest, digestibility, and fiber, along with fructan contents in leaf blades and pseudostem in field trials.

CONCLUSION

Plant foods exhibit a critical role in individual health, supplying essential micronutrients and minerals. But over-utilization, especially of excessively-refined cereal-originated products, has caused an outbreak of problems like cardiovascular diseases, type 2 diabetes, and obesity. Crop biofortification can aid to tackle micronutrient malnutrition by enhancing other intervention techniques. The major benefit of biofortification involve more benefit/cost ratios and assessing the rural poor. But, the regulatory and development acceptance of transgenic crops might be 5-10 turns superior to traditional breeding, however yet little in contrast to classical public health interventions.

It is suggested that the nutritional content of crops can be significantly improved by targeted interventions. Genetically modified plants, new crop varieties, and farming systems contributing more diverse crop species can substantially enhance individual health and nutrition beyond the coming 20 years. Bioinformatics and Genomics have transformed biology, allowing forage breeders to enhance crop performance. By analyzing cultivar sequence information and employing GWAS for attributes like NUpE, excess protein, trace elements or nutritional content and yield can be enhanced. Gene editing technologies can aim SNPs in critical genes in model plants, and TILLING lines are utilized to study functions of genes in many forage crops. Sequence information can also be employed to establish PCR primers for identifying general health, tissue testing, and nutritional value of crops and particular pathogens. CRISPR/Cas9 techniques might supply a sustainable way for modifications, however bad genome editing efficiency is restricting advances. Future genome editing might come to be highly acceptable, especially to animal feedstock.