Variability in seed mineral composition of foxtail millet (Setaria italica L.) landraces and released cultivars

Abstract

Foxtail millet (Setaria italica L.) belongs to poaceae and an important research model plant to explore nutritional pathways. The present study represents a comprehensive micronutrient report of twenty landraces, four released cultivars, and their genetic variability in micronutrient content. FT-IR analysis recorded various absorption peaks at different wavelenths coressponding to certain chemical compounds and functional groups such as carbohydrates, alkenes, proteins, sulfur compounds, amines and lipids, etc, indicate that all the studied genotypes endowed with carbohydrates, proteins and lipids. The ICP-OES analysis revealed a wide range of variation in micronutrient concentrations across the studied genotypes i.e Iron (3.69 to 7.51mg/100g), Zinc (4.54 to 5.71 mg/100g), Calcium (13.13 to 39.58 mg/100g), Potassium (219.43 to 349.47 mg/ 100g), Copper (0.60 to1.09 mg/100g), Manganese (1.05 to 1.64 mg/100g). The PCA and cluster analaysis highlight a wide range of genetic variability among the genotypes. Further, these genotypes were clustered into six variables based on the micronutrient content. In overall performance of landraces better than released cultivars in terms of micronutrient content. Landraces like S1G4, S1G2; and relesed varity Narasimharaya recorded higher quatities of micronutrient compared to other genotypes studied. These genotypes would be useful to fish out the genes responsible for higher micronutrient occumulation and also as parental lines in breeding progrmmes to develop enhanced micronutrient genotypes. Introduction Plant-based foods contribute an array of nutrients that are essential for the day-to-day needs of human beings and they endorse good health. Humans require at least twenty-two micro and macro elements for their proper health, growth, and development (50). However, global estimates suggest that, over 60% of the people suffering from iron (Fe), 30% zinc (Zn), 30% iodine (I) and 15% selenium (Se) deficiencies. In addition to them, calcium (Ca), manganese (Mn), and copper (Cu) deficiencies are common in many of the developed and developing countries (40). Malnourishment is a global issue; especially developing countries from Asia and Africa facing severe micronutrient deficiencies in their dietary food (19, 42). The health and diet are codependent; the physiological functions of the human body are influenced by food components (29). Even though the requirements of micronutrients are minimal, they play a crucial role in proper growth and development. The deficiencies of micronutrients cause severe health complications such as physical and mental Variability in seed mineral composition of foxtail millet Current Trends in Biotechnology and Pharmacy Vol. 14 (3) 239-255, July 2020, ISSN 0973-8916 (Print), 2230-7303 (Online) DOI: 10.5530/ctbp.2020.3.25 240 Gurulakshmi et al retardation, blindness, gastrointestinal health complications, reduced immunity, etc. (9). Newborn babies and pregnant women of India severely affected by micronutrient deficiency and most of the infants are born underweight. It is estimated that nearly 7.4 million children remain undernourished (19). Thus, functional foods are gaining importance in the prevention and/or treatment of diseases. Among the plant-based foods, cereals alone play a key role as a staple food and provide ~50% of the dietary requirements of humans. Globally, among the cereals rice alone provides 50-60% of required calories to 2.7 billion people. However, the principle drawback of rice-based food products are being low in iron, zinc, proteins, vitamins, and other essential nutrients along with high water requirements for its cultivation (18, 50). On contrary small millets consists of diverse micronutrients, rich in essential amino acids and high water use efficient, grow in harsh environmental conditions, resistant to abiotic and biotic stress conditions. Hence, recently small millets gaining more importance and they might play a crucial role as functional foods. The small millet, foxtail millet (Setaria italica L.) is an important nutritious crop belongs to the family Poaceae, known for its origin from China. Due to its drought tolerance capacity, it is very well grown in semi-arid regions such as South Asia and Sub-Saharan Africa as nutritional food. It is also cultivated in South Korea, North Korea, Japan, Russia, Australia, France and the United States as a forage crops, feed for birds and cattle (12). Foxtail millet endowed with high amounts of protein, vitamins, minerals, starch, and fat content (39). It has twice the content of protein and fat as compared to rice (35). Nutrient analysis of core collection of foxtail millet seeds revealed that it had a wide range of nutrients such as calcium (171.2–288.7 mg/kg), iron (58.2–68.0 mg/kg), zinc (54.5–74.2 mg/kg) and protein (15.6–18.5%) (43). However, due to the presence of anti-nutrients made them less bioavailable (1, 2, 15, 23, 30). Bio-fortification of millets is an emerging approach to overcome the problem of anti-nutrients and to add more nutritional content to the crop plants. Conventional breeding, agronomical practices, and biotechnological strategies are the key approaches to improve the bio-fortification of crop plants. Agronomical practices such as supplementing the deficit soil with inorganic fertilizers were successfully practiced in Finland and Turkey for the high accumulation of Se and Zn in the seeds (50). Genetic variation for the trait of interest is a prerequisite for plant breeding (13). Foxtail millet genotypes exhibited variation in seed protein, fat, starch, and amino acids (51); Fe content (31); vitamin E (25); cooking quality traits (38). Thippeswamy et al (2017) screened 25 genotypes and identified two genotypes namely GS78 and GS71 as superior for grain micronutrients (Zn, Fe, and Ca) and protein content (41). Four genotypes of foxtail millet genotype 00002, 0011 (red colour bran) and Slovenský, Friderica (yellow colour bran) displayed varied amounts of nutritive components, fatty acids, phenolic compounds and antioxidants (28). A greater amount of variability was observed in 78 elite genotypes for nutritional parameters such as moisture, protein, fat, crude fibre, carbohydrate, total minerals, total energy, and micronutrients (Cu, Mn, Zn, and Fe) (7, 21). Landraces are a heterogeneous population, well adapted to local climatic conditions, and are extremely nutritious. They also serve as genetic material to breed high nutritional and stress adapted genotypes (11). Maxican maize landraces were successfully used to breed highquality protein maize lines and cultivars (32). Similarly, Sorghum popular Indian landrace Maldandi (M35-1) was used in the breeding programme to develop several restorer lines (ICSR#) and cultivars (ICSV#) (34). In pearl millets West African drought tolerant landrace “Iniadi” was used to develop several cultivars e.g.: ICTP 8203 (33). As many as 245 foxtail millet traditional varieties from different regions of Shanxi, China was evaluated for seed folic acid variability and Current Trends in Biotechnology and Pharmacy Vol. 14 (3) 239-255, July 2020, ISSN 0973-8916 (Print), 2230-7303 (Online) DOI: 10.5530/ctbp.2020.3.25 241 found a wide variability ranging (0.37–2.37 mg/g) of which 24 varieties with higher folic acid content were identified, among them, Jingu 21, a major leading cultivar, recorded folic acid content of 2 mg/g (36). Similarly, a panel of 92 foxtail millet landraces preserved by Taiwan indigenous peoples were assessed for seed amylase content (AC) using a rapid viscosity analyzer (RVA). A huge range of diversity (0.7% to 16.9%) in physiochemical properties was observed among the studied genotypes (52). Thus, identification of elite genotypes for micronutrient content is very important towards the development of improved varieties through classical as well as modern tools. To identify the elite nutritious genotypes in the present study, twenty local landraces collected from various locations of Andhra Pradesh and four released cultivars were selected, nutrient content was analysed using modern analytical tools such as ICP-OES (Inductively coupled plasma atomic emission spectroscopy) and FT-IR (Fourier Transform Infrared Spectrophotometer) and data were subjected to multivariate statistical analysis. Materials and Methods Plant material : The seeds of foxtail millet landraces collected from the farmer fields of Rayalaseema region, Andhra Pradesh, and twenty pure lines were developed by single seed descent method (SSD). The details of their development and molecular characterization were described elsewhere (Ramesh et al., manuscript Unpublished). Twenty pure landraces along with four released cultivars (Table.1) were surfaced sterilized with 0.01% HgCl2 followed by rinsing with distilled water. Seeds were sowed in the well-prepared seedbeds of natural field soil in a completely random blocked design with three replicates per sample. Each genotype was grown in three rows in net house at Yogi Vemana University, Kadapa, Andhra Pradesh under natural environmental conditions (30±1oC/37±1oC and relative humidity varied from 50-80%), by following standard agriculture practices. Seeds were harvested from panicles after maturation and stored in a cool dry place until further use. The seeds were de-husked and milled into flours by using a clean and sterilized mortar and pestle. The flours were kept at 55° C for 4-5 hours in a hot-air-oven to remove the moisture content if any. Dehydrated flours were subjected to nutrient analysis for macro, micronutrients, and essential biochemical groups. Sample preparation and FTIR Analysis : Dehydrated flour of all twenty-four genotypes was used for the preparation of KBr (potassium bromide) pellets to analyze functional groups of flour. Ten mg of dehydrated seed flour was mixed with 100mg of KBr and vigorously ground into a fine powder with mortar and pestle. This mixture was compressed into diaphanous