Authors: Ruchi V. Trivedi, Bhupendra singh Punwar, Tejas Gohil and Jignash Patel
Introduction
Access to healthy diet is a fundamental right of every human being on this planet. Nearly 870 million people, or one in eight, suffered from chronic undernourishment in 2010- 2012, according to the new United Nation hunger report. The nutritional considerations in food crops comprise amino acids especially the essential amino acids, carbohydrates, essential oils, minerals (mainly, iron (Fe), zinc (Zn)), vitamins (mainly vitamin A) and secondary metabolites. The proper intake of these nutrients is extremely vital for growth and development in human beings. Thus, a proper balance in diet helps keeping in bay with the deficiencies and diseases. The main source of protein, vitamins and minerals especially, for low income rural and urban populations are staple foods of plant origin. These foods often contain low bioavailability of the micronutrients (Monasterio et al., 2007). In addition, the anti-nutritional compounds primarily phytic acid present in the food grain reduce the bioavailability of the minerals hampering its nutritive values. Development of food crops with enhanced nutritional traits is a prime requirement which can be catered and achieved through combination of conventional and molecular breeding. Employment of molecular markers for tracking a particular trait of quality parameters through marker-assisted selection proves to be an efficient way for developing new nutritionally enriched varieties.
Methods to improve quality in crops
- Breeding methods
- Conventional breeding
- Bi-parental mating
- Marker-assisted selection
- Back-cross breeding
- Mutation breeding
- Association mapping
- Transgenic techniques
- Recombinant DNA technique
Case studies
Ellis and Pantalone (2009) developed a commercially acceptable, superior quality, high yielding soybean cultivar with low seed phytate. In order to incorporate the low phytate trait into regionally adapted soybean cultivar ‘5601 T’ was used for series of backcrosses and marker assisted selection (MAS).
Tiwari et al., (2009) crossed Triticum monococcum and Triticum boeoticum for generation of a recombinant inbred line (RIL) population. The grains for these RILs were evaluated for Fe and Zn concentration and used for QTL mapping which identification of two QTLs for Fe on chromosome 2A and 7A and one QTL for grain Zn on chromosome 7A.
Babu et al., (2011) crossed a high Zn content line, Chittimutuyalu with BPT 5204 and developed a variety possessing a high Fe and Zn content.
Ming et al., (2011) studied 48 and 64 QTLs respectively for 2 yrs, obtained from F9 recombinant inbred line population derived from a cross between Zhenshan 97B and Delong 208. Out of these, three QTLs for amino acids qAa1, qAa7 and qAa9 were identified.
Blair and Izquierdo (2012) developed an approach for transfer of the seed mineral trait from wild beans to cultivated beans through the advanced backcross. They reported that that the cross had high polymorphism and constructed an anchored microsatellite map for the population that was 1,554 cM long and covered all 11 linkage groups of the common bean genome.
Ashok Kumar et al., (2012) assessed core germplasm collections (>2200) for enhancing Fe and Zn contents of the sorghum grain and identified promising donors. Significant positive association was observed between grain Fe and Zn contents which indicated the feasibility to develop high Fe and Zn containing cultivars with high yielding and different maturity backgrounds.
Lachman et al., (2012) evaluated wild varieties of wheat viz., einkorn wheat, emmer wheat and spring wheat for antioxidant activity (AOA) using 2, 2- diphenyl-1-picrylhydrazyl assay (DPPH). The higher grain AOA was observed in emmer and einkorn varieties than the cultivated spring wheat varieties. Thus, wild relatives proved to be promising sources for improving AOA in cultivated wheat through breeding approaches.
Ahmad et al., (2013) screened 10 wheat genotypes for phytic acid content and selected five genotypes for generating 5 x 5 full diallel set for studying the inheritance of phytic acid. It was confirmed that F1 hybrid with low phytic acid concentration could yield desirable segregant population.
Gupta et al., (2013) improved hybrid Vivek by backcrossing and converted it to Quality Protein Maize (QPM) with an improved amino acid content with 41% increase in tryptophan and 30% increase lysine over the original hybrid .
Pillay et al., (2013) analyzed 32 pro-vitamin varieties for protein and mineral content. The results indicated that biofortified maize sources of essential amino acids compared to the white variety, but similar to white maize they were deficient in histidine and lysine.
Tako et al., (2013) compared Fe-bioavailability between recombinant inbred lines developed from two maize varieties i.e., B37 and M017 (Intermated B37xMO17) and selected lines with high and low Fe content. These lines were further backcrosses with the original parents and evaluated in human cell culture and chicken feed for bioavailability.
Success Stories
An open pollinated variety of pearl millet, ICPT 8203 was developed at ICRISAT in 1982 from selection within Iniadi landrace from northern Togo. ICPT8203 was found to have the highest level of iron density among a diverse range of populations OPV and hybrids in trials conducted during 2004-2008. By exploiting intra-population variability for iron density within it, one of its improved versions, ICTP 8203 Fe-10-2 (ICTP 8203 Fe for short), was developed and released as ‘Dhan Shakti’ in Maharashtra in August 2013 (HarvestPlus and ICRISAT, India).
Three accessions were selected for high Fe and Zn content in Bangladesh and evaluated at multilocations. High Fe rich variety, Dhan 62 was released by Bangladesh Rice Research Institute in 2013 through selection (HarvestPlus and Bangladesh Rice Research Institute, Bangladesh).
Conclusion
⥤ Exploitation of wild relatives serves as a source of novel alleles and broadens the genetic base by the quality consideration like proteins, minerals vitamins enhanced through conventional and molecular breeding.
⥤ Marker-assisted selection was effectively utilized for co-operating economic traits into popular varieties and reducing anti-nutritional factors.
⥤ Quantitative trait loci for various traits like grain iron, zinc, protein, amino acids were identified.
⥤ Advanced back cross QTL method was used to transfer nutrient traits from wild to cultivated crop.
Future thrust
⥤ AB-QTL should be highly employed for transferring alleles economic into cultivated crop varieties from wild germplasm.
⥤ More number of yield trials for biofortified crops varieties should be carried out at different agro climatic zones for suitability in the regions.
⥤ Molecular breeding should be carried out keeping pace simultaneously with enhance nutritional content for bioavailability.
Germplasm mini core / core collection should be exploited for superior elite alleles.
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About Author / Additional Info:
I did Ph. D in plant molecular biology and biotechnology and 3 years of research experience in the same.