Swapan Kumar Datta

Alleviating micronutrients associated problems in children below five years and women of childbearing age, remains a significant challenge, especially in resource-poor nations. One of the most important staple food crops, wheat attracts the highest global research priority for micronutrient (Fe, Zn, Se, and Ca) biofortification. Wild relatives and cultivated species of wheat possess significant natural genetic variability for these micronutrients, which has successfully been utilized for breeding micronutrient dense wheat varieties. This has enabled the release of 40 biofortified wheat cultivars for commercial cultivation in different countries, including India, Bangladesh, Pakistan, Bolivia, Mexico and Nepal. In this review, we have systematically analyzed the current understanding of availability and utilization of natural genetic variations for grain micronutrients among cultivated and wild relatives, QTLs/genes and different genomic regions regulating the accumulation of micronutrients, and the status of micronutrient biofortified wheat varieties released for commercial cultivation across the globe. In addition, we have also discussed the potential implications of emerging technologies such as genome editing to improve the micronutrient content and their bioavailability in wheat.

Micronutrient deficiencies of iron, zinc, and vitamin-A are such serious global health issues, that it affects one out of every three people worldwide. The intensity of this “hidden hunger” compels us to acknowledge global nutritional security issues. Plant based food are the most popular and trending choices for people of all rungs of the social ladder. Biofortification is a sustainable and promising process of improving nutrition in plant based food through different agronomic approaches, conventional plant breeding and genetic engineering. Biofortified crops have been developed with high iron, high zinc, vitamin-A, with other nutritional quality enhancements and these crops have already proved to be a ‘boon for nutritional security’. This review highlights some selected Biofortified crops with special reference to rice (Oryza sativa), as 50% of the global population relies on it.

Phytic acid or Myo-inositol hexakisphosphate is an essential compound for the rice plants. It remains in the form of phytate, a mixed salt of different mineral cations, in the seeds. The phytate breaks down during germination and provides the inorganic phosphorus and mineral ions to the seedlings. However, humans do not get the benefit of those essential ions from rice consumption due to the absence of phytase in the gut. We envisaged down-regulating ITPK, the gene behind the phytic acid biosynthesis so that its low amount would facilitate a greater amount of free mineral ions in the endosperm. Since there are six homologues of rice ITPK, we studied their expression in seeds. Additionally, we undertook an in-silico analysis of the homologous proteins. Considering the results, we selected ITPK-2 for its RNAi-mediated embryo-specific down-regulation to obtain the low phytate rice. We obtained a 37% reduction of phytic acid content accompanied by a nearly three-fold enhancement of inorganic phosphorus in the transgenic seeds. Additionally, the iron and zinc content increased in polished rice grains compared to the wild type. The results also showed that reduced phytic acid content did not affect the germination potential and seedling growth of the transgenic rice.

The CRISPR/Cas9 technique for rice genome engineering is gaining momentum and requires a precise gene delivery system. For rice and other crop plants, Agrobacterium tumefaciens-mediated transformation (AMT) is considered a suitable gene transformation method. The AMT for indica-type rice is a challenge because it is less efficient in tissue culture response than japonica-type rice. Here is a protocol of the AMT method that we developed for IR64 variety which has been successfully tested in other popular indica-type rice varieties. We used embryogenic calli as explant and an empty gRNA-containing CRISPR/Cas9 vector with hptII (hygromycin phosphotransferase) gene for the transformation. This technique would speed up rice genome editing via CRISPR/Cas9 technology and facilitate to achieve varied application in the future.