Vishal Chugh

Transfer of useful variability of high grain iron and zinc from Aegilops kotschyi into wheat through seed irradiation approach

Abstract Purpose To transfer the 2S chromosomal fragment(s) of Aegilops kotschyi (2Sk) into the bread wheat genome which could lead to the biofortification of wheat with high grain iron and zinc content. Materials and methods Wheat-Ae. kotschyi 2A/2Sk substitution lines with high grain iron and zinc content were used to transfer the gene/loci for high grain Fe and Zn content into wheat using seed irradiation approach. Results Bread wheat plants derived from 40 krad-irradiated seeds showed the presence of univalents and multivalents during meiotic metaphase-I. Genomic in situ hybridization analysis of seed irradiation hybrid F2 seedlings showed several terminal and interstitial signals indicated the introgression of Ae. kotschyi chromosome segments. This proves the efficacy of seed radiation hybrid approach in gene transfer experiments. All the radiation-treated hybrid plants with high grain Fe and Zn content were analyzed with wheat group 2 chromosome-specific polymorphic simple sequence repeat markers to identify the introgression of small alien chromosome fragment(s). Conclusion Radiation-induced hybrids showed more than 65% increase in grain iron and 54% increase in Zn contents with better harvest index than the elite wheat cultivar WL711 indicating effective and compensating translocations of 2Sk fragments into wheat genome.

Chapter 9 – Biofortification of Staple Crops

Half of the world population suffers from deficiencies in micronutrients—iron, zinc, vitamin A—largely among the people of developing countries depending on staple cereals, and these deficiencies may lead to health risks and even death in acute cases. The staple food crops are inherently low in micronutrients, and these are further reduced during grain and food processing. Among the various strategies to combat micronutrient malnutrition, biofortification may prove to be the most economical, feasible, and sustainable approach to increase the mineral content of staple food crops. Biofortified crops also bear the potential to enhance the agronomic efficiency of plants on mineral-poor soils. Biofortification involving enhanced uptake of minerals from soil, their transport to the leaves, and improved sequestration in the edible tissues of grains, is being done through combination of conventional and molecular breeding and genetic engineering. Bioavailability of micronutrients from cereal-based diets is also crucial and can be enhanced by lowering the anti-nutritional compounds like phytic acid and simultaneously increasing promoters of mineral absorption, such as ascorbic acid, inulin, and β-carotene. Thorough understanding of the molecular basis of micronutrient uptake, transport, and deposition in various grain tissues will further strengthen the biofortification program to enhance the micronutrients and minimize their losses during processing.

Characterization of interspecific hybrids of Triticum aestivum x Aegilops sp. without 5B chromosome for induced homoeologous pairing

In the present study we aimed to characterize the interspecific hybrids made between Triticum aestivum cv. Pavon monosomic for chromosome 5B with different accessions of Aegilops kotschyi (UUSS) and Aegilops peregrina (UUSS) at cytological, molecular and morphological basis. Molecular analysis using Ph1 locus specific dominant marker and cytological analysis clearly differentiated between F1 hybrids (ABDUS) with and without 5B chromosome. Plants without chromosome 5B showed stunted and bushy growth habit with reduced height and more number of tillers per plant while those with 5B plants showed normal growth. Agreement of morphological observations with the cytological and molecular results indicates that the morphological characteristics could also be used to screen plants without 5B chromosome. The results clearly demonstrated that the absence of chromosome 5B through the use of Pavon monosomic for chromosome 5B can be an efficient way to induce homoeologous pairing between chromosomes of wheat and Aegilops species for precise introgression of useful variability.

Evaluation of iron and zinc in grain and grain fractions of hexaploid wheat and its related species for possible utilization in wheat biofortification

Iron (Fe) and zinc (Zn) contents in hexaploid wheat are very low and are further reduced because of the removal of micronutrient-rich bran of wheat grains during milling and processing. Therefore, hexaploid wheat, its wild species and wheat– Aegilops kotschyi substitution lines were evaluated to identify the genome(s) carrying gene(s) for high Fe and Zn concentrations in bran and endosperm fractions of grains. It is reflected from the results that Triticum monococcum (acc. W463) may serve as a promising donor for biofortification of Fe, and Aegilops speltoides (acc. 3804) may serve as a promising donor for biofortification of Zn in the endosperm of cultivated wheat. Further, among the three wheat– Ae. kotschyi substitution lines, the higher concentration of Fe and Zn in endosperm fraction was observed in BC 2 F 4 63-2-13-1. The work on precise transfer of useful gene(s) from 7U k chromosome of this line is in progress to reduce linkage drag.