Imran Sheikh

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.

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.

Uptake, distribution, and remobilization of iron and zinc among various tissues of wheat–Aegilops substitution lines at different growth stages

Biofortification of wheat for higher grain iron and zinc is the most feasible and cost-effective approach for alleviating micronutrient deficiency. The non-progenitor donor Aegilops species had 2–3 times higher grain iron and zinc content than the wheat cultivars, whereas the wheat–Aegilops substitution lines mostly of group 2 and 7 chromosomes had intermediate levels of grain micronutrients. The non-progenitor Aegilops species also had the highest iron content and intermediate-to-highest zinc content in straw, lower leaves, and flag leaves at the pre-anthesis, grain-filling, and maturity growth stages. The micronutrients accumulation status is followed by wheat–Aegilops substitution lines and is the least in wheat cultivars indicating that the donor Aegilops species and their substituted chromosomes possess genes for higher iron and zinc uptake and mobilization. The grain iron content was highly positively correlated with iron content in the plant tissues. Most of the lines had much higher iron and zinc content in all tissues during grain-filling period indicating higher iron and zinc uptake from soil during this stage. Although iron and zinc contents are nearly similar in grains, there was much less zinc content in the plant tissues of all the lines suggesting that the Triticeae species take up less zinc which is mobilized to grains more effectively than iron.

Marker-Assisted Breeding of Recombinant 1RS.1BL Chromosome for Improvement of Bread Making Quality and Yield of Wheat ( Triticum aestivum L.)

The 1RS.1BL translocation has been extensively used as a source of genes on 1RS for multiple disease resistance (Lr26, Yr9, Sr31 and Pm8) and enhanced yield of wheat cultivars. However, cultivars with the 1RS.1BL translocation have sticky dough due to the presence of Sec-1 on 1RS and absence of Glu-B3/Gli-B1 on 1BS. Many QTL useful for root traits have also been mapped on 1RS. A tertiary recombinant 1RS line lacking Sec-1 but with useful root QTL and Glu-B3/Gli-B1 of 1BS has been developed at the University of California, Riverside USA which is being used for marker-assisted breeding of wheat cultivars for higher yield and improved bread making quality. PCR-based SSR markers (ω-sec-P3/P4, Rye R3/F3, Psp3000, Sfr 43) were used to check the presence of Sec-1, rye translocation, Glu-B3/Gli-B1 and Pm8 for characterization of wheat cultivars and 1RS recombinants, respectively. The markers amplified the desired amplicons and were well synchronized to each other about the presence and absence of various genes in each cultivar and recombinants. The absence of Pm8 and poor root traits in MA1Pavon confirmed the close association between Pm8 and useful root QTL. Two of the recombinants, i.e., 1B+38 and 1RS44:38 were found to have Pm8 gene as well as better root traits than in MA1Pavon. The SDS micro-sedimentation test of various 1RS recombinants and parental lines showed that 1RS–1BL with Sec-1 had lowest micro-sedimentation test (MST) value while addition of Glu-B3/Gli-B1 had negligible improvement. These findings suggest that the MST values are not much affected by the absence of Glu-B3/Gli-B1 and hence the lines having better root traits with no Glu-B3/Gli-B1 and secalin could be used for improvement of bread making quality and yield in wheat.

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.

Transferability and Polymorphism Between Group 7 Chromosome Specific Simple Sequence Repeat (SSR) Markers of Bread Wheat and Its Related Non-Progenitor Aegilops Species

ABSTRACT Simple sequence repeat (SSR) markers are highly efficient for genetic mapping and molecular breeding in crop plants. Chromosomes 7S and 7U of related non-progenitor Aegilops species possess superior genetic systems for high grain iron and zinc content. This study was undertaken to conduct a comprehensive analysis of transferability and polymorphism among group-7 anchored SSR markers of bread wheat (Triticum aestivum L.) to Aegilops species for wheat improvement. The study revealed 77% transferability of group 7-specific SSR markers of bread wheat to 7U/7S chromosomes of Aegilops species. More than 80% of the 7D specific markers were found to be transferable with a high level of polymorphism. The transferability to 7S and 7U genome suggested higher similarity between bread wheat genome(s) and S genome as compared with U genome of Aegilops species. These polymorphic markers are highly informative, robust and cost-effective for molecular breeding and could be further utilized for identification of introgression/transfer(s) of 7S/7U chromosomal fragments in bread wheat genome through wide hybridization.