Characterization of 14 Triticum species for the NAM-B1 gene and its associated traits.

BACKGROUND: Wheat grain protein, zinc (Zn), and iron (Fe) content are important wheat qualities crucial for human nutrition and health worldwide. Increasing these three components simultaneously in wheat grains by a single gene came into the picture through NAM-B1 cloning. NAM-B1 gene and its association with the mentioned grain quality traits have been primarily studied in common and durum wheat and their progenitors T. dicoccum and T. dicoccoides. METHOD: In the present study, for the first time, 38 wheat accessions comprising ten hexaploids from five species and 28 tetraploids from nine species were evaluated in the field for two consecutive years. Additionally, the 582 first nucleotides of the NAM-B1 gene were examined. RESULT: The NAM-B1 gene was present in 21 tetraploids and five hexaploid accessions. Seven tetraploid accessions contained the wild-type allele (five T. dicoccum, one T. dicoccoides, and one T. ispahanicum) and fourteen the mutated allele with a 'T' insertion at position 11 in the open reading frame, causing a frameshift. In hexaploid wheat comprising the gene, only one accession of T. spelta contained the wild-type allele, and the rest resembled the insertion mutated type. In the two-year field experiment, eight accessions with the wild-type NAM-B1 allele had significantly higher protein, Zn and Fe grain content when compared to indel-type accessions. Additionally, these accessions exhibited a lower mean for seed-filling duration than all other accessions containing indel-type alleles. In terms of grain yield, 1,000-kernel weight, kernel diameter, and kernel length, T. dicoccum accessions having wild-type alleles were similar to the indel-type accessions over two years of evaluation. CONCLUSION: These findings further support the possibility of simultaneous improvement of wheat grain protein, Zn, and Fe content by a single gene crucial for human nutrition and health worldwide.

Analysis of Yellow Striped Mutants of Zea mays Reveals Novel Loci Contributing to Iron Deficiency Chlorosis.

The micronutrient iron (Fe) is essential for photosynthesis, respiration, and many other processes, but it is only sparingly soluble in aqueous solution, making adequate acquisition by plants a serious challenge. Fe is a limiting factor for plant growth on approximately 30% of the world's arable lands. Moreover, Fe deficiency in humans is a global health issue, affecting 1.62 billion people, or about 25% of the world's population. It is imperative that we gain a better understanding of the mechanisms that plants use to regulate iron homeostasis, since these will be important targets for future biofortification and crop improvement strategies. Grasses and non-grasses have evolved independent mechanisms for primary iron uptake from the soil. The grasses, which include most of the world's staple grains, have evolved a distinct 'chelation' mechanism to acquire iron from the soil. Strong iron chelators called phytosiderophores (PSs) are synthesized by grasses and secreted into the rhizosphere where they bind and solubilize Fe(III). The Fe(III)-PS complex is then taken up into root cells via transporters specific for the Fe(III)-PS complex. In this study, 31 novel, uncharacterized striped maize mutants available through the Maize Genetics Cooperation Stock Center (MGCSC) were analyzed to determine whether their mutant phenotypes are caused by decreased iron. Many of these proved to be either pale yellow or white striped mutants. Complementation tests were performed by crossing the MGCSC mutants to ys1 and ys3 reference mutants. This allowed assignment of 10 ys1 alleles and 4 ys3 alleles among the novel mutants. In addition, four ys∗ mutant lines were identified that are not allelic to either ys1 or ys3. Three of these were characterized as being non-allelic to each other and as having low iron in leaves. These represent new genes involved in iron acquisition by maize, and future cloning of these genes may reveal novel aspects of the grass iron acquisition mechanism.