Functionality of chemically modified wild-type, partial waxy and waxy starches from tetraploid wheats
Partial waxy (reduced-amylose) and fully waxy (amylose-free) tetraploid durum wheats (Triticum turgidum L. var durum) were developed by introgression of null alleles at the Wx-A1 and Wx-B1 loci from common hexaploid wheat (Triticum aestivum L.). Purified starches were obtained from each genotype, and chemically modified by: 1) cross-linking with phosphorus oxychloride, 2) substitution with propylene oxide, and 3) sequential cross-linking with phosphorus oxychloride followed by substitution with propylene oxide. Functional properties were compared to blends of waxy and wild-type durum starches of known amylose contents. Significant differences in functionality were observed amongst the genotypes and blends after each modification. Waxy (0% amylose) and wild-type (30% amylose) typically were at the extremes of the observed ranges of functional properties. In general, the functional properties of the chemically modified starches were dependent upon amylose content. Starches from Wx-B1 null lines (24% amylose), were an exception. After substitution, such starches had the significantly highest value for RVA final viscosity, and generally performed in a manner similar to starch blends of 12–18% amylose.
Functionality of native tetraploid wheat starches: Effects of waxy loci alleles and amylose concentration in blends
Partial waxy (reduced amylose) and fully waxy (amylose-free) tetraploid durum wheats (Triticum turgidum L. var. durum) were used to investigate the relationships between both intra- and inter-granular variation in amylose concentration and starch functionality. Starches isolated from each genotype (intra-granular amylose variants) were compared to those of commercially available hexaploid wild-type and waxy starches, and functionalities compared to blends (inter-granular variants) of durum waxy and wild-type starches of 0, 6, 12, 18, 24, & 30% amylose content. Starch particle size distributions were not significantly different amongst partial waxy and wild-type genotypes; waxy samples had significantly smaller mean starch granule size. Few significant differences for crystallite melting and related intrinsic heat as determined by differential scanning calorimetry (DSC) were observed. The detected differences in starch gel color or gel strength generally were observed for the waxy samples relative to wild-type. Numerous significant differences were observed via Rapid-Visco Analysis (RVA). Pasting peak viscosity and breakdown were inversely proportional to % amylose. Wx-B1 null final viscosity differed significantly from that of all other blends and genotypes, demonstrating that genotypic differences exist amongst the partial waxy types, independent of amylose concentration per se.
Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes
Background After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. Review Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. Conclusions Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.