Genetic diversity in the U.S. hard red winter wheat cultivars as revealed by microsatellite markers

Abstract

Abstract. Knowledge of the genetic diversity existing in previously released hard red winter wheat (HRWW, Triticum aestivum L.) cultivars in the Great Plains region, United States, is essential for effective utilisation of these genetic resources in the various HRWW breeding programs. To ascertain a measure of the genetic diversity of the existing US HRWW, 60 cultivars were analysed with 62 microsatellite markers distributed throughout the wheat genome. Marker data were subjected to distance-based analysis and analysis of molecular variances. In total, 341 polymorphic alleles were scored with a range of 2-12 alleles per locus. Genetic diversity gradually increased in cultivars released after the 1970s. Cultivars released in the 1990s had the highest allelic richness (4.79), gene diversity (0.60), and polymorphic information content (0.56). Levels of genetic diversity were similar between the major HRWW breeding programs. Cluster analysis resulted in eight clusters. Cluster grouping gave close matches with pedigrees and with regional distribution of the cultivars. Using decadal information, cultivars released from 1900-1969 were grouped into one cluster, cultivars from 1990-2005 were grouped into a separate cluster, whereas cultivars from the 1980s did not group with any other decades. Analysis of molecular variance revealed a significant variation among the clusters, signifying that a true genetic variation existed among the clusters. The higher proportion of genetic variation explained by cultivars within clusters compared with among clusters indicates greater genetic diversity among cultivars within clusters. Our results indicate that genetic diversity of Great Plains HRWW cultivars has increased in the past century, and the trend is continuing.

Analysis of Genetic Diversity in Synthetic Wheat Assemblage (T. turgidum^|^times;Aegilops tauschii; 2n=6x=42; AABBDD) for Winter Wheat Breeding

“…These higher allelic numbers and gene diversity information may be attributed to the use of a high number of germplasm lines, use of landraces and diverse germplasm maintained at gene bank. The PIC values revealed significant variability among different SSRs in terms of molecular polymorphism, which is in agreement to the report of Prasad et al (2009). Further computing the MI facilitated unrevealing the allelic richness of SSRs within these WSHs where chromosomes 1D, 3D and 6D possessed greater allelic richness and had slightly different (non-significant) values for MI as compared to other four D-genome chromosomes.…”

“…Genetic diversity present within winter synthetic hexaploids (WSHs) can add value by introducing new allelic variation into products where breeding and intensive selection pressure have reduced allelic diversity, causing major constraints for winter wheat improvement emerged within the modern agriculture system (Prasad et al 2009, Karsai et al 2012. The challenges faced by winter wheat breeders in the Great Plains (the largest winter wheat producing area in the USA) include moderate to high incidence of aphids, green bugs and Russian wheat aphids.…”

“…Winter wheat in Western Europe and NW USA contributes to global food security (Prasad et al 2009). The high production of winter wheat grain in USA provides export grains for regions of the world which are not self sufficient in wheat grain like Africa and the Middle East.…”

Assessing genetic diversity of wheat genotypes from different origins by SNP markers

“…But anyway cluster grouping gave close matches with some pedigrees and distribution of the genotypes based on the origin. Some authors such as Prasad et al (2009) had also the similar conclusions. This paper confirmed the hypothesis that the relationship of parents placed genotypes into the same groups on the basis of common alleles.…”

Investigation of Genetic Diversity among Bread Wheat Cultivars (Triticum aestivum L.) Using SSR Markers

“…In that study, they found that genetic diversity gradually increased in cultivars released after the 1970s and cultivars released in the 1990s had the highest allelic richness. Cluster grouping gave close matches with pedigrees and with regional distribution of the cultivars (Prasad et al, 2009). Hai et al (2007) using 52 SSR markers studied genetic diversity of 69 accessions of spring bread wheat and showed that the polymorphism index content value varied from 0.24 to 0.89 with an average of 0.68.…”