Domestication quantitative trait loci inTriticum dicoccoides, the progenitor of wheat

Abstract

Wild emmer wheat, Triticum dicoccoides, is the progenitor of modern tetraploid and hexaploid cultivated wheats. Our objective was to map domestication-related quantitative trait loci (QTL) in T. dicoccoides. The studied traits include brittle rachis, heading date, plant height, grain size, yield, and yield components. Our mapping population was derived from a cross between T. dicoccoides and Triticum durum. Approximately 70 domestication QTL effects were detected, nonrandomly distributed among and along chromosomes. Seven domestication syndrome factors were proposed, each affecting 5-11 traits. We showed: (i) clustering and strong effects of some QTLs; (ii) remarkable genomic association of strong domestication-related QTLs with gene-rich regions; and (iii) unexpected predominance of QTL effects in the A genome. The A genome of wheat may have played a more important role than the B genome during domestication evolution. The cryptic beneficial alleles at specific QTLs derived from T. dicoccoides may contribute to wheat and cereal improvement. F rom agriculture origins in the Near East 10,000 years ago, emmer was the principal wheat of the newly established farming settlements, subsequently spreading 7,000 years ago to Egypt, India, and Europe (1). Wild emmer wheat, Triticum dicoccoides, genome AABB, is a tetraploid, a predominantly self-pollinating wild progenitor of modern tetraploid and hexaploid cultivated wheats (2, 3). T. dicoccoides proved important in wheat breeding in the past, and it deserves in-depth study as a potential genetic resource for cereal improvement (1).Analysis of quantitative trait (QT) loci (QTL) of domestication-related traits was studied in rice (4), maize (5), sorghum (6, 7), and millet (8). In recent years, QTLs were mapped in hexaploid wheat for agronomic traits (9, 10). To date, QTLs have been reported for tetraploid wheat mainly for quality traits (11, 12) but not for domestication traits. Grass domestication evolution is the key to exploiting genome diversity for future cereal improvement (13). Therefore, the objective of this study was to map genetic loci underlying domestication-related traits, including brittle rachis (Br), heading date (HD), plant height (HT), grain size, yield, yield components, and the genomic distribution pattern of domestication QTLs in T. dicoccoides. Materials and MethodsMapping Population. A cross was made between a highly striperust-resistant T. dicoccoides accession, Hermon H52 (H52) (1), with typical wild traits, from Mt. Hermon, Israel, and a Triticum durum cultivar, Langdon (Ldn). The F 2 mapping population consisted of 150 genotypes. Leaf samples were collected in the greenhouse at the elongation stage, frozen in liquid nitrogen, and stored at -80°C until DNA isolation (14). The F 2 individuals were bagged to ensure selfing for producing F 3 families.Phenotyping of Domestication-Related Traits. A randomized block design field experiment was conducted in Neve Yaar, Israel, from 1997 to 1998. The trial totaled 162 single-row plots, 150 for the F 3 fa...

Quantitative Trait Loci for Grain Yield and Adaptation of Durum Wheat (Triticum durum Desf.) Across a Wide Range of Water Availability

“…Comparative analysis with the known major QTL for yield in wheat: A survey of the literature reporting QTL for GY and related agronomic traits in both tetraploid and hexaploid wheat (Li et al 2002;Peng et al 2003;Elouafi and Nachit 2004;Huang et al 2004Huang et al , 2006McCartney et al 2005;Quarrie et al 2005Quarrie et al , 2007Marza et al 2006;Narasimhamoorthy et al 2006;Kuchel et al 2007;Kumar et al 2007;Ma et al 2007) revealed rather different scenarios for the two major GY QTL identified in our study. Our comparative analysis was carried out by relating the (LOD À 1) supporting interval of the QTL to the Ta-SSR-2004 consensus map (Somers et al 2004).…”

“…2BL (Bö rner et al 2002;Marza et al 2006), and QTL for GY, kernel weight, and number of kernels per spike have been reported on chr. 2AL (Bö rner et al 2002;Peng et al 2003;Huang et al 2004;McCartney et al 2005), but not in the distal region. Conversely, major QTL for GY have been identified in two different genetic backgrounds (Bö rner et al 2002;Campbell et al 2003) on the short distal regions of chr.…”

Association Mapping of Kernel Size and Milling Quality in Wheat (Triticum aestivum L.) Cultivars

“…Yet another possible explanation for the LD block on 5A would be the loss of variability during domestication, in which case the LD block should exist in other wheat classes as well. An important domestication-related QTL that affected grain weight, grain number per spike, plant height, heading date, and yield per plant has been detected in this region (Peng et al 2003).…”

AB-QTL analysis in winter wheat: I. Synthetic hexaploid wheat (T. turgidum ssp. dicoccoides × T. tauschii) as a source of favourable alleles for milling and baking quality traits

“…dicoccoides) should also be useful, allowing detection of favourable alleles from both the tetraploid and diploid exotic parents. Wild emmer proved already as a donor of useful genetic variation for important agronomic traits in tetra-and hexaploid wheat, contributing to powdery mildew resistance, rust resistance, reduced plant height, early heading, increased number of spikes per plant, higher spike weight per plant, increased kernels per spikelet and higher yield (Peng et al 1999(Peng et al , 2003Rong et al 2000). Wild emmer also proved to possess genes improving grain quality in wheat.…”