A molecular-marker map of bread wheat having many markers in common with other grasses in the Gramineae family is a prerequisite for molecular level genetic studies and breeding in this crop species. We have constructed restriction fragment length polymorphism maps of the A-, B-, and D-genome chromosomes of homoeologous group 2 of hexaploid wheat (Triticum aestivum L. em. Thell) using 114 F7 lines from a synthetic x bread wheat cross and clones from 11 libraries. Chromosomes 2A, 2B, and 2D comprise 57, 60, and 56 markers and each spans about 200 cM. Comparisons between chromosomes are facilitated by 26 sets of homoeoloci. Genes mapped include a heterologous abscisic acid responsive locus cloned as pBS128, the epidermal waxiness inhibitor W21, and two presumed leaf rust and stem rust resistance genes. Anomalies suggesting ancestral rearrangements in chromosome 2B are pointed out and features of wheat group 2 chromosomes that are common to barley (Hordeum vulgare L.), rice (Oryza spp.), and T. tauschii are discussed.

Conventionally, the genetics of species of the family Gramineae have been studied separately. Comparative mapping using DNA markers offers a method of combining the research efforts in each species. In this study, we developed consensus maps for members of the Triticeae tribe (Triticum aestivum, T. tauschii, and Hordeum spp.) and compared them to rice, maize and oat. The aneuploid stocks available in wheat are invaluable for comparative mapping because almost every DNA fragment can be allocated to a chromosome arm, thus preventing erroneous conclusions about probes that could not be mapped due to a lack of polymorphism between mapping parents. The orders of the markers detected by probes mapped in rice, maize and oat were conserved for 93, 92 and 94% of the length of Triticeae consensus maps, respectively. The chromosome segments duplicated within the maize genome by ancient polyploidization events were identified by homoeology of segments from two maize chromosomes to regions of one Triticeae chromosome. Homoeologous segments conserved across Triticeae species, rice, maize, and oat can be identified for each Triticeae chromosome. Putative orthologous loci for several simply inherited and quantitatively inherited traits in Gramineae species were identified.

on the location, the time period, and how measurements are taken. In the 1950s comprehensive studies using vis-Many cotton (Gossypium hirsutum L.) pollination studies have ual phenotypic traits reported 10% outcrossing in Texas been performed in the southern USA, but no data exist for California. In this study, we measured pollen-mediated gene flow (PGF) in four to 47% in Tennessee (Simpson, 1954; Simpson and Dundirections over 2 yr from herbicide-resistant source plots in upland can, 1956). These studies reported 28% outcrossing in cotton in the California cotton growing region and in a region with Mississippi, but a mean of 2% outcrossing was reported high pollinator activity. In addition, samples were taken from fields in similar locations in Mississippi 20 yr later (Meredith of conventional varieties at varying distances from fields planted with and Bridge, 1973). The authors suggested the differherbicide-resistant varieties to assess PGF under commercial producences were due to a reduction in wooded areas and the tion conditions. A seedling herbicide bioassay confirmed by DNA tests heavy use of pesticides resulting in a decrease in bee was used to measure PGF. PGF was independent of direction from pollinators. Also in Mississippi, Umbeck et al. (1991) the source plot and declined exponentially with increasing distance measured pollen transfer to non-transgenic rows of cotfrom 7.65% at 0.3 m to less than 1% beyond 9 m when there was high ton planted up to 25 m from a 4 ha field of cotton carpollinator activity. In the absence of high pollinator (honeybee, Apis mellifera L.) populations, PGF was less than 1% beyond 1 m. Pollen rying the nptII gene. PGF dropped below 1% at disflow in commercial fields was consistent with the experimental plot tances beyond 7 m, but continued to be detectable at a data, with only 0.04% PGF detected at 1625 m (1 mile). This study distance of 25 m in solid-seeded cotton. Studies sumconfirms that PGF decreases exponentially with distance in cotton marizing data (Ͼ15 000 samples) in Arizona, Arkansas, grown under California conditions and is low in the absence of polli-Mississippi, and North Carolina showed that PGF denators, although sporadic occurrence of PGF can be detected up to creased exponentially with increasing distance from the 1625 m.Published in Crop Sci. 45:1565Sci. 45: -1570Sci. 45: (2005.

A prerequisite for molecular level genetic studies and breeding in wheat is a molecular marker map detailing its similarities with those of other grass species in the Gramineae family. We have constructed restriction fragment length polymorphism maps of the A-, B-, and D-genome chromosomes of homoeologous group 3 of hexaploid wheat (Triticum aestivum L. em. Thell) using 114 F7-8 lines from a synthetic x bread wheat cross. The map consists of 58 markers spanning 230 cM on chromosome 3A, 62 markers spanning 260 cM on 3B, and 40 markers spanning 171 cM on 3D. Thirteen libraries of genomic or cDNA clones from wheat, barley, and T. tauschii, the wheat D genome donor, are represented, facilitating the alignment and comparison of these maps with maps of other grass species. Twenty-four clones reveal homoeoloci on two of the three genomes and the associated linkages are largely comparable across genomes. A consensus sequence of orthologous loci in grass species genomes is assembled from this map and from existing maps of the chromosome-3 homoeologs in barley (Hordeum spp.), T. tauschii, and rice (Oryza spp.). It illustrates the close homoeology among the four species and the partial homoeology of wheat chromosome 3 with oat (Avena spp.) chromosome C. Two orthologous red grain color genes, R3 and R1, are mapped on chromosome arms 3BL and 3DL.