Because of the huge size of the common wheat (Triticum aestivum L., 2n ϭ 6x ϭ 42, AABBDD) genome of 17,300 Mb, sequencing and mapping of the expressed portion is a logical first step for gene discovery. Here we report mapping of 7104 expressed sequence tag (EST) unigenes by Southern hybridization into a chromosome bin map using a set of wheat aneuploids and deletion stocks. Each EST detected a mean of 4.8 restriction fragments and 2.8 loci. More loci were mapped in the B genome (5774) than in the A (5173) or D (5146) genomes. The EST density was significantly higher for the D genome than for the A or B. In general, EST density increased relative to the physical distance from the centromere. The majority of EST-dense regions are in the distal parts of chromosomes. Most of the agronomically important genes are located in EST-dense regions. The chromosome bin map of ESTs is a unique resource for SNP analysis, comparative mapping, structural and functional analysis, and polyploid evolution, as well as providing a framework for constructing a sequence-ready, BAC-contig map of the wheat genome.

A total of 1918 loci, detected by the hybridization of 938 expressed sequence tag unigenes (ESTs) from 26 Triticeae cDNA libraries, were mapped to wheat (Triticum aestivum L.) homoeologous group 4 chromosomes using a set of deletion, ditelosomic, and nulli-tetrasomic lines. The 1918 EST loci were not distributed uniformly among the three group 4 chromosomes; 41, 28, and 31% mapped to chromosomes 4A, 4B, and 4D, respectively. This pattern is in contrast to the cumulative results of EST mapping in all homoeologous groups, as reported elsewhere, that found the highest proportion of loci mapped to the B genome. Sixty-five percent of these 1918 loci mapped to the long arms of homoeologous group 4 chromosomes, while 35% mapped to the short arms. The distal regions of chromosome arms showed higher numbers of loci than the proximal regions, with the exception of 4DL. This study confirmed the complex structure of chromosome 4A that contains two reciprocal translocations and two inversions, previously identified. An additional inversion in the centromeric region of 4A was revealed. A consensus map for homoeologous group 4 was developed from 119 ESTs unique to group 4. Forty-nine percent of these ESTs were found to be homoologous to sequences on rice chromosome 3, 12% had matches with sequences on other rice chromosomes, and 39% had no matches with rice sequences at all. Limited homology (only 26 of the 119 consensus ESTs) was found between wheat ESTs on homoeologous group 4 and the Arabidopsis genome. Forty-two percent of the homoeologous group 4 ESTs could be classified into functional categories on the basis of blastX searches against all protein databases. G ENOME analysis has been used to establish the hexaploid wheat (Triticum aestivum L.). Each of the 21 evolutionary and homoeologous relationships of chromosomes has been identified and characterized by the three genomes (AA, BB, and DD) that make up Sears (1954Sears ( , 1966 with respect to genomic and homoeologous relationships. There is a high degree of colin-1 Present address: Plant Breeding and Acclimatization Institute,

A total of 944 expressed sequence tags (ESTs) generated 2212 EST loci mapped to homoeologous group 1 chromosomes in hexaploid wheat (Triticum aestivum L.). EST deletion maps and the consensus map of group 1 chromosomes were constructed to show EST distribution. EST loci were unevenly distributed among chromosomes 1A, 1B, and 1D with 660, 826, and 726, respectively. The number of EST loci was greater on the long arms than on the short arms for all three chromosomes. The distribution of ESTs along chromosome arms was nonrandom with EST clusters occurring in the distal regions of short arms and middle regions of long arms. Duplications of group 1 ESTs in other homoeologous groups occurred at a rate of 35.5%. Seventy-five percent of wheat chromosome 1 ESTs had significant matches with rice sequences (E Յ e Ϫ10 ), where large regions of conservation occurred between wheat consensus chromosome 1 and rice chromosome 5 and between the proximal portion of the long arm of wheat consensus chromosome 1 and rice chromosome 10. Only 9.5% of group 1 ESTs showed significant matches to Arabidopsis genome sequences. The results presented are useful for gene mapping and evolutionary and comparative genomics of grasses. W HEATS are the universal cereals of Old Worldi.e., hexaploid bread wheat (Triticum aestivum L., 2n ϭ agriculture (Harlan 1992) and belong to the 6x ϭ 42) and tetraploid durum-type wheat (T. turgidum world's foremost crop plants (Feldman et al. 1995; Nevo L., 2n ϭ 4x ϭ 28). Bread wheat is most important and et al. 2002). Wheat is one of the most widely cultivated contains three genomes: A, B, and D (Sears 1969). food crops and is the staple food in Ͼ40 countries andThe genome size of hexaploid wheat is the largest for over 35% of the global population (Williams 1993

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To evaluate the extent of the genetic change and its effects on the seed protein composition of soybean cultivars released during the past 60 years, representative ancestral cultivars and those derived from selective breeding were grown in a side-by-side comparison. Total seed protein content, determined by combustion analysis of nitrogen, revealed a decline in the protein content after decades of selection and breeding. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis comparison of protein profiles of the soybean cultivars indicated that relative expression of most of the seed storage proteins had not varied substantially from the ancestral lines to the present commercial cultivars. There was noticeably less beta-subunit of beta-conglycinin, a protein devoid of sulfur amino acids, in the modern cultivars represented by Mustang, Pioneer 93B09, and Asgrow 3602. Comparison of the amino acid profiles of soybean seed, a benchmark of the protein's nutritional quality, revealed that the ancestral progenitor, G. soja, was significantly higher in cysteine, glutamic acid, histidine, and arginine than either the ancestral or the modern cultivars. Selective breeding over the past 60 years minimally affected the overall amino acid composition. The degree of divergence in the DNA sequence of the genes encoding glycinin and beta-conglycinin in the ancestral and modern cultivars was investigated using Southern hybridization and the polymerase chain reaction. Even though some restriction fragment polymorphisms could be detected, overall, the banding patterns were remarkably similar among the ancestral cultivars and those derived from them, suggesting a high degree of conservation of seed-storage protein genes. The results of our study suggest that selection and breeding for yield during the past 60 years had no major influence on the protein composition, ostensibly because of limited genetic diversity among the parental lines.