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K. Nagaki, H. Tsmjimoto & T. Sasakuma (Kihara Inst. Biol. Res., Yokohama City Unvi.)
The repetitive sequences in wheat and barley

Synteny maps of Triticeae species indicated that the structures of these genomes are well conserved. We here analyzed the repetitive DNA sequences in these species, especially in wheat and barley. Afa family repetitive sequence that was originally isolated as the D genome-specific sequence (pAs1; Rayburn and Gill, 1988) was found in all the Triticeae species investigated. The molecular evolutionary studies of the sequences clearly showed that amplification events took place relatively suddenly using a single unit as the master of amplification. One clone including sub-family sequence of barley could be a good chromosome marker to identify each barley chromosome just like a clone pAs1 is a good marker for the wheat D genome chromosome identification.

S. Taketa & K. Takeda (Res. Inst. Bioresources, Okayama Univ.)
Cytogenetical analysis of wheat-barley hybrids

Bread wheat cultivars were crossed as the female parent with cultivated barley (Hordeum vulgare) and wild barley (H. spontaneum). Some barley accessions showed enhanced crossability with bread wheat. Variation in the patterns of chromosome elimination in the hybrids was recognized. Some morphological marker genes of the barley parent expressed their characteristics in the hybrids. All barley chromosome 5 so far tested caused sterility when introduced to bread wheat. A cytogenetical scheme to remove this sterility factor(s) are proposed. A partial amphiploid between bread wheat and barley, which carries all barley chromosomes except chromosome 5 in disomic condition (2n=54), was successfully produced.

T. Sasanuma (Fac. of Agric., Kyoto Univ.)
Analysis of the small subunit of ribulose-1,5-bisphosphate carboxylase (rbcS) multigene family in the tribe Triticeae

To study the evolution of multigene family in plants, rbcS was chosen. Fifteen species of the Triticeae and its relative tibes were analyzed. The sequences were classified into three types (a, b and c) based on the differences in the intron. Triticum and Aegilops species have both a and b types. The c type was found only in Agropyron. The difference between a and b types was larger than the interspecific difference within each type. It was concluded that the differentiation of a and b types of rbcS occurred before the formatrion of Triticeae.

M. Murata (Res. Inst. Bioresources, Okayama Univ.)
Attempts to clone alien chromosome-specific genes in wheat (Triticum aestivum)

Wheat has large genome size (16,000 Mb/haploid), more than 100 times as much as that of Arabidopsis thaliana (145 Mb/haploid), and also involves a large proportion of repetitive DNA sequences in the genome. These make it difficult to isolate wheat genes by the strategies that are being commonly used in A. thaliana and other plant species. By using genomic subtraction, we attempted to isolate genes from the midget, chromosome in a common wheat with rye cytoplasm. However, repetitive DNA and rye-chloroplast DNA were preferentially cloned, and no low-copy sequences were obtained. We also applied the differential screening to identify rye- specific cDNA in the wheat strain carrying the midget chromosome, since it has been shown that the midget chromosome had originated from rye. Almost all cDNAs screened by this strategy were those corresponding to the photosynthesis-related genes such as rbcL, rbcS, and cab. Other few cDNAs showed rye-specificity, but their functions are unknown.

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