Duplications of DNA in 5 and 6 Barley Chromosomes and its Influence on Plant Reproduction
Genetic studies of naturally existing genomes of higher plants showed frequently occurrence of duplication of genetic material. Because the investigations on the genetic structure of naturally existing genomes point out the significance of duplications for the evolutionary process of genotype, but do not describe the influence of newly occurring duplication on the function of the whole genome, such studies were undertaken at present since chromosome engineering techniques make it possible to produce duplication of chromosome segments of different size. Duplications of spring barley (cv. Bonus) 5 and 6 chromosome DNAs were produced as a result of recombination of five selected T5-6 reciprocal translocations with known breakpoints positions. The cytological examination of F2-progeny showed the origination of five duplications (maintained as lines D204 ? D208) with different size of duplicated segment of 5L and 6L chromosome arm. In percentage of general length of 5 and 6 barley chromosomes the relative size of duplications fixed in particular line was: D204 - 26.7%, D206 ? 23,5 %, D207 ? 19,1 %, D205 ? 18,4 %, D208 ? 7,4 %. Lines D205, 206, 207 and 208 shoved homozygotic duplications and were fertile. Line D204 carried duplications in heterozygotic condition (in one of homologic chromosome) and there was no viable of such homozygote in all analysed seed of F2-progeny. This type of homozygotic genotypes were established in F3-generation developed as a progeny of heterozygotic plants of D204 line, but their frequency differ with high statistical significance from theoretical distribution (x2=12.341**).
Barley plants with the duplicated segment of 5L chromosome arm between "v" and "o" translocation breakpoint positions were fertile and produced seeds with normal germinability. Duplication of the segment from "v" to "p" translocation breakpoints caused a drastic reduce of seed setting. Pollen morphology examinations and screening of enzyme activity showed that limited pollen functionality could be the main reason of this residual fertility. The completed data about seeds germinability and seedlings development showed that in 5L chromosome arm between "o" and "p" translocation breakpoints there is a gene(s) of which duplication resulted in a plant sterility, functioning most probably as a mortality of zygotes (or embryos) on different step of plant development.
As it was shown on the example of artificial synthesis of duplications in 5 and 6 barley chromosomes, formation of intragenomic duplications yielded both in originating of new stress-tolerance adaptation as well as in defects of reproduction ability.
T. Sodkiewicz, W. Sodkiewicz, A. Hagberg1
Institute of Plant Genetics, Polish Academy of Sciences,