Use of an Acrocentric Chromosome in a Genetic and Linkage Study of Barley Chromosome 4.

Barley (Hordeum vulgare L.) is one of the major and most frequently used crop plants in genetic studies (Hockett and Nilan 1985, Ramage 1985).Seven linkage groups were initially established mainly by conventional linkage analysis (Robertson et al. 1965) , and with extensive use of reciprocal translocation analysis as well as conventional analysis (Burnham and Hagberg 1956, Ramage 1985).Aneuploid analysis has proved very useful in genetic and linkage studies in barley (Tsuchiya 1991).By means of primary trisomic and telotrisomic analysis many genes have been associated with their respective chromosome or chromosome arms, and in locating centromere position in linkage maps (Fedak et al. 1971, 1972, Tsuchiya and Singh 1982).Linkage maps will be more useful if genes are physically located.In this regard structural changes in chromosomes such as translocations, inversions, and deficiencies have been used along with pachytene analysis to position genes on chromosomes of several species such as maize and tomato.Although the long chromosomes of barley at the pachytene stage are not suitable for pachytene studies, acrotrisomics in which the extra chromosome carries deficiencies for different segments of chromosome arms, can be used in the physical localization of several marker genes in specific chromosome arms.In this study acrotrisomic 4L4S was utilized to physically locate several marker genes on the chromosome arms.The effects of the extra chromosome on morphology, cytology, and breeding behavior were also studied.