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Abstract. The quality of barley for the range of end uses from animal feed to brewing is determined by many genes, making the breeding of new barley varieties difficult. Understanding of the molecular basis of barley quality has been advanced by biochemical studies. More recently, molecular genetic tools are allowing the analysis of the biochemical factors contributing to grain quality. Many genetic loci influencing key quality attributes have been identified by gene mapping. Limited success has been reported in using this information to select for quantitative trait loci for these quality traits in plant breeding. Genomic techniques allowing more detailed analysis of variations in the barley genome in relation to quality promise to extend significantly the value of molecular genetic approaches to barley quality improvement. Definition of the genetic basis of malting quality requires the identification of the genes involved in germination and endosperm modification. Feed quality remains difficult to define. Recent advances are likely to accelerate the rate of discovery, providing new options for analysis of barley quality.

This chapter compares the components and structures of dicotyledon cell walls, monocotyledon cell walls, Peridophyte cell walls and gymnosperm cell walls. The evolution of cell walls is described.

In this chapter some of the salient features of polyploidy in plants, including a brief description of its prevalence and modes of formation are discussed. Several model systems are presented for the study of polyploids and provide example case studies, hoping to illuminate how the 'internal' and 'external' processes associated with polyploidy contribute to evolutionary success and to the generation of biodiversity.

Empirical studies have shown that an inverse relationship exists between primer site conservation and evolutionary relationship between test taxa, with the threshold distance after which no amplification can be expected being lower in plants than in animals. However, there is still an insufficient number of studies investigating the use of heterologous SSR primers in plants. The current understanding of interspecific amplification of microsatellites in plants is the main focus of this chapter.