Role of model plant species.

The use of model or reference species has played a major role in furthering detailed understanding of mechanisms and processes in the plant kingdom over the past 25 years. Species which have been adopted as models for dicotyledons and monocotyledons include arabidopsis and rice and more recently brachy-podium,Such models are diploids, have few and small chromosomes, well developed genetics, rapid life cycles, are easily transformed and have extensive sets of technical resources and databases curated by international resource centres. The study of crop genomics today is deeply rooted in earlier studies on model species. Genomes of model species share reasonable genetic synteny with key crop plants which facilitates the discovery of genes and association of genes with phenotypes. While some mechanisms and processes are conserved across the plant kingdom and so can be revealed by studies on any model species,others have diverged during evolution and so are revealed by studying only a closely related model species.Examples of processes that are conserved across the plant kingdom and others that have diverged and therefore need to be understood by studying a more closely related model species are described.