Androgenic haploids: factors controlling development and its application in crop improvement

Androgenesis in flowering plants is a unique biological process. It provides an understanding of the biological basis of single-cell microspore embryogenesis to the production of a dihaploid plant. This system provides an unparalleled opportunity to shorten the breeding cycle and fix agronomic traits in the homozygous state, such as recessive genes for disease resistance. The most desirable dihaploid variation in all the major crops including rice, wheat, barley, maize, rape, cotton, sun-flowe, coffee, etc. has already been developed and util-ized in modern crop breeding. Many known and a few unknown factors are involved in such development. A few noteworthy factors are donor plants, genotypic variation, media composition, and handling of cultures, which may have a greater influence on the response of androgenesis. A further opportunity has arisen to use a pollen-specific gene, promoter and transgenic dihap-loid (homozygous), gene expression, proteomics, trans-lational regulation and post-translational modification of genes to widen the scope of crop improvement. The homozygous (isogenic) lines will provide unique genetic material for mapping populations for use in functional genomics and molecular breeding