Domestication, Polyploidy and Genomics of Crops

About half of all higher plant species are recognizable as polyploids, a major feature of genome architecture where there are more than two sets of chromosomes. Advantages include multiple copies of each gene with different regulation, so essentially fixing heterosis; larger cell size; and the opportunity for mutation without lethality. Disadvantages include twice as much DNA to replicate; incorrect control of multiple gene copies in interacting genomes; chromosome instability at mitosis; and the challenges of ensuring chromosome pairing and regular meiotic segregation in seed crops, in breeding hybrid materials, or else combining sterility with parthenocarpy in fruit crops. Given these substantial contrasts, it is perhaps surprising that the top three cereal crops are wheat (a modern hexaploid 2n=6x=42), rice (diploid, 2n=2x=14), and maize (palaeotetraploid, 2n= 2 or 4 x =20), suggesting neither advantages nor disadvantages are overwhelming. I will consider the balance of positives and negatives over evolutionary and crop-breeding timescales. In the second part of my talk, I will consider how knowledge of polyploid behaviour and knowledge of ancestors can be exploited, discussing our work with polyploids, both well-known (wheat, Brassica, banana) and less known (proso millet, ornamentals and saffron crocus).

Further details and references will be at www.molcyt.com. Email phh(a)molcyt.com