Abstract
Molecular analyses and present distribution of wild and weedy populations as well as recent archaeological findings suggest that azuki bean has been domesticated first in Japan. Comparative genomic analyses for azuki bean, rice bean, mungbean, and black gram revealed genetic background for major domestication traits, i.e., (A) seed size, (B) pod dehiscence, and (C) water absorption by seeds. The increase of seed size is a genetically complex process and attained by mutations of at least 5 to 7 genes, and the loss of pod dehiscence has simply attained by mutations of 1 or 2 genes for a given species, while the loss of dormancy and/or water absorption by seed is brought by mutations on different numbers and sets of genes among beans. Recent identification of domestication genes and studies on associated changes of phenotypes among beans are discussed. Most changes of domestication traits revealed are due to loss-of-function mutations, which have been selected by farmers. This might explain the reason why domestication could occur rapidly compared with evolution. Based on these findings, we try to develop a new crop by inducing artificial loss-of-function mutations on domestication genes of stress tolerant wild species. This plant breeding strategy is named “Neo-domestication”.
