Why is the sub-population structure of rice important for breeding?
O.sativa is composed of at least five genetically identifiable sub-populations, and there is sub-population structure in O. rufipogon as well. Some sub-populations are more closely related than others and the genetic distance between sub-populations can be used to predict both the frequency of obtaining transgressive segregation among the progeny of a cross, and to predict the likelihood of encountering fertility problems in distant crosses. A majority of the world’s rice is produced from inbred (pure line) varieties and historically, inbred variety development has focused almost exclusively on crosses between members of the same sub-population (indica X indica) or between related sub-populations (i.e., tropical japonica X temperate japonica). This is largely due to the prevalence of sub-population incompatibilities that lead to sterility and make it difficult to obtain a random array of fertile recombinants from indica X japonica crosses.
A majority of the world’s rice is produced from inbred (pure line) varieties and historically, inbred variety development has focused almost exclusively on crosses between members of the same sub- population (indica-indica) or between related sub-populations (i.e., tropical japonica x temperate japonica). This is largely due to the prevalence of sub-population incompatibilities that lead to sterility and make it difficult to obtain a random array of fertile recombinants from indica-japonica crosses.
