Relationship between morphological and genetic differentiation in rice (Oryza sativa L.)

Indica and Japonica differentiation under the species of Oryza sativa L. ha s been documented using morphological characters, isozyme and DNA markers. We illustrate marker assisted analysis of genetic differentiation with a sa mple of RFLP and isozyme data from 111 accessions of rice lines and compare it to morphological differentiation based on Cheng and Wang' morphological character index. The results lead to three main conclusions: (1) Among the 92 polymorphic cloned probes deliberately selected, 41 were highly associa ted with Indica-Japonica differentiation, suggesting such differentiation w as an accumulative process of gene change at multiple loci; (2) There exist two main types of relationships between morphological and genetic differen tiation. For well differentiated Indica and Japonica (as the case in the co ntrol subset), morphology and genomic constitutions are synchronously speci alized. For incompletely differentiated rice lines (as the case in the subs et of DH lines), morphological differentiation and genetic differentiation are asynchronous. (3) Synthetic or incompletely differentiated rice lines w ith different genomic constitutions are often adapted to specific environme nts. These results indicate that marker alleles provide applied breeders wi th effective ways to identify, track, and incorporate regions of chromosome s governing adaptedness to specific target environments into improved culti vars.