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

Indica and Japonica differentiation under the species of Oryza sativa L. has been documented using morphological characters, isozyme and DNA markers. We illustrate marker assisted analysis of genetic differentiation with a sample 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 associated with Indica-Japonica differentiation, suggesting such differentiation was an accumulative process of gene change at multiple loci; (2) There exist two main types of relationships between morphological and genetic differentiation. For well differentiated Indica and Japonica (as the case in the control subset), morphology and genomic constitutions are synchronously specialized. For incompletely differentiated rice lines (as the case in the subset of DH lines), morphological differentiation and genetic differentiation are asynchronous. (3) Synthetic or incompletely differentiated rice lines with different genomic constitutions are often adapted to specific environments. These results indicate that marker alleles provide applied breeders with effective ways to identify, track, and incorporate regions of chromosomes governing adaptedness to specific target environments into improved cultivars.