QTL mapping for crude protein and protein fraction contents in rice (Oryza sativa L.)

Improvement of rice storage proteins is important in rice breeding for high nutritional quality. Seventy-one recombinant inbred lines (RIL) derived from a cross between japonica variety Asominori and indica variety IR24 were used to study the inheritance of crude protein and protein fraction contents in rice. A total of 16 QTL were identified and mapped on eight chromosomes. Several QTL affecting contents of different protein fractions were mapped in the same chromosomal region. In particular, two QTL with a significant contribution were identified to simultaneously affect prolamin and glutelin contents. One QTL denoted as qCP-12 affecting crude protein content (CP) was located in the same region as QTL qGLT-12 affecting glutelin content, in agreement with the positive correlation between glutelin level and protein content. QTL with larger genetic effects were further confirmed using two sets of chromosome segment substitution lines (CSSL), where Asominori and IR24 were used as the recurrent parents. By QTL comparative analysis, two QTL for CP, three for globulin content and one for prolamin content were located in the vicinity of CP QTL previously identified in polished rice. Application of these results in rice breeding is discussed.