Genetical study on the grain characters by the use of molecular markers in rice [Oryza sasiva] (preliminary report)

As a basis of rice breeding for grain characters including morphology and composition, the authors dealt with an estimation of quantitative trait loci (QTL) by suing molecular markers such as RFLP and RAPD. 1) In order to measure the amount of polymorphism of RFLP markers detected among the parental lines, twelve rice lines belonging to indica, japonica and American testers were assayed with the combinations between 53 RFLP markers and two restriction enzymes. Genetic variation was detected for 44 (41.5%) out of 106 probe-enzyme combinations. A high degree of polymorphism (40% and 43%) was indicated with HindIII or EcoRI, confirming the previous results that these enzymes are suitable for RFLP analysis in rice. 2) Frequencies of polymorphism detected between American testers ranged from 9.4% to 32.1% suggesting the existence of fairly large genetic variabilities. On the other hand, japonica lines were closely related showing an extremely low frequency of polymorphism. RFLP diversity between Surjamkhi (indica) and japonica or American lines was over 20%, while those between japonica and American lines indicated a variation ranging f rom 5.7% to 34% in the combination with different japonica lines. 3) Genetic variations of grain characters are also important for choosing parental combinations for the crossing experiments. Rice lines tested were classified into three categories based on grain size: Kirara 397, ID-47, No.56, 83N1072, 83N1154 and 83N1209 belonging to "short grain" type; 83N1038, 83N1168 and IRAT13 belonging to !large grain" type; and the remainders belonging to "long and slender grain" type. Three American testers (83N1038, 83N1202 and 83N1209), and an indica line (Surjamkhi) showed high amylose content, whereas all japonica lines (Kirara 397, ID-47, IRAT13 and No.56) and an American tester (83N1154) fell into a group showing low or none amylose content