Nuclear DNA content of ten rice species as determined by flow cytometry

Accurate estimations of nuclear DNA content of rice are important because this crop is being used in many types of molecular studies. The main objective of this study was to estimate the nuclear DNA content in ten rice species by flow cytometry. Most of the values obtained were lower than those obtained in earlier studies using Feulgen microdensitometry. Significant differences in genome size among rice species were found. Oryza glaberrima had the smallest genome (0.73-0.76 pg/2C), while O. minuta and O. latifolia had the largest values (ca. 2.33 pg/2C). Tetraploid species had more nuclear DNA than diploid ones. The AA genome had less DNA (0.86-0.96 pg/2C) than the CC (1.14-1.17 pg/2C) and EE (1.99 pg/2C) genomes. The AA genome of O. saliva was larger than the AgA g genome of O. glaberrima and the A1A 1 genome of O. longistaminata, which had mean values of 0.73-0.76 and 0.78 pg/2C, respectively. Indica (IR36) and japonica (Yukihikari) cultivars of O. saliva also showed significant differences. Three different nuclear DNA levels (1.93, 1.85, and 1.31 pg/2C) were found among five O. ridleyi plants analyzed. Flow cytometry also allowed rapid and reliable determination of the ploidy level of anther culture-derived plants.