Factors Determining Genotypic Variation in the Speed of Rice Germination

Rapid germination is important for both direct seeded rice in the field and for the production of germinated brown rice for healthy food. This study aims to evaluate genotypic differences in germination speed and identify characteristics that determine germination speed. Seven experiments were conducted to determine (i) the impact of dehulling on water absorption and germination, (ii) variety consistency in germination speed across crops grown in three years, and (iii) the effect of grain size. Germination speed in both paddy rice and dehulled brown rice was significantly correlated with grain moisture content at early stages of soaking, however significant interaction of genotype and grain type (paddy and brown rice) existed and varieties differed in their response to dehulling. Germination speed of grain from crops exposed to water deficit in the field was slightly slower than those with higher water supply. Sherpa/IRAT109 genotypes with smaller grain size tended to germinate faster than larger grain, however no significant effect of grain size existed among diversity set varieties. It was concluded that genotype ranking in germination speed was consistent across years and water availability conditions, and that barriers to water absorption in hull and pericarp were important determinants of germination speed. The existence of genotypic variation in germination speed has management implications for both field crop establishment and paddy germination in food processing.