[Effects of different varieties and sowing dates on development stages of wheat]

The effects of different sowing dates and varieties on development stages of wheat were studied in this paper. The results showed that the emergence of tiller was mainly regulated by the ecological factors rather than the genetic effect. For winter-type variety(Jing 411), most variable growth duration throughout the entire growth cycle occurred from tillering to jointing. In contrast, the timing of single ridge stage was determined by genotypic effect rather than ecological factors. Single ridge to double ridge stage was most sensitive to vernalization progress. For spring sowing of winter-type variety, the vernalization process could last till floral primordium differentiation stage. The corresponding relationships existed between phenological and spike development stages in different sowing dates, although a little variable. Winter-type variety had more ecologically variable leaf primoudia, due to its stronger vernalization requirement. For winter-type variety, the primordium numbers of reproductive organs were not apparently related to the GDD accumulated prior to vernalization completion, while for spring-type variety(Yangmai 158), the numbers of different apex primordia including vegetative and reproductive organs were significantly related to the accumulated GDD during the entire phenological stages as well as before anther separation stage.