Institute of Crop Breeding and Cultivation, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Due to the irregular segregation of chromosomes during meiosis of autoploids
the microspores with different chromosome number are produced. Therefore,
different aneuploids are obtained among plants derived from anther culture.
A research program on the anther culture of autotetraploid rice was initiated in 1984 to identify the breeding lines with special traits. In the combinations inoculated in 1987, we discovered a group from one callus with a very high capacity for propagation, fast growth and good synchronizaiton. This material has been subcultured for 30 generations during more than one year and still continues to show these good characters.
In order to analyze the propagation capacity of this material, we inoculated small calli containing 1-20 buds to 100 ml triangle flasks. These buds multiplied at an average rate of 150-200 times, and some as much as 350 times per month. Furthermore, the multiplication rate was higher if more buds existed in the callus. A month's culture of three bottles of calli (each containing a callus cluster with 20 buds) is enough to produce 10,000 buds.
We also observed the morphological changes during propagation. 7-20 days after the buds were transferred into new differentiation medium, many white transparent protrusions like calli appeared around the tips of buds. These protrusions were judged to be the bud primordia under stereomicroscope. They soon transformed into buds and became green, and almost simultaneously there were again white protrusions produced around the new buds and these new buds again produced buds. After 20 days of culture a hemisphere of bud clusters was formed in the bottle and also the roots emerged.
When the bud were cut into fragments and inoculated on the MS dedifferentiation medium, calli were induced again. When these calli were transferred to the MS differentiation medium, half of them could differentiate the buds and still had the capacity to propagate rapidly.
A large number of intact plantlets were produced within one month when the bud clusters were cultured under a conditions of 28 degrees C and long days. In the spring of this year we planted a large number of plantlets in the field. Most of them grew well and looked normal. However, a small number of variant plants with narrow, dark green leaves or wide, light green leaves appeared.
We feel this material can be used for isolating the protoplasts or it may serve as a material for screening for stress resistance or as a vector for the transfer of exogenous genes in the genetic and breeding researches.