This study was carried out to establish a systematic hybridization method and to obtain informations on inheritance of several important characters in Rose of Sharlon, Hibiscus syriacus L.. Hybridization was made between representative 10 varieties and the total number of crosses was thirty including reciprocal hybridization. We observed crossability, germination rate of hybrid seeds, survival rate of hybrid progenies in each cross. And we checked pollen viability, pollen tube elongation, the number of ovule and embryogenesis to study the factors affecting seed setting.
The capsule setting rate and the number of seeds per capsule was ranged 0 - 94% and 0 - 29.8, respectively. The germination rate of hybrid seeds and the survival rate was ranged 5.2 - 92.6% and 50 - 100%, respectively. Based on these results we caculated the plant number per hybridization, in some crosses I5 plants could be obtained while in some other cases zero.
There was no difference in the ovule number between cultivars, while pollen viability was greatly different. It seemed that pollen tube elongation was affected by pollen viability and self-incompatability gene. In the cross whose pollen tube growth was normal but having a low seed setting rate, embryos were aborted around 6 days after fertilization.
Based on above results we proposed that crossability and seed development were affected by pollen viability, self-incompatibilty and embryo abortion. And it seemed that genetic incongruity between parents resulted in hybrid breakdown during the seedling stage. It was thought that the above-mentioned factors could act as an abstacle in the hybridization breeding.
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