Study On Cross Compatibility Of Rhododendron L.

The genus Rhododendron, the family Ericaeae, is the famous ornamental flowers in theworld, and is one of the ten Chinese traditional flowers as well. Chinees Rhododendron is of richresources, but breeding process is slow.Making full use of Rhododendron resources in China, forgermplasm creation, is of great significance to promote national azaleas industry development.Therefore, in this paper conducted the following researchs: Firstly, this reserch was conductedwith the pollens grains of Rhododendron ciliatum, R. polylepis, R. taronense, R. simsii, R. ovatum,and R. hybridum. The effects of sucrose, H3BO3and CaCl2single factor and orthogonal test L25(53) on Rhododendron pollen germination were investigated. The I2-KI, TTC, benzi-dine-H2O2,and MTT methods were compared to find the fastest determination method of Rhododendronpollen vitality. The effection of drying time on pollen germination of R. oratum and differentpreservation temperature and unfreeze method on pollen germination of R. taronense, R. delavayi,R. ciliatum were tested, based on that results low tempreture storge of3kinds of Rhododendronwas conducted. Finally, R. simsii, R. pulchrum and R.ovatum were used as maternal parent, foursubgenus21species of Rhdodendron of were used as male parent to conduct interspecifichybridization. Fluorescence microscopy was used to observe pollen tube growth situation,number of fruit set and seeds per fruit were counted, and analysed compatibility of each hybridcombination. This research leads to the conclusions as follows:(1) Sucrose, H3BO3, CaCl2and interaction of3factors have great effects on the germinationof Rhododendron pollen.The optimal culture medium of pollen germination of R.ciliatum, R.simsi,R.ovatum and R.hybridum were respectively sucrose100g L-1+H3BO30mg L-1+CaCl250mg L-1; sucrose150g L-1+H3BO30mg L-1+CaCl250mg L-1;sucrose50g L-1+H3BO3200mg L-1+CaCl20mg L-1and sucrose150g L-1+H3BO3100mg L-1+CaCl20mg L-1.The optimumand rapid staining method to determine pollen vitality of Rhododendrons was MTT.(2) The results of pollen drying and low-temperature storage show that: R.ovatum pollenwas not suiTab. for drying, the low temperature for Rhododendron storage was-20℃, the waterat37℃was suiTab. for pollen thawing. Long term low-temperature storage shows that: therewas a significant difference among different species.(3)11out of13combanations and174ovaries was obtained when R. Simsii as maternalparent, each one of these combinations acquired hybrid seeds, its hybridization affinity withinSubgenus Tsutsusi was better, but there was a significant difference of intersubgenerichybridization affinity among different cross combination.9out of13combanations and174ovaries was obtained when R. pulchrum as maternal parent, only3of these combinationsacquired hybrid seeds. The optimal embryo age for embryo rescue was different fromcombinations.(4) Male parent pollen attached and germinated on stigmas of R.simsii and R.pulchrum forall combinations, only a few pollens attached and germinated on stigmas of R.ovatum forindividual combinations, the situation of pollen tube growth varies among different male parent.R.simsii had better affinity as female parent, R.pulchrum and R.ovatum took second and thirdplace. The closer phylogenetic relationships, the cross compatibility were better, intersubgenuscross compatibility varies among different male parent.