Interspecific Hybridizing Between Lagerstroemia Indica And L.Caudata

Crape myrtle (Lagerstroemia indica) is an import flower tree in summer in China and it has been widely applied in recent years, but the lack of low plant type, fragrant flowering, early flowering varieties of crape myrtle affects the extensive application of the crape myrtle. L. caudata is native to China, it’s early flowering and fragrant flowering, so it’s an excellent material for cultivating fragrant flowering and early flowering varieties of crape myrtle. This study established such a objective to breed new varieties wcrape with various type, bright colors, fragrant flowers and early flowerin and in order to reach the goal, the study took four dwarf crape myrtle varieties and L. caudate as parents to do interspecific hybridizing. And all of the hybrids’morphological and molecular identification was done. In addition, Fl hybids, which had been obtained from cross-breeding between L. indica and L. caudata, were used to inbred and back-cross to improve characteristics of itself. At the same time, the characteristics of flowering, pollination biology, and pollen of L. caudata was studied. The main findings were as follows:1. Cross-breeding between L. indica and L. caudate and harvesting the F1 offsprings4 cultivars of L. indica with low plant, brightly colored flowers and large flower diameter were chosen to make Orthogonal and reciprocal crosses with L. caudata, there were 8 crosses,1344 flowers were pollinated, and 950 fruits, about 23750 seeds and more than 6000 hybrid seedlings were obtained. It had been found experimentally that it was easy to obtain interspecific hybrids between L. indica and L. caudata, but seed germination rate of some combination was low. The result of morphological and molecular identification to hybrids showed that all of the hybrids are real.2. The characteristics of flowering and pollen of L. caudata was studied.L. caudata planted in Beijing flowers in the last ten days of May and the flowers came into terminal florescence in the last ten days of June. But the florescence of L. caudate could be prolonged to July by pruning. The Petals of L. caudata expanded at 6:00am, then at 6:30 am pollen spread with anther dehiscence and the stigma of L. caudata secreted a large number of mucous. The combination, which made highest pollen germination rate, was sucrose 150g/L + H3BO3 30mg/L+ CaC12 30mg/L+150g/LPEG4000, sucrose had a great effect on pollen germination, next came H3BO3 and PEG4000. The time to keep pollen activity was different in various condition,4℃dry environment was the best one to keep pollen of L. caudate by contrast.3. Some genetic character analysis of F1 from cross-breeding between L. indica and L. caudata were improved.Genetic character of F1 from cross-breeding between L. indica and L. caudata was analyzed in flower colour, flower diameter, florescence and flower fragrance.The result showed that hybrids from 6 combinations had white or purple flowers mostly, and neither of the parents had purple flowers.The flower diameter of hybrids was between mather and father. However seven of hybrids from L. caudataxL. indica’Qiao Jia Ren’had larger flower diameter than parents.All of the hybrids flowered earlier than L. indica, but still later than L. caudata,besides they all had fragrant flowers except two from L. caudataxL. indica’Qiao Jia Ren’.4. Using F1 to inbred, back-cross, triple-cross and harvesting the F2 offspringsIn order to get fragrant flowering varieties of crape myrtle, F1 was used as experimental material to inbred, back-cross with L. caudate, more than 3400 of F2 offsprings were harvested. The results showed that it’s hard to obtain inbred hybrids from F1, it should be possibly caused by self-incompatibility. On the contrary, seed setting rate of back-cross of F1 was high, but seeding rate was low. By measurement, hybrids from back-cross were real.In summary, this study got F1 and F2 seedings, which came from cross-breeding between L. indica and L. caudate, and seedings from back-cross. Through the studies on interspecific hybridizing between L. indica and L. caudata, it laid the foundation for obtaining the new cultivars of L. indica with low plant type, fragrant flowering, early flowering and brightly colored.