Relationship Between Leaf Characteristics and Photosynthetic Capacity of Hybrid Progenies of Different Hybrid Combinations of Catalpa fargesi

The trial with 2 years old seedlings of a hybrid combination of Catalpa fargesi as the female parent, Catalpa bungei, Catalpa fargesii and Catalpa fargesi as the male were used as materials. The differences of leaf traits and photosynthetic characteristics of different hybrid combinations of C. fargesi were compared and analyzed. The leaf characteristics, chlorophyll content and photosynthetic characteristics were determined respectively. The results showed that there were significant or extremely significant differences in leaf traits and photosynthetic performance indexes among different hybrid combinations of C. fargesi. The coefficient of variation and repeatability of leaf area were higher, and the specific leaf weight was the lowest. The genetic variation of leaf area was higher than other indexes. The variation trend of leaf characters of different male parent combinations was C. fargesii > C. bungei > C. fargesi. The photosynthetic capacity, leaf area and chlorophyll content of interspecific crossing species between C. fargesi were higher than those of intraspecific hybridization. The maximum net photosynthetic rate and leaf area of the hybrid of C. fargesi and C. fargesii were higher than those of C. fargesii and C. bungei and those of C. fargesii and C. fargesii, which were 12.96%, 22.39%, 51.29% and 46.19%. The correlation analysis shows that photosynthetic capacity, chlorophyll content, leaf area and specific leaf weight of hybrid progenies of different hybrid combinations of C. fargesiiwere significant positive correlation. Among 29 cross combinations, the photosynthetic parameters, leaf area and specific leaf weight of female parent selected by Dongshuihuangzhuang and Shijiazhuang were higher than those of Liaojiazhuang and Gaojiazhuang. The leaf area and the maximum net photosynthetic rate of hybrid progenies of Dongshuihuangzhuang 3# × Gaimao 4# were the highest. Preliminary selection of 5 hybrid progeny with heterosis, the gains of leaf area, leaf weight and photosynthetic capacity of 5 hybrid progenies with hybrid advantages were 14.91%, 5.71% and 23.8% respectively.