Eight cross combinations of Zinnia elegans were made using two recessive nuclear male sterile lines crossed with four restorers using the North Carolina Design II statistical method. Heterosis, combining ability and heritability was analysed using 12 horticultural traits and these demonstrated the advantage of heterosis in hybrid breeding of Zinnia elegans. Heterosis served to increase the number of whorls of ray florets across capitulum and the number of branches, and also decreased plant height, crown size, pedicel length and length of node. Thus, six horticultural traits were improved over mid parent and best parent status to fulfill major breeding goals of this herbaceous flower. The traits of plant height, number of whorls of ray florets across capitulum and pedicel length were primarily controlled by paternal additive effects, whereas crown size was mainly controlled by non-additive effects. Number of branches and length of node were affected both by paternal additive effects and non-additive effects. The ratio of general combining ability to specific combining ability indicated the importance of additive genes in the expression of these traits. Among the parental lines, AH003A and restorer A3 were chosen as primary female and male combiners, respectively. AH001A and restorer S5 were chosen as secondary combiners. The cross AH003A 9 A3 was determined as the most promising combination for producing potted plant characteristics, and AH001A 9 S5 was the best hybrid obtained in this study for cut flower traits. The analysis of combining ability for the parental lines showed that there was no causal relationship between general combining ability and specific combining ability effects.

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To provide theoretical basis for artificial pollination in Lagerstroemia indica L., pollen viability and stigma receptivity were tested and the morphological change of stigma was observed. Pollen viability tested by in vitro culture, stigma receptivity examined by benzidine-H 2 O 2 testing and fruit set estimated by field artificial pollination were analyzed in this study. The maximum pollen viability was observed at 10:00 am one day of anthesis (DA), of which 'Hong Wei' (46.2%) was significantly lower than that of 'Yin Wei' (56.8%) and 'Zi Wei' (62.5%). The stigma receptivity of the three crape myrtle cultivars was sustained for eight days, which was 95.7 to 96.9% at 1 DA to two days after anthesis (DAA), then declined to 75.5 to 79.9% at 3 to 4 DAA and 50.6 to 59.7% at 5 to 6 DAA, and only 29.5% at 7 DAA. Higher stigma receptivity was associated with columnar style, upward stigma, green and wet papillae and copious exudates at stage 1 (1 DA to 2 DAA). Frequencies of fruit set at stage 1 (74.4%) and stage 2 (3 to 4 DAA) (78.9%) were significantly higher than that at stage 3 (5 to 6 DAA) (21.9%). So, selecting pollen at 10:00 am 1 DA and stigma of 1 DA to 4 DAA was a strategy to enhance fruit set in the future artificial hybridizations for crape myrtle.

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