Abstract
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-H2O2 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. Key words: Lagerstroemia indica L., dimorphic pollen, pollen viability, stigma receptivity, fruit set.
Highlights
Lagerstroemia indica is a deciduous shrub or small woody species native to China, having been cultivated for 1500 years (Zhang, 1991; Chen, 2001)
Higher stigma receptivity was associated with columnar style, upward stigma, green and wet papillae and copious exudates at stage 1 (1 day of anthesis (DA) to 2 days after anthesis (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%)
Summary
Lagerstroemia indica (commonly known as crape myrtle) is a deciduous shrub or small woody species native to China, having been cultivated for 1500 years (Zhang, 1991; Chen, 2001). Systematic studies on pollen viability and stigma receptivity have been reported in a varity of genera, for example, pollen longevity of Tectona grandis (Tangmitcharoen and Owens, 1997a, b) and Grevillea robusta (Kalinganire et al, 2000) remained for 3 and 4. Integrated study on pollen viability and stigma receptivity in L. indica has not been reported previously. The purpose of the present study was to provide theoretical basis for enhancing fruit set and developing new varieties in L. indica crossbreeding, concentrating on the pollen viability, pollen longevity, timing and duration of stigma receptivity and fruit set under defined dimorphic pollen and stigmatic developmental stages
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