Flowering biology characteristics of different peach cultivars under greenhouse conditions

Peach (Prunus persica) is a popular temperate fruit now cultivated worldwide. China ranks first in the world both in peach planted area and production. In the last 10 years, peach cultivation has developed quickly and spread to most of northern China. The problem is that the flowering biology of peach cultivars has been insufficiently studied and poor pollination has often caused low fruit set and yield for peach trees in greenhouses. In order to evaluate the flowering biology of different peach cultivars in greenhouses, the flowering dynamics, anther dehiscence, pollen quantity, pollen viability, and stigma receptivity of four major peach cultivars (Prunus persica "Okubo", P. persica "Zaolupan", P. persica "Ruiguang 5" and P. persica "90342") were investigated in greenhouses in Beijing. In the study, 80 flowers for each cultivar were studied for the timing of different flowering stages, 18 flowers were used to obsever anther dehiscence development, 50 anthers were used to count pollen grains number per anther, 50 flowers were used to count anthers number per flower. A TTC test was used to assess pollen viability, and a benzidine-hydrogen peroxide test was used to assess stigma receptivity. The results showed that the start time of blooming varied by 8 days among cultivars, which were ranked (from earliest to latest) - "Ruiguang 5", "Zaolupan", "Okubo", "90342". Cultivar "90342" had a two-day full-bloom stage for single flower, which was significantly shorter than other three cultivars. The full-bloom stage of the other three cultivars lasted for 4 5 days. The starting time, duration, and peak period of anther dehiscence varied among the four cultivars. Significant variation in pollen quantity was also observed. Cultivar "90342" had the largest number of pollen grains per flower (100 360 ± 8 017), followed by "Okubo" (91 485 ± 8 002), "Ruiguang 5" (73 245 ± 5 034) and "Zaolupan" (59 609 ± 5 048). The highest pollen viability was found on the day when the flower opened fully in "Okubo", "Ruiguang 5", and "90342", which were 44.8% ± 3.1%, 52.4% ± 4.2% and 32.8% ± 4.5% respectively. The pollen of "Zaolupan" had the highest viability 63.3% ± 3.7% one day after the flower opened fully. Pollen viability lasted only three days in "Ruiguang 5" and "90342", while "Okubo" and "Zaolupan" had a greater longevity of 6 7 days. The receptive period of the stigma remained for 6 7 days, with the strongest receptivity 3 4 days after the flower opened fully in "Okubo", "Zaolupan" and "Ruiguang 5". However, the receptive period of cultivar "90342" lasted for just 3 days, with the greatest receptivity 2 days after the flower opened fully. This study contributed new information not only for differences in pollination biology among the four cultivars and for the scientific management of greenhouse peaches, but also for the broader study of pollination mechanisms.