Morphological characteristics and germination of pollen in European and Japanese plum cultivars

In six cultivars of European plum (Prunus domestica L.) and six cultivars of Japanese plum (Prunus salicina Lindl.), pollen morphological characteristics: length (L), width (W), length to width (L/W) ratio, and percentage of pollen grains of normal size and shape, small size, and irregular shape were examined using scanning electron microscopy. In addition, pollen germination in vitro was studied using the agar plate method in a medium containing 15% sucrose. It was found that European plum cultivars have larger pollen grains (53.4 μm in length and 28.3 μm in width on average) compared to Japanese plum cultivars (length and width of 41.0 μm and 22.9 μm, respectively). Besides, European plum cultivars had more elongated pollen grains (L/W ratio of 1.88) compared to Japanese plum cultivars (L/W ratio of 1.79). The percentage of pollen grains of normal size and shape was higher in European plum cultivars (69.3%), compared to Japanese plums (51.9%). Similarly, pollen germination in vitro was significantly higher in European plum cultivars (66.2%) compared to Japanese plums (35.6%). A significant correlation was established between the percentage of pollen grains of normal size and shape and pollen germination in vitro (Pearson's correlation coefficients of 0.896 and 0.822 for European and Japanese plums, respectively)