Ovule development at anthesis in Japanese plum (Prunus salicina Lindl.) cultivars

The stage of ovule development at anthesis has been studied in two consecutive years in seven major cultivated plum cultivars: ʹRed Beautʹ, ʹFortuneʹ, ʹAngelenoʹ, ʹSanta Rosaʹ, ʹLarry Annʹ, ʹSon Goldʹand ʹGolden Japanʹ. Ovules exa¬mined were in general delayed. In much of them mature embryo sacs were not found at time of anthesis. Differences among cultivars were found and these differences were consistent during both years, indicating a genetic determina¬tion. In addition, a high heterogeneity of the developmental stage of the ovules examined in each cultivar was obser¬ved. The year influenced the developmental stages of ovules at anthesis, and ovules were more delayed in 2002 than in 2003. Cultivars which showed a more advanced ovule development were those that flowered later, in spite of the fact that chilling requirements for breaking of rest were adequately fulfilled during both years. This work gives inte¬resting information regarding the stage of ovule maturity at anthesis in Japanese plum cultivars, which is closely re¬lated to their fruit set viability.