Some growth and reproductive traits of six plum cultivars

The study was carried out in the experimental plantation of the Fruit-Growing Institute - Plovdiv in 2014 and 2015 with six plum cultivars ‘Bellamira’, ‘Jojo’, ‘Tophit plus’, ‘Topstar plus’, and ‘Topgigant plus’, compared to ‘Stanley’ that was used as a standard. The following traits were studied: angle between the skeletal branches and the central leader, annual shoot length growth, distribution of the different fruiting twigs (spurs and shoots) on fruiting wood of different age, the average number of flower buds on spurs and shoots and distribution of fruits on branches of different age. The largest angle of skeletal branches was found in the cultivars ‘Jojo’ and ‘Bellamira’, 68.1 and 60.6°, respectively. The biggest shoot length was recorded in ‘Bellamira’ and the smallest one in ‘Jojo’, ‘Tophit plus’ and ‘Stanley’. The basic fruit bearing twigs in plum are the spurs, predominantly distributed on two- and three-year-old fruiting wood. The number of flower buds in a spur varied from 2.1 to 2.2 and the average number of flowers in a flower bud was 1.7-2.1. According to the distribution of fruits, the studied plum cultivars can be divided into three groups: cultivars bearing fruits predominantly on young fruiting wood (one-year-old shoots), cultivars bearing fruits predominantly on two- and three-year-old wood and cultivars bearing fruits evenly along the fruiting wood of different age.