Vulnerability of sweet cherry cultivars to continuous periods of spring frosts in Plovdiv, Bulgaria

S. Malchev, S. Savchovska*

Fruit Growing Institute – Plovdiv, 12 Ostromila Str., 4004 Plovdiv, Bulgaria

(Manuscript received 31 August 2020; accepted for publication 16 October 2020)

Abstract. The periods with continuous freezing air temperatures reported during the spring of 2020 (13 incidents) affected a wide range of local and introduced sweet cherry cultivars in the region of Plovdiv. They vary from -0.6°C on March 02 to -4.9°C on March 16-17. The duration of influence of the lowest temperatures is 6 and 12 hours between March 16 and 17. The inspection of fruit buds and flowers was conducted twice (on March 26 and April 08) at different phenological stages after continuous waves of cold weather conditions alternated with high temperatures. During the phenological phase ‘bud burst’ (tight cluster or BBCH 55) some of the flowers in the buds did not develop further making the damage hardly detectable. The most damaged are hybrid El.28-21 (95.00%), ‘Van’ (91.89%) and ‘Bing’ (89.41%) and from the next group ‘Lapins’ (85.98%) and ‘Rosita’ (83.33%). A larger intermediate group form ‘Kossara’ (81.67%), ‘Rozalina’ (76.00%), ‘Sunburst’ (75.00%), ‘Bigarreau Burlat’ (69.11%) and ‘Kuklenska belitza’ (66.67%). Candidate-cultivar El.17-90 ‘Asparuh’ has the lowest frost damage values of 55.00% and El.17-37 ‘Tzvetina’ with damage of 50.60%.

Effect of the length of the interstock on the growth and reproductive aspects of sweet cherry cultivar Biggareau Burlat

P. Kaymakanov*

Department of Fruit Growing, Faculty of Viticulture and Horticulture, Agricultural University Plovdiv, 12 Mendeleev, 4000 Plovdiv, Bulgaria

Abstract. In the period 2012 – 2013 the influence of 3 interstocks on growth and fruit bearing of the sweet cherry cultivar Biggareau Burlat grafted on Prunus mahaleb L. – P1 seedling rootstock was tested. As interstocks were used Gisela 5, the sour cherry cultivar North Star and the Hybrid 2/10, each of them with length 10 and 30 cm. The trees were planted in March 2006 with planting distance 6.0 x 4.5 m and were grown without irrigation and training. The sweet cherry cultivar Stella which was planted in adjacent rows was used for pollination of Biggareau Burlat. It was established that under the influence of the longer intesrock the trunk size was reduced in the area of the rootstock and the interstock itself. The trunk size was bigger in the area of the scion. The differences were more pronounced where Gisela 5 was used. The longer interstock induced weaker growth of the trees grafted on Gisela 5 and reduced the crown volume. The trees with the longer interstock have larger number of blossoms per linear metre of two-year-old wood, but with lower percent of fruit set. Despite the lower fruit set the trees with the longer interstock have higher cumulative yield compared to the crown volume and the differences to Gisela 5 are proved.

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Studies on some cherry clonal rootstocks in nursery

G. Dobrevska
Abstract. The vegetative manifestations of three cherry clonal rootstocks Merisier F12.1, Saint Lucie GF 64 and Gi-Sel-A 5, grafted with the variety Summit, were studied in nursery. Merisier F12.1 and especially Gi-Sel-A 5 have earlier attenuation in the pace of the rootstocks thickening in the nursery during the I-st year. Under the influence of slowly growing Gi-Sel-A 5 the graft has a lower rate of weight gain and increase in height. Summit/Saint Lucie GF 64 has the greatest length of annual growth.

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