Research was conducted at the Agricultural Experiment Station—Khan Krum, Northeast Bulgaria during the period of 2014–2017. The aim of the study is to investigate the suitability of selected hybrids No.20-181 and No.20-192, obtained by interspecific crossing ‘Polevka’ (Prunus cerasus L.) × ‘Compact Van’ (Prunus avium L.) as clonal rootstocks for sour cherries. The rootstocks were grafted in a nursery with the cultivars ‘M-15’, ‘Nefris’, ‘Fanal’ and ‘Schattenmorelle’. Prunus mahaleb seedlings were used as the standard for comparison. Characteristics determining growth, the quality of the planting material and the compatibility of the rootstocks with commercial cultivars were tested. The average grafting success rate reported in the spring of the analyzed cultivar–rootstock combinations varied as follows: P. mahaleb (83–90%), hybrid No.20-192 (87–91%) and hybrid No.20-181 (82–85%). The selected hybrid 20-192 (‘Argo 2’) rootstock produces relatively weaker growth than the mahaleb. Hybrid 20-181 (‘Argo 1’) is characterized by the weakest growth. Both tested rootstock hybrids produce planting material with standard trunk diameter and tree height. With the weak growth that rootstock 20-181 induces in the grafted cultivar and the drought tolerance observed in 20-192, it is appropriate to continue the study in an orchard.

The study of the disease Black rot of grapes was carried out in the village of Galabets, Pomorie municipality. The study was carried out in the period of 2022 - 2023. The vine varieties that were monitored were Dimyat, Pamid, Misquet red, Chardonnay, Misquet Ottonel, Naslada, June Blanc and Cabernet Sauvignon. In the village of Galabets, the Misquet Ottonel variety is 2.5/1.4 m apart and the other varieties at distances of 3.2/1.4 m. The vines are grafted onto Berlandieri x Riparia SO4 rootstock. The preplanting preparation of the area includes stock fertilization with 40 kg of P2O5, 50 kg of K2O (active substance) and 3 t of stable manure per decare, harrowing, discing and leveling. The vines are planted in pits of 60/60/70 cm. According to McKinney's classification (1923), slightly sensitive /class 1/ are June Blanc and Naslada (0.1-25%), moderately sensitive is the variety Pamid (25-50%). Misquet Otonel, Misquet Red, in fourth variant compared to the other variants and the lowest, are sensitive. This is due to the application of green pruning operations combined with the use of chemical preparations with a proven effect against black rot.

The study was conducted during the period 2017 – 2018 at the Agricultural Experimental Station – Khan Krum, Shumen region. The experimental orchard was established in the spring of 2011. The following nectarine cultivars were studied: Fantasia, Golden Grand, Morsiani 51, Cassiopeia and Fairlane grafted on a seedling rootstock (Elberta) and clonal GF 677, as well as the frost – resistant dessert-type cultivar Redhaven. In the period 2017 – 2018, negative temperatures were reported, at the end of March and at the beginning of April (-3.6°C and -5.0 °C respectively)which coincided with the full blooming phenological phase; as a result of which the blossoms froze (76 – 100%). A relatively low percentage of frozen blossoms was observed in cultivars grafted on rootstock GF 677. In 2017, the blossom damage was relatively low and yields were obtained, unlike in 2018. Negative spring temperatures had a negative impact on productivity if blossom damage percentage exceeded 80%.