A biological method for managing the yield of Libya grape variety on a 41B Rootstock

Advances in grapevine biotechnology are associated with manipulation of vegetative and generative plant organs, effective use of the soil and climate potential of agricultural lands, and biological features of grape genotypes. Grapevine biotechnology allows grape productivity to be increased without additional investments. In this work, we studied table grapes of the Libya variety grafted onto a Chasselas.×V. Berlandieri 41B rootstock to determine variations in grape productivity depending on the different load of vines with shoots and bunches. The research was carried out in the Central Agroecological Zone of Viticulture (fourth subzone) of the Krasnodar Krai, in vineyards with drip irrigation and covered viticulture. The vines were planted according to a 3.8×2.0 m scheme with a density of 1316 plants per hectare. The vines were supported with a high-trunk two-arm horizontal cordon system. The average annual air temperature at the experimental site equaled +12.5... 13.0 °С; the sum of active temperatures was 3 900-4 100 °С; the maximum temperature during vegetation reached +40 °С; the minimum temperature of -30 °С was recorded in winters during dormancy. The annual precipitation level comprised 700-800 mm. The soils were low-humus, leached powerful chernozems. In terms of productivity, grapes of the Livia variety respond effectively to canopy management techniques. In this work, changes in bunch weight and grape yield were monitored depending on the load of vines with shoots and bunches. Under the studied agroecological conditions, the largest bunch mass of 870 g was achieved at the lowest load of 20 shoots and 22 bunches per vine. The maximum grape yield of 36.3 t/ha was observed with an average load of 26 shoots per vine and the largest load of 37 bunches per vine. The dependence of yield on shoot number was rather low, r = 0.08; on bunch number was medium, r = 0.53; on bunch mass was high, r = 0.75. The largest share of marketable grape yield of 98% was achieved at the load of 20 shoots and 22 bunches per vine.