PLUM SELECTION IN THE CENTRAL ZONE OF THE U.S.S.R.
Industrial plum cultivation developed especially in the south of the U.S.S.R., in Ukrain, Georgia, Armenia, in the south of the R.S.F.S.R.
In the central zone, where selection works developed more extensively only during the last 35 years, plums were little cultivated up to now, due to the lack of high quality, frost resistant varieties. In the south of the U.S.S.R., the varieties grown belong mostly to the P.domestica L. variety: Rosioara varatica, Record, Vinete obisnuite, d'Agen, Reine Claude verte, Anna Späth, Reine Claude d'Althan etc.
In the central zone, the following varieties of P.domestica L. are grown: Précoce rouge, Record, Reine Claude kolkozienne etc.; the varieties of P.spinosa L. are: blackthorn, macrocarpa, tsaregradski blackthorn, characterized by their resistance to frost, and low fruit crops of poor quality.
Other plum varieties such as: P.americana Marsh, P.salicina Lindl., P.ussuriensis Kov. and Kost., P.nigra Alt., P.cerasifera Ehrh., are little spread.
Low temperatures, prevailing in the central zone, and which reach during certain years -40°C, are detrimental to plums; the tree wood is usually damaged. This brings about