Rootstock selection from Skierniewice, Poland. Received from Poland by USDA Plant Introduction Station on August 11, 1966. Scions presented by the Research Institute of Pomology, Skierniewice. - USDA Plant Inventory No. 174 'Three promising quince rootstocks for the dwarfing of pear. These stocks are both hardier and more leaf spot resistant than the popular Quince A. This work was started in the early 1930's in Poland when the need for hardier pear rootstocks was first appreciated. Orchards and nursery stoolbeds possessing quince shoots or rootstocks surviving the test winters of 1928-29, '34-'35, '36-37, '39-40, and '41-'42 were examined for exceptional individuals. Three stocks, known as S-1, S-2 and S-3 remained after 25 years of testing and are available for commercial use. All three clones are more resistant to the leaf diseases that will seriously defoliage EM-A. The cold resistance character is indicated by 25 years of observation, in which there was not a single case of damage to roots that had been covered with soil:
S-1 is considered as the most valuable clone, and was selected from a single tree that had been grafted with a pear which subsequently had died. It is very similar to Quince A, but is a more prolific bearer in the stoolbed. It also retains its foliage better, and will unite well with Bartlett.
S-2 was found in East Poland, now Russia, in a nursery stoolbed after the test winter of 1934-35, but does not produce as many shoots in the bed. S-2 plants are quite uniform and seem to be compatible with the varieties of pear that are compatible with Quince A and C.
S-3 developed from a rootstock that originally had been worked with Bartlett. This selection was made after the test winter of 1939-40 and is considered as the most cold resistant of all three clones. It also gives the smallest number of shoots, and this detracts from its acceptability.'
-- quoted from D.F. Millikan and S.A. Pieniazek. 1967. Fruit Varieties and Horticultural Digest 21(1):2.