Assessing gene flow in apple using a descendant of Malus sieversii var. sieversii f. niedzwetzkyana as an identifier for pollen dispersalStefanie Reim, Henryk Flachowsky, Maria Michael and Magda-Viola HankeEnviron. Biosafety Res., 5 2 (2006) 89-104DOI: https://doi.org/10.1051/ebr:2006016