Studies on the ISSR Marker Analyses of the Columnar Gene in Apple Differential Expression Analysis of cDNA Between Columnar and Non-columnar Apples Using cDNA-AFLP Studies on the ISSR Marker Analyses of the Columnar Gene in Apple Differential Expression Analysis of cDNA Between Columnar and Non-columnar Apples Using cDNA-AFLP Comparison of Leaf Structure and Chloroplast Ultrastructure BetweenColumnar and Standard Apples