Genetic Linkage Mapping in F2 Population of Populus deltoides×P. cathayana by Using AFLP and SSR Marker Detection of QTLs for Growth and Phenology Traits of Poplar Using RAPD Markers Research on the Variation of Populus deltoides×P. cathayana F2 Generation against Alternaria alternata STUDIES ON TRANSFORMATION OF MTLD/GUTD DIVALENT GENES TO POPULUS DELTOIDS×P. CATHAYANA QTLs Mapping for Wood Properties of Populus deltoides×P. cathayana