Abstract: In the present study a three-generation Populus deltoides (R)×P.cathayana (S) hybrid poplar pedigree,comprising F₁ and F₂ progenies,was used to investigate the genetic control of resistance to Alternaria alternata (Ala).The susceptibility of parents,F₁ and F₂ to Ala was tested in both the greenhouse and the field.The results suggested that the resistance be determined by a single recessive gene for P.deltoides. To identify the markers linked to Ala resistance,using RAPD markers,in combination with bulked segregant analysis,we analyzed approximately 4200 selectively amplified DNA fragments using 400 primers and identified two markers linked to this resistance gene. Ala is mapped on group 3,and 3.60 cM from RPH12-6 or RPH12-4.The results are the basis for molecular marker assisted selection and early identification of disease resistance varieties.

Key words: Alternaria alternata, Molecular marker, Resistant gene, Poplar