backcrossed is backcross's Past Participle

backcross

US 
UK 
  • n.〔遗〕回交杂种;〔遗〕反交
  • v.〔遗〕回交
  • Web逆代杂交;回交作用;倒剪
Plural Form:backcrosses  Present Participle:backcrossing  Past Participle:backcrossed  
n.
1.
〔遗〕回交杂种
2.
〔遗〕反交;回交
v.
1.
〔遗〕回交,逆代杂交