南方松大多数遗传改良计划所采用的良种均产自用优树接穗建立的无性系种子园。过去人们注意力多放在优树的选择和采穗技术上,但是到目前为止已对砧木的类型有所考虑。一个多世纪以来,砧木和间砧的选抒已成为促使嫁接树体矮化和提前结实的措施 Most of the genetic improvement programs used by Southern Pine are produced from clonal seed orchards established with the elite scion. In the past, attention was paid more on the selection and cutting techniques of elite trees, but the types of rootstocks have so far been considered. For more than a century, the selection of rootstocks and anvils has become a measure to dwarf and advance the grafted trees