Genetic transformation and "graft-hybridization" in flowering plants.

Recent pollination experiments with highly irradiated (100,000 r) pollen in Nicotiana have shown that radiation-"pulverized" pollen chromatin can cause genetic transformation of the egg. A new model is proposed here for integration of chromatin fragments into host chromosomes. It is also proposed that heterochromatin may be involved in the process of gene transfer, and in the phenomena of meiotic drive associated with gene transfer.It is suggested that this discovery throws new light on the phenomenon of "graft-hybridization". In spite of many reports to the contrary, "graft-hybrids" have so far been explained only on the basis of their being chimaeras. A mechanism is suggested here by which they may result from genetic transformation.