Studies indicate that plastid inheritance in two thirds of the sexual hybrids of angiosperms is maternal while in a majority of sexual hybrids of gymnosperms it is paternal. This difference may be because in angiosperms pollen plastids degenerate prior to pllen maturation and fertilization, during fertilization, or in the zygote, while in gymnosperms the female plastids become excluded from the neocytoplasm following fertilization. In tree species, factors such as long generation cycle, lack of plastid mutants, and in most cases delayed fertilization following pollination has limited investigations based on sexual crosses. An alternative is to utilize somatic hybrids and reciprocal cybrids produced via protoplast fusion. In the research planned, the control of plastome transmission patterns(s) in an angiosperm tree will be investigated. More specifically, reciprocal cybrids will be produced, plastome transmission pattern(s) will be identified in elm fusion products, and the possible role of cytoplasmic/nuclear genome interactions in such transmission will be investigated. This is a promising approach to an importent problem in plant biology.
