With the purpose of developing dwarfing rootstocks for stone fruits, interspecific hybridizations between Microcerasus and other Pruns species were carried out.
When used as a seed parent, P. japonica had relatively high cross-compatibility with P. persica, P. armeniaca, P. mume and P. salicina, whereas its compatibility with P. besseyi or P. tomentosa was inferior. There was no seed set from the crosses between P. japonica and P. avium.
Considerably high cross-compatibility was found between P. tomentosa and P. besseyi but there were few seeds set between P. tomentosa and other Prunus species.
When P. besseyi or P. persica was used as the seed parent, there was no seed set with any interspecific cross-combination.
Although pollen tube growth in the styles was slower with interspecific crosscombinations than with self-pollination, pollen tubes of the cross-compatible species reached the upper portion of the ovary by 6 to 10 days after pollination.
In contrast, pollen tubes of P. avium stayed on the stigma or in the upper portion of styles of other species during the period examined, and their tips often swelled.The germinability of seeds obtained from the interspecific hybridizations was relatively high, but most of the resultant seedlings died at young stages. The hybrids that still survived after one year were P. japonica×P. persica wild form, P. japonica×P. armeniaca Heiwa, P. japonica×P. salicina Soldam, P. japonica×P. besseyi and P. tomentosa×P. besseyi.
These hybrids evidently showed morphological characteristics resembling their parents and some of them flowered and bore fruits.