Studies on the breeding of Pelargauium species used for the essential oil production. IV. Interspecific hybrids between tetraploid Pelargonium roseum and tetraploid P. denticulatum.

Both Pelarganium roseum WILLD. and P. denticulatune JACQ, are priginally sterile, but their artificially induced tetraploids can produce fertile pollen and bear good seeds (Tamai et al., 1958, 1963). One hundred and sixty-four flowers of tetraploid P. roseum were pollinated with pollen from tetraploid P. deleticulatum, and 31 mature seeds were obtained (Tab. 1). 19 seeds were sown and two interspecific hybrids were raised (Tab. 2). In this paper, various plant characteristics were compared between the hybrids, and the parental tetraploid species. (In the following paragraphs, “tetraploid P. roseum” and “tetraploid P. delticulatum” are referred briefly as “P. roseum” and “P. denticulatum”, respectively. ) The original somatic chromosome number of diploid P. deleticulatum is 88 and of diploid P. roseum 77, thus their induced tetraploids being about 176 and 154, respectively. The somatic number of the hybrid determined was about 165 (Fig. 1).