Studies on the breeding of Pelargonium species used for the essential oil production. : II. Artificially induced tetraploid plant in Pelargoleium deleticulatum.

(1) There are several species, varieties or strains of fragrant Pelargon;ium which are utilized fcr the production of commercial geranium oil. In Japan Pelargonium roseulee WILLD. was introduced in 1954 for the purpose of increasing production of the oil and its cultivation is now being spread. Previously the leading species cultivated was Pelargoniulec denticulatum. Both species are commonly sterile and do not bear any fruit owing to the complete absence of their fertile pollen. Judging from a stand-point of Pelargoniulmbreeding, it is, especially desirable that such sterile species be able to produce seeds. With the object of breeding Pelargoleiulee species, we attempted to establish the artificial tetr:aploid strain of P. roseum and succeeded. Moreover, we were able to obtain fertility in this species in company with tetraploidy. In this paper we will report briefly on the pr ocess tf cclchicine treatment and some characteristics of the induced tetraploid. (2) Lateral leaf-buds of a cutting of P. roseum, variety called "Bourbon", which was grown in the propagation house, were treated with water solution of 0.3 % colchicine during a week in January of 1956. At the flowering season in April, there appeared some large fertile flowers upon one of the treated branches, in striking contrast to small sterile Llowers of diploid. The branch bearing large flowers proved to be of tetraploidy by the examination of size of stomata of the leaves. Plants were propagated not only by cuttings of the tetraploid branch, but also by sowing seeds obtained from the large flowers .