Triploid Clones Research Articles

Megasporogenesis and female fertility in three edible triploid bananas

The female cytology of three edible triploid banana clones (‘Mysore’, ‘Pisang awak’, ‘Bluggoe’) is described. Irregularities of meiosis and embryo-sac formation are numerous and development is often delayed in respect to ovary development or altogether arrested. Mature embryo-sacs are therefore rare. Comparison of seed fertilities of the three clones with their cytology suggests that embryo-sac formation is limiting to fertility in at least two of them. In ‘Gros Michel’, by contrast, embryo sac frequency far exceeds fertility, thus giving some encouragement to the banana breeder’s hope of manipulating the seed yield of this clone. The observations, for technical and statistical reasons, give little information about the origin of polyploid progeny; indirect inference suggests that both “Rosenberg” and “Musa-type” restitutions are concerned.

Studies on mint breeding : X. Induced triploid clor of Japanese mint (Mentha arvensis L. var. piperascens MAL.).

This investigation was undertaken to see the morphological, physiological and cytological characters of triploid clone of the Japanese mint and also to study its economic values. In 1905 and 1956, 35 triploid clones (3n, somatic number=144:) of the Japanese mint were raised by the crossings of induced tetraploid clones (4n=192) with diploid clones (2n=96). The inverse crossings, however, did not succeed because of the failure of germination of the seeds obtained by crossings. Hence the triploid clone has not yet been obtained by 2nx4n. As the basic number of chromosomes in the genus lklelctho is twelve, strictly mosomes in the genus lklelctho is twelve, strictly speaking the Japanese mint, its triploid and tetraploid clone, should be called octaploid, dodekaploid and hexadekaploid clone, respecfively. However, for convenience' sake, the authors will name them respectively, diploid, triploid and tetraploid clone of the Japanese mint as mentioned above, in this paper. The triploid plants grow well and are somewhat larger than 2n plants in the vegetativc orgnns. Leaves are ovatc-oblong, not so broad as the ovate leaves of 4n plants, but broader than the lanceolate leaves of 2n plants. Guard cells of stomata, hairs and essential oil glands of 3n plants, which are all observed on the epidermis of their leaves, become larger or longer than those of 2n plants, but are not so large or long as those of 4n plants. On the contrary, their numbers in the unit area of leaves are reduced as compared with those in 2n plants, though not so much reduced as those in 4n plants. Flowers come into bloom from July to September in Okayama district. Early clones are as early as 2n ones and late clones are as late as 4n ones. Anthers become atrophied and no fertile pollen is found in the pollensac in any of 3n clones. Seeds set ncither in open pollination nor in back cross to parents. In 1957 about 1800 flowers were tested and only three seeds were obtained. It is presumable that fertility is nearly zero in the female gametic organ as in the male gametic one.

Isolation of triploid Saccharomyces cerevisiae.

THE production of tetraploids in a brewery yeast has been reported by Subramaniam and Krishna Murthy1 and Mitra and Subramaniam2, following treatment with acenaphthene and chrysene. These authors did not present genetic evidence to support their claim, which was based mainly on colony and other gross observations. Cytological evidence has recently been presented for a tetraploid with four chromosomes, derived from a “diploid two chromosome… strain”3. Tobias4 studied a yeast isolated after acenaphthene treatment in terms of survival after X-irradiation, and concluded that the isolate was tetraploid. DeLong and Lindegren5 have characterized certain strains of Saccharomyces cerevisiae as triploid and tetraploid, based on the shapes of survival curves after ultra-violet irradiation. A paper by Lindegren and Lindegren6 has recently appeared, describing the production of tetraploid yeast by crosses of diploids homozygous for complementary mating types. We wish to give a preliminary report on a procedure for the isolation of pure triploid clones of S. cerevisiae.