A haploid plant inToria (Brassica Campestris L.)

Summary

A spontaneously occurring haploid plant in one of the open-pollinated cultures oftoria is described for the first time.

The haploid was a reduced replica of the diploid plant with smaller leaves and flowers. It flowered at the same time as the diploid and after setting a good amount of seed under conditions of open-pollination died with the rest of its sister plants.

The somatic chromosome number of the haploid was determined in meristematic cells of young leaves as 10 and that of the diploid as 20. A few cells with the diploid number of chromosomes were found scattered in the leaf tissue of the haploid.

At meiosis, the haploid showed 10 univalents from diakinesis to anaphase I in each pollen mother cell, Occasionally, however, a loosely paired bivalent was noticed in some cells. At division I the univalents either segregated at random into two groups or collected to form an interphase nucleus. Division II in the former case produced tetrads of unequal spores, and in the latter dyads of equal spores.

A few pollen mother cells with the diploid number of chromosomes were also noticed in the haploid ; these were seen to undergo normal meiosis producing tetrads with equal spores.

As a result of dyad formation in a large number of haploid pollen mother cells and tetrad formation in the few diploid pollen mother cells, the pollen fertility of the haploid was found to be as high as about 60 per cent. Seed-setting in the haploid was also fairly high under conditions of open and cross-pollination. The possible utilisation of haploidy in practical breeding is discussed.