S.M. Rozov, F.L. Gorel, O.E. Kosterin, V.A. Berdnikov.

Institute of Cytology and Genetics, Novosibirsk, 630090, RUSSIA

A new mutant SGE-0666 was isolated from the M2 progeny of EMS-treated line SG. This mutant is caracterized with a complex of flower and inflorescence abnormalities. (Fig. 1) Although this complex affects almost every parts of flowering structures, not all flowers on one plant are modified to the same dergee and in the same manner, even sometimes it produces nearly normal flowers.

The flowers of SGE-0666 mutant are visibly open from the very early stage of a young bud developing . The small buds commonly look like a star structures of a widely spread sepals, with the anthers and pistil well visible in the center, these buds usually lack petals. Even well developed flowers of the normal size very often are petalless at all, but in such cases some of the sepals develope into petaloid structures, very similar to normal petals. Very often these flowers form two symmetrically positioned sails in the upper part of a flower, developed from two upper sepals. Therefore SGE-0666 mutant gene was called biv - bivexillum. The number of stamens in a mutant plant is sometimes reduced to 5-7, in some cases the flowers contain structures intermediate between the petals and stamens. The pistil and ovary are probably the only flower structures not affected by biv mutation. If the pollen appear to get to the pistil, the ovaries produce normal seeds. Althougth the number of stamens is sometimes reduced, the latter contain normal pollen grains.

The inflorescence of the SGE-0666 mutant line is often two-three times longer than those of the ancestor SG line. Sometimes the inflorescence of biv plants contains large bract-like structures of very varying shape intermediate between bracts and stipulae. Very often the apical meristem shoot of biv plants produces very long inflorescence-like structure. Sometimes it consists of several nodes, marked with bractum-stipula-type rings, but without leafs, and with a single flower on the top. In such cases a plant looks like one with determinant type of stem - the stem stops its growth due to transformation of apical meristem into generative organs, and the further growth of the plant continues by means of primordial buds of the lower nods.

We may suggest the gene biv to be the homeotic gene, as it controls transformation of one plant organs to another: stem structures are transfomed to inflorescence, and one flower parts germs are developed into another flower structures.

Line SGE-0666 was crossed with WL-1238 and WL-1514 tester lines, and the obtained data revealed a significant linkage of the biv gene with d (Table 1.). Unfortunately, there were no other markers of d-segment involved in this cross, so it was not possible to establish a proper position of biv on the linkage map.

This work was partially supported by the Russian State Program for Fundamental Research.