I. Research Notes

An attempt for transferring stem solidity of T. durum DESF. to T. aestivum L. with the aim of developing new forms of winter common wheat with solid stem, resistant to Cephus pygmaeus L.

Stoyan TSVETKOV

The Institute for Wheat and Sunflower, General Toshev, Bulgaria

Stem solidity present in certain hard wheat varieties, which impart resistance to sawflies of the genus, Cephide to them has made many workers to attempt to transfer stem solidity by hybridization to common wheat (PLATT and LARSON 1944; LARSON 1959; LARSON and MCDONALD 1963; MCNEAL 1961; MCKENZIE 1965; TSVETKOV 1969, l971). However, almost all attempts in this respect evoked great difficulties. YAMASHITA (1937) and later MATSUMURA (1947) established "e" chromosome of D genome as XX chromosome, classified by SEARS in his nomenclature to possess a hollow stem gene, which depresses genes for solid stem in A and B genomes.

For the period 1963-1970 an interspecific hybridization was undertaken at this Institute, with the aim of transferring stem solidity of T. durum DESF. to T. aestivum L.

We resorted, for this hybridization, to No. 13 and No. 233-II hard wheat varieties with solid stem (T. durum DESF.) and to No. 14, No. 11, No. 301 and Bezostaya 1 common wheat varieties with hollow stem (T. aestivum L). Reciprocal crossings were made among the individual varieties of both species. Picking out of the forms of common wheat with stem solidity was accomplished only after the disintegration in F_2. Stem solidity of the hybrid material was determined through the use of the technique of SAPEGIN (1938) and LARSON (1959).

Results given in Table 1 show transferring of stem solidity of T. durum DESF. to T. aestivum L. to be progressed with great difficulty.

In 1966, 1817 hybrid forms of common wheat in F₃ were analysed and only 0.39 per cent of them showed stem solidity in the topmost internode, while 0.17 per cent possessed solid stem in all internodes from top to bottom. In 1967 we had the possibility of fulfilling picking out at a wider range of hybrid combinations. Thus of the 879 hybrid forms analysed, 2.50 per cent showed solid stem only at the topmost internodes, and 0.91 per cent possessed a complete stem solidity.

In our research work more significant results were obtained by the crossing of Bezostaya 1 and No. 11 (hollow stem) x No. 13 hard wheat (solid stem) and No. 233-II (solid stem at the topmost internode only); from these crosses, a considerable number of winter common wheats (T. aestivum L.) with solid stem were developed.

Data in Table 2 refer to the extent of stem solidity, by internodes, of certain newly selected constant forms of winter common wheat. Results obtained show that according to the extent of solidity of the stem in its topmost internode and in those following, the hybrid form of Bezostaya 1 x No. 13 resembles the paternal parental component, No. 13 (T. durum DESF.), with solid stem, and even exceeds it in certain internodes. Of particular interest here are the data obtained with the hybrid lines of common wheat with solid stem, i.e. No. 11 x No. 233-II, and Bezostaya 1 x No. 233-II. While the maternal parental components, No. 11 and Bezostaya 1 (T. aestivum L.), are notable for their hollow stem, and the paternal component, No. 233-II (T. durum DESF.), for its solid stem only in the topmost internode, the winter common wheat - No. 11 x No. 233-II as also Bezostaya 1 x No. 233-II-are notable for their solid stem in all internodes (Table 2, Fig. 1).

The importance of the newly developed winter common wheats with solid stem may best be judged only when solidity is treated on the basis of resistance to Cephus pygmaeus L.

Data in Table 3 show that damage caused by Cephus pygmaeus L. in Bezostaya 1 winter common wheat with hollow stem goes up to 97.8 per cent, while in the newly developed Bezostaya 1 x No. 233-II winter common wheat it runs only to 17.2 per cent.