| Ble Tom Pouce Blanc (T. aestivum L.), a source
of genes of solid stem* S. TSVETKOV The Institute for Wheat and Sanflower General Toshevo, Bulgaria For the period 1963-1972, an interspecific hybridization was carried out at the Institute with the aim of transferring stem solidity of T. durum DESF. on to T. aestivum L. In spite of the newly developed forms of common winter wheat with solid stem and resistant to Cephus pygmaeus L. (TSVETKOV, 1971), researches entailed great difficulties and time consumption. Our inferences turned analogous to those of YAMASHITA (1937), PLATT and LARSON (1944) MCNEAL (1956, 1961), LARSON (1959, 1959a), LARSON and MCDONALD (1963), WALLACE and MCNEAL (1966) and MCKENZIE (1965). We thus were bound, in our later studies, to seek out another solving of the problem, namely, developing such common winter wheat varieties which to possess dominant and semidominant genes for solid stem, and be, afterwards, utilized for the selection of new productive forms of common winter wheat with solid stem and resistant to Cephus pygmaeus L. By analysing stems of a number of common winter wheat varieties in 1970, we came across an interesting fact that individual plants of Ble Tom Pouce Blanc characterize for their various degree of stem solidity in the internodes. As a result of selection, a line was developed out of Ble Tom Pouce Blanc, with highly solid stem in the internodes. In fact there are reports about Ble Tom Pouce Blanc (JACUBCINER, 1959; ZEVEN, 1969; RUDENCO and UDACHIN, 1969), but there are no such about its solid stem as a source of genes for breeding. Stem solidity was determined by three crossesections in the first top (ear-next) internode and by a cross section in the middle of every next (2nd, 3rd, 4th, 5th) internode. The cross sections of the first top internode were made 2.5 cm. below ear, in the middle of the internode and 2.5 cm. above the base. Degree of stem solidity was determined by the scale of SAPEGIN (1938) and LARSON (1959). For conveniencies, recordings were accomplished consecutively from top to bottom of every internode (five in the whole). Data given in Table 1 show, that in the cross section of the first top internode 2.5 cm. below ear, the newly selected line of Ble Tom Pouce Blanc coincides by the degree of stem arrangement with the hollow stem of the standard Bezostaya 1 common wheat variety as well as the hard No. 1522 wheat (T. durum DESF.) with a hollow stem. However, the two lower cross sections show, that stem solidity of Ble Tom Pouce Blanc in the first top internode sharply increases from the middle of the internode thus reaching a degree of 4.6 which, according to the scale at use, proves almost solid with only a tiny opening. Stem solidity in the next four internodes (from top to bottom) also preserves the same (Fig. 1) with insignificant variations mainly in the second and third internodes; while Bezostaya 1 winter wheat variety and the hard No. 1522 wheat possess fully hollow internodes. With the aim of transferring stem solidity of the newly selected line of Ble Tom Pouce Blanc to the progenies we made, in 1970, some reciprocal crosses between the solid-stem line of Ble Tom Pouce Blanc and the hard hollow-stem wheat No. 1522 (T. durum DESF.). From the cross sections it was established that stem solidity of the aforesaid line of Ble Tom Pouce Blanc transfers to F1 hybrids as a dominant character. Hybrid plants characterize for the nearly solid stem, identical to that of Ble Tom Pouce Blanc (Table 1). We believe that data obtained are a contribution to the genetics of this wheat variety, which apart from its possessing genes of dwarfness (ZEVEN, 1969) appears also as a source of genes of solid stem. At present we are in possession of F2 dwarf forms of common winter wheat with solid stem. Analyses of F2 hybrid with respect to the factors causing stem solidity in Ble Tom Pouce Blanc are now in progress. Crosses were carried out between Ble Tom Pouce Blanc and other common wheats with the aim of finding out differences in the manner of inheritance of stem solidity in the intervarietal hybrids. Namely, some crosses were made between Ble Tom Pouce Blanc and the Bulgarian common winter wheat variety, named "Dobrich", which is known for its hollow stem and high resistance to diseases (No. 11-32-1140). |
| *A newly selected line of Ble Tom Pouce Blanc with solid stem in the internodes. |