| Persistent modifications and their genetic importance
for spring wheat breeding Part II I.E. GLOUSHCHENKO Laboratory of Experimental Biology of Lenin Au-Union Academy of Agricultural Sciences, Leningrad, U.S.S.R. Transformation of the character "winter habit - spring habit" in wheat varieties with different length of the vernalization stage The study of the variability of the character "winter habit" in short-staged (Bezostaya 1) and long-staged (PPG-186, Mironovskaya 808 and IGEN 3) wheat varieties has shown considerable differences. The work on the winter wheat Bezostaya 1 was begun in 1965. The experiments were repeated many times with nearly the same results. The chromosomal apparatus was studied in the spring forms of the fifth generations. All plants had normal chromosome numbers (2n =42). The monosomal analysis of the transformed material was begun in the same generation. There were analysed F1 and F2, obtained from crossing the lines 5A, 2B and 5D of Chinese Spring wheat with the spring whest Bezostaya 1. The analysis confirmed the stability of the transformed spring forms. At present breeding work has been carried out on the transformed tenth generation of the spring wheat Bezostaya 1 and on the seventh generation of the spring wheat Mironovskaya 808. We shall examine at greater length the third generation of the varieties Bezostaya 1, Mironovskaya 808, PPG-186, IGEN-3, partial vernalization of which took place in 1970. This experiment particularly shows the differentiation of the characters of "winter habit" and "spring habit" when compared with the preceeding generations. During all three years experimental plants were grown under individual isolation. Unlike the experiments of the preceeding years the change in the character of Bezostaya 1 has taken place in the treatments having longer periods of vernalization (Table 3). Thus, 35 days of vernalization in the third generation gave 85.3% of spring plants, 40 days of vernalization induced restoration of the character "winter habit", and 45 days of vernalization consolidated the character "spring habit" in all experimental plants. Of special interest is the work on the variety Mironovskaya 808. The data given in Table 4 show that all the plants in the third generation of the 15 days treatment restored winter habit, though the rate of spring forms in the two preceeding generations was rather high. In the treatment of 50 and 55 days of vernalization all the plants were transformed into spring plants. Short periods (three days) of mass and early (from the 20th to the 23d of June) heading in the third generation show that three years suffice to transform the plants of the variety Mironovskaya 808 into spring forms. The plants of the variety PPG-186 behaved differently. The number of spring forms increased in the second generation when compared with the first generation, but in the third generation the plants of 35 and 55 days of vernalization had complete restoration of winter habit. In the treatment of 30 days of vernalization the rate of spring plants decreased to 1.2%. In the treatment of 40 days of vernalization the number of spring plants increased and amounted to 97.4% in the third generation. Three years of spring resowing are not enough for making stable spring habit in the plants of this variety. In a number of experiments we have not succeeded in transforming plants of the most long-staged variety IGEN-3 into spring plants. The plants which headed during previous years restored their winter habit in the second or third generations. The first reassuring results were obtained in the treatments of 40 and 65 days of vernalization which took place in 1970. Early and mass heading of the plants after 40 days of vernalization favoured persistent spring habit in successive generations. The analused material allowed to draw a conclusion that directed transformation of winter forms into spring forms is possible. |