| Persistent modifications and their genetic importance
for spring wheat breeding Part III I.E. GLOUSHCHENKO Laboratory of Experimental Biology of Lenin All-Union Academy of Agricultural sciences Persistent modifications obtained during the transformation of winter habit into spring habit In our work modificational variability preceeded hereditary consolidation of the studied character. As it had already been said, transformation depended on the number of days of seed vernalization, on the state of plants, and the conditions of the year, both during seed vernalization and during growing the first and the second generations. It is precisely this that accounts for considerable differences in plant behavior during vernalization in different years, their change towards spring habit or their restoration of winter habit. Thus, in the first generation of the variety Bezostaya 1 out of 415 sown families of the treatments 35, 40 and 45 days of vernalization 85.9% families (98.4% of plants) remained winter-habited. In the second generation 20 families were sown and all of them turned out to be semispring-habited. Out of 161 plants in the experiment 54.8% restored their winter type of development. In the third generation 16 families were sown and 56.3% of them were winter-habited. Out of 273 plants 11.7% turned out to be winter-habited. In the first generation of the variety Mironovskaya 808 out of 211 families of all treatments 95.7% families (98.2% out of 2064 plants) remained winter-habited. The second generation was represented by 11 families ; one family become completely winter-habited (45 plants out of 149 plants or 30.3%). In the third generation, comprising 33 families, 6 families or 18.8% were winter-habited. Out of 760 plants 87 (11.5%) turned out to be winter-habited (on account of the treatment of 15 days of vernalization in which all plants reversed towards winter-habit). In the first generation of the variety PPG-186, 253 families were sown ; out of them 94.6% of families (98% of plants) remained winter-habited. In the second generation one family out of 21 retained its winter habit. Out of 140 plants 33.2% restored their winter habit. In the third generation out of 67 families 26.9% of families (19.3% of plants) were winter-habited. Modificational variability is expressed specifically by different varieties in different years. Thus,if in the variety IGEN-3 it ends more often in the second generation and in Mironovskaya 808 in this generation there takes place a strongly pronounced differentiation into winter and spring forms, in Bezostaya 1 it is observed up to the fifth generation. Thus, in the experiment with partial vernalization, begun in 1965, the rate of spring plants of the variety Bezostaya 1 increased from the first to the fifth generations and equaled 16.3, 27.0, 43.4, 98.5. and 100% respectively. In the similar experiment, repeated in 1968, in the fifth generation 61.3% out of 6121 studied plants were spring-habited, and 38.7% of plants reversed to winter habit. It follows from the above mentioned that transformation of persistent modifications into genotypical changes is accomplished in some varieties in the early generations and in the others in fairly late generations. |
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