| Control plant material Control plants of the initial varieties of winter wheat, sown in spring without vernalization of seeds, differed by their vernalization stage. In August and September there was observed in short-staged varieties (Bezostaya 1) heading of a small rate of plants. In 1969, 7.9% of headed plants were observed in the control ; small part of them gave half-mature seeds. When sown for the second time in spring (the first generation), 87.5% of spring-habited plants were obtained. In the second generation the rate of spring-habited plants decreased to 23.1, in the third and forth generations it equaled 82% and 83.9% respectively. In another treatment of the experiment the headed plants in the control of Bezostaya 1 variety equaled 1.1%, in the first generation 34.4%, and in the third generation all of them restored their winter habit. Thus, the control plants of short-staged varieties behave similarly to the experimental plants ; according to natural conditions of complete vernalization they can give spring offspring or restore their winter habit. In long-staged varieties we have another situation. For instance in the control plants of Mironovskaya 808 there headed in 1969 by the 15th of September only one plant, in 1970 on the 30th September - only one plant, in 1971 two plants shooted, in 1972 one plant shooted, in 1973 no shooting and no heading was observed. The number of plants in the control in all years equaled 7253. Similar data are also obtained in other long-staded varieties (PPG-186, IGEN-3). If under Moscow district conditions transformation of the character "winter habit" into "spring habit" can occur when Bezostaya I plants are sown in spring (without preliminary vernalization), the desirable result in the varieties Mironovskaya 808, PPG-186 and IGEN-3 can be obtained only by partial vernalization. The importance of transformation method for plant breeding The change of winter habit is not an independent process ; this change involves the change of other biological and morphological properties and characters and in particular the length and strength of the stem, resistance to lodging, the form and length of the ear, grain quality, etc. Similar results have been obtained by twice performed partial vernalization of the variety Mironovskaya 808 in 1968 and 1970. In both cases spring forms were obtained in the third generation. The diversity of plants in the fifth generation has been studied (Table 5). The treatment of 35 days of vernalization comprised 26 families which differed by the studied characters. There were also short-stemmed families among them (26.9%). Approximately one half of the plants had the stem of medium thickness, which usually ensures better resistance to lodging. There were observed differences in ear length (7-11 sm.), 1000 kernel weight (30-40 g.), grain characters (61% of the lines had vitreous grain) and even in maturing (one family was late-maturing). Similar variability was also observed in the other treatments (50 and 55 days of vernalization). |
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