Этюды в области гибридизации, иммунитета и трансплантации растений

The heterozygosity of the-rye complicates the selectional work. Although we have obtained F 4 hybrids, we do not consider this work finished and here we shall only emphasize that we have produced hybrids distinguished by (a) perennial life cycle; (bj large ears and high straw. The hybrids of this new rye species, produced for the first time in selectional practice, are endowed with valuable agricultural properties. This new species must, therefore; seriously attract the attention of the selection workers. It is known that F x hybrids from crosses between G. hirsutum and G. barbadense are marked by heterosis, high yielding capacities and high fiber qualities. However, segregation in F 2 is followed by sterility and absence of forms similar to F ,. So for only vegetative reproduction has been applied for preserving plants with F x quali­ ties. It is usualy supposed that chromosome doubling in remote hybrids gives a constant and fertile progeny. W e, therefore, crossed (in a hot-house in Moscow) G. hirsutum, 1306 ( 9 ) with G. barba- rense «Pima» ( $ ) • The F 4 seeds were treated for three days with a 0,02 per cent colchicine solution. Amphidiplqids with 104 chromosomes were produced (2n). A similar amphidiploid had been already obtained by A. Kasparian with other parental forms. We had two well vegetating amphidiploid plants. They were marked by unusually vigorous shoots, cortical stems, thickly pubescent lea­ ves, unusual to the parental forms, large stomata. Buds were nume­ rous, flowering proceeded outwardly normally, but fertilization was absent and all the pistils fell off. A ll the treatments, such as application of microelements, ligature of shoots, placement of plant into a cool hothouse, gave no results. Microsporogenesis could be «captured» in the night hours only. It appeared that both micro- and megasporogenesis were unnormal in the first reduction divi­ sion, gametogenesis did not take place at all., The Trinidad geneticist Scovsted had proved that both G. hir­ sutum and G. barbadense are spontaneous amphidiploids from the natural cross of wild species of cotton-plants from the New and Old Worlds. Recurrent amphidiploidy (as in our experiment) caused a regression. Besides, the cells of the plants were overfilled with chromosomes (104 instead of 52). The negative practical result does not, however, diminish its theoretical importance. It is possible to affirm that amphitetraploids w ill always be sterile. * Thus, in this case chromosome doubling in the remote F r hybrid had a pronounced negative effect on fertility; causing complete sterility. Amphidiploidy evidently, causes fertility only in those cases when the amphihaploids are sterile and, vice versa, when the amphihaploids are fertile, the amphidiploids are sterile. Practi­ cally speaking, they are already amphitetraploids. Электронная Научная Сельскохозяйственная Библиотека