Abstract only

Research history of crossing of genetically distant forms is accounting for more than two centuries. I. Kehlreiter was the first to cross and analyze more than 50 varieties of hybrid combi- nations. Presently the study of processes taking place in distant hybridization is intensively continued. Investigation of the mechanism and specific features of this process is carried out from the family to molecular levels (between families, between species, between wild and cultured forms, between tissues, between cells and molecules). The reason of such vital interest in research of distant hybridization is the diversity of results of this process. Namely, the cycle of distant crossing produces absolutely unique individuals, which never before existed in nature. Synthesis of new species is carried out, and researchers gain the opportunity to establish the possible paths and mechanisms of evolution through investigation of the separate stages of this process. Along with theoretical importance, the distant hybridization is of a significant practical application, as crossing of taxonomically distant forms gives the broad range of hybrid mechanisms, which are widely used in breeding. This method ensures successful adoption of beneficial characteristics of wild species by the cultured plants. Regardless of the wide application of distant hybridization nowadays, utilization of its potential is still restricted due to its side problems. Such as, low yield of hybrid forms and their absolute or partial sterility. In order to overcome crossing impotence, ensure increase in yield of hybrid grains as well as solve other problems different methods are applied, such as pistil instigation by stigma, pollination with mixed pollen, treatment of pollen grains with various mutagens, etc. We have studied effect of gamma- radiation on increasing combaining abity of tetraploid and hexaploid varieties of wheat. Hexaploid (T. aestivum, T. spelta, T. macha) and tetraploid (T. durum, T. carthlicum, T. polonicum) varieties were used in our experiment. The grains were irradiated at the rates of 3, 5, 10, 15 and 20 krad. Produced plants were emasculated. Three crossing patterns were applied: radiated maternal plants X non-radiated pollinator, non- radiated maternal plant X radiated pollinator, and finally, radiated maternal plant X radiated pollinator. Analyses have shown that the first and the third patterns do not produce positive results. Namely, emasculation of radiated plant is difficult, as damage or detachment of pistil easily occurs during the separation of pollen with pincers. At the same time, in case of pollination of the flowers with the damaged pistils, seed setting in hybrids frequently matches that of the check or is even lower by 1.3%. Crossing of the pair of radiated parents also failed to produce positive results, whereas all combinations with the non-radiated maternal plant and the pollen of the mate radiated by 5 krad dose were positive. In crossing of hexaploid wheat with tetraploid varieties, seed setting of hybrid grains have increased by 3.7% in comparison with the check, while in interspecific crossing of tetraploid varieties at 5 krad doses seed setting of hybrid grains had increased by 9.4%-12%. Application of 3 krad or 10 krad and higher doses rendered no positive results. Our experiments have ascertained the following general arrangement: at crossing of varieties with the equal number of chromosomes the seed setting percentage of hybrid grains is higher compared to crossing of varieties with the different set of chromosomes.

English

0409|AGRIS 0401|AL-Wheat Program

Juan Carlos Mendieta

CIMMYT Publications Collection