Scientific Journal of KubSAU

The value of the initial material for selection for heterosis is primarily defined by the combining ability in respect to the main economically valuable characteristics. Combining ability with respect to “grain productivity” has been studied among fourteen selfpollinated lines of maize of early ripening and three testers in the system of hybrid combinations. We have proved that weather conditions have an influence on the variability of the estimates of the combining ability. We have identified the new self-pollinated lines of maize SP 165 and SP 175, which are characterized by invariably high evaluations in the effects of GCA (gi) in different years. The new self-pollinated line SP 167 has got high variants of SCA (δ2si). The new lines SP 161, SP 163, SP 167 and SP 174 have been characterized by the variability of the evaluations in the effects of GCA. They are related to the first or second rank in respect of GCA, depending on the year of the conducted evaluation. These are SP 163, SP 164, SP 170, SP 171 and SP 173 that have differed by their variability of the variants of SCA (from the low variants to the high ones). The highly productive testcross hybrids: Madonna M × SP 165 (4.88 t / ha), Madonna M × SP 171 (4.85 t / ha), Madonna M × SP 167 (4.80 t / ha), T 7M × SP 165 (4.78 t / ha) have been obtained based on the self-pollinated lines having invariably high figures of GCA and SCA

Combining ability with respect to “grain productivity” has been studied among thirty eight self-pollinated lines of maize of mid-early and early maturing in the system of hybrid combinations. The lines with high general (GCA) and specific (SCA) combinative ability have been hybridized. New high heterotic hybrids have been developed on the basis of lines with high GCA and SCA

Based on the analysis of the nature of some flowering test crosses which have been resulted in the hybridization with purposely chosen sterile sources (analyzers), the new self - pollinated lines of maize have been identified according to the content of fertility-restorer genes of ‘C’ type of CMS. Genotype of the line RD 257 - rf4rf4rf5rf5Ff6Rf6 (class II), genotype of the line RD 245 - rf4 rf4 Rf5 Rf5 rf6 rf6 (class III), genotype of the line RD 274 - rf4rf4Rf5Rf5Rf6Rf6 (class V), genotype of the line RD 231 - Rf4Rf4rf5rf5Rf6Rf6 (class VI ) genotype of the line RD 261 - Rf4Rf4Rf5Rf5Rf6Rf6 (class VII). The identification of the content of the alleles of fertility - restorer genes allows forecasting the nature of flowering hybrid progeny resulted in the hybridization with a known genotype. We have created a catalog of self - pollinated lines of maize according to the fertilityrestorer genes, which consists of 18 lines, which have been studied in all the years of research. We have identified the lines belonging to classes I, II, III, V, VI, VII and VIII. During the transfer of maize hybrids on a sterile basis the lines of classes I and VIII are those ones which have been of great interest. The self - pollinated lines KV 204, SP 286 (class I) are the reliable fixers of «C» type of CMS. The progeny resulted in the hybridization with any sterile lines is characterized by complete sterility. The new self - pollinated lines KV 498, KV 272, KV 227, SP 357, RD 261 (class VIII) are constant natural fertility-restorers. They are able to fully restore fertility in hybridization with any sterile lines and in any growing conditions