Donors of ultra-earliness for spring common wheat breeding

Knowledge of productivity and genetic control of the rate of ultra-early lines development will facilitate their use in breeding of common wheat Tritium aestivum L. for high adaptive capacity. The research focused on ultra-early lines Rico (k-65588), Rimax (k-67257) (progeny of F3 Rico × ‘Max’, k-57181), Fori 1-8 line series (progeny of F4 ‘Photon’ × Rico) and Rifor 1-13 (progeny of F7-8 Rico × ‘Forlani Roberto’), as well as on the accessions ‘Photon’ (k-55696) and ‘Forlani Roberto’ (k-42641). The varieties ‘Leningradskaya 6’ (k-64900) and ‘Leningradskaya 97’ (k-62935) were used as standards in VIR, and ‘Chelyaba 2’ (k-64379) was used in Сhelyabinsk ARI. The alleles of Vrn and Ppd genes were identified by PCR using the published allele-specific primers. Responses to vernalization (30 days at 3°C) and to a short 12-hour day were determined according to the VIR guidelines. The ultra-earliness of common wheat lines is associated with the presence of dominant alleles Vrn-A1, Vrn-B1, Vrn-D1, Ppd-B1, Ppd-D1, and possibly Eps. The shortest emergence-to-heading period at two experimental locations was noted for Rico (39.9 ± 1.49 days), which is 14.8 ± 1.22 days earlier than the development of region-adapted varieties. The Rico genotype contains Vrn-A1, Vrn-B1, Vrn-D1, Ppd-B1 and Ppd-D1. In the Rimax genotype, different alleles of the Ppd-D1 and Vrn-B1 genes were found, possibly being a result of recombination processes in Rico × ‘Max’ hybrids. Under a short photoperiod (12 hours), the Rico and Rimax genes can interact in a cumulative polymeric mode, which is not the case in long-day environments. Unlike other Rifor lines, Rifor 4 and Rifor 5, as well as ‘Forlani Roberto’, have a recessive vrn-A1a allele. However, Rifor 4 and Rifor 5 do not respond to vernalization, while ‘Forlani Roberto’ is responsive to this factor. The absence of response to vernalization in Rifor 4 and Rifor 5 possessing the recessive vrn-A1a allele is possibly provided by a complex of modifier genes along with the dominant Vrn-D1 gene, which was formed during recombination in F7-8 Rico × ‘Forlani Roberto’ hybrids. Recombinants of spring common wheat, combining ultra-earliness and relatively high ear productivity, have been identified. Grain yield per 1 m2 of new ultra-early lines in some years can reach 90% of that of the ‘Leningradskaya 97’. It is expedient to use ultra-early lines as donors of high-rate development in common wheat breeding, considering genetic peculiarities of the source lines.