The line Rico is the earliest maturing accession in the VIR collection of spring bread wheat

Background. To optimize the process of bread wheat breeding for earliness and environmental adaptability, searching for new source material is a crucial task. The ultra-early line Rico (k-65588) – Triticum aestivum var. erythrospermum Koern. – stands out among the bread wheat accessions from the VIR collection for its important adaptive features.Materials and methods. Spring wheat accessions with different speed of development were selected from the VIR collection for this study, along with the ultra-early lines Rifor 1 ... 10 (F6-7 Rico × Forlani Roberto k-42641) and Fori 1 ... 8 (k-65589 ... k-65596) (F4 Foton k-55696 × Rico). Their responses to a short 12-hour day were assessed. Vernalization conditions were 30 days at 3°C. The genetics of plant sensitivity to vernalization and photoperiods was studied using allele-specific primers for the genes Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1.Results and conclusions. In the Northwest of Russia, the period from seeding to heading for Rico plants was 39.9 ± 1.49 days, or 14.8 ± 1.22 days less than for the released commercial wheat cultivars. Among the 8400 wheat accessions, studied by the Wheat Genetic Resources Department of VIR in this area from 1948 to 2018, the shortest period from germination to heading was observed in the line Rico: 29 (28–30) days. The absence of response to vernalization in Rico, Fori and Rifor lines was determined by the dominant alleles Vrn-A1, Vrn-B1 and Vrn-D1. Photoperiodism in Rico and partially in Rifor was controlled by at least two genes: Ppd-D1 and Ppd-B1. In the F2 population of Rico hybrids with 8 wheat accessions no transgression was observed beyond the limits of Rico‘s variation. The difference in the development rate between Rico and other wheat accessions is controlled by two or three non-allelic genes. Rifor lines can compete in productivity with commercialized wheat cultivars

Comparative analysis of the inheritance of a high development rate in the Rimax and Rico lines of spring bread wheat (Triticum aestivum L.)

Background. Development of early-ripening spring bread wheat (Triticum aestivum L.) cultivars is an important task for Russian breeders. Knowledge of the genetics of ultraearly varieties – sources of valuable genes that determine an earlier-maturing type of plant development –will be used to work out methods for obtaining source material for breeding.Materials and methods. The ultra-early lines Rico (k65588, var. erythrospermum Koern.) and Rimax (k-67257, var. lutescens (Alef.) Mansf.), and cvs. ‘Max’ (k-57181, var. lutescens) and ‘Leningradskaya 6’ (k-64900, var. lutescens) were studied. Alleles of the Vrn and Ppd genes were identified by PCR according to known publications, and genomic DNA was isolated from 3-day-old seedlings by the CTAB method.Results. In the environments of Northwest Russia, the Rimax and Rico lines are characterized by the highest rate of development before heading among the spring wheat accessions from the VIR collection. In the Rimax and Rico genotypes, the Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1 genes were found. Genotypes with different alleles of Ppd-D1 and Vrn-B1 were identified in the Rimax line. Under conditions of a long day (18 hours), in the population of F2  (F3 ) Rico × Rimax hybrids, the ratio of phenotypes with a high development rate to all others was observed as 1 : 15 (χ2 1: 15 = 0.64). Under a short day (12 hours), 5 clearly tested groups were identified in F2 with the ratio 1 : 4 : 6 : 4 : 1 (χ2  = 3.03; χ2 0.05 = 9.48), which indicates the manifestation of cumulative polymerization.Conclusion. Each of the Rimax and Rico lines has two pairs of independent duplicated genes that determine a high development rate. Under short-day conditions, these genes can interact like cumulative polymers. The Rimax and Rico lines, due to their high development rate, are valuable source material to be used in breeding for earliness

Breeding and genetic aspects of creating productive forms of fast-developing spring bread wheat

Background. In Russia, wheat breeding should also focus on creation of earlier-maturing varieties with an optimal duration of the vegetation period reflecting territorial environmental features. It is very important to overcome the negative correlation between the early maturity and productivity of wheat. The present work was aimed at analyzing special features of genetic and physiological mechanisms of early maturity in spring wheat (Triticum aestivum L.) and at determining possibilities of creating recombinants with high development rate and plant productivity.Materials and methods. The study employed such ultra-early spring wheat accessions as 'Rico' (k-65588), 'Foton' (k-55696), 'Fori' lines (kk-65589 ... 65596) selected from F4 hybrids of 'Foton' x 'Rico', and 'Rifor' lines selected from F6-7 hybrids of 'Rico' x 'Forlani Roberto' (k-42641). Genetics of the development rate was studied using hybridological analysis and 'Triple Dirk' near isogenic lines. Photoperiodic sensitivity was evaluated under 18-hour (natural day) and at 12-hour (short day) conditions. Vernalization was performed within 30 days at 3°C.Results and conclusion. The ultra-early maturing accessions of spring wheat 'Rico', 'Foton', as well as 'Fori', 'Rifor 1', 'Rifor 6' and 'Rifor 7' lines had the shortest vegetation period in comparison with varieties from the VIR collection of plant genetic resources. These accessions had weak photoperiodic sensitivity and were insensitive to vernalization. The lines did not change their characteristics in different ecological conditions. Besides the Eps gene, Vrn-A1, Vrn-B1, Vrn-D1, Ppd-D1 and Ppd-B1 determined the rate of development of the ultra-early varieties 'Rico', 'Foton' and 'Fori'. Possibly, the Eps gene that controls ultra-earliness per se, is a set of polygenes (modifiers) with a low effect. No transgressive segregations in comparison with 'Rico' were recorded for the hybrids of the ultra-early 'Rico' with nine wheat varieties. A perspective cultivar 'Erythrospermum 25513' was created at the Chelyabinsk ARI with participation of 'Fori 7' line. 'Forlani Roberto' is a late variety, it responds to vernalization and photoperiod, and in good conditions its productive spike has 5-6 grains in the spikelet. The spring type of 'Forlani Roberto' is determined by the dominant gene Vrn-B1. The spikelet multi-seededness in productive 'Rifor' hybrids is determined by two or three genes and their expression depends on the environment. The selected ultra-early 'Rifor' lines have the number of grains per spike 1,5-2 times higher than in the parent line Rico, but the mass of grain per spike is below that of standard varieties. The yield per 1 m2 of Rifor 1, Rifor 8, Rifor 6 and Rifor 7 lines reached 81, 82, 84 and 94%, respectively, in comparison with the standard variety 'Leningradskaya 97'. Therefore, a possibility of creating wheat recombinants that combine ultra-earliness and high spike productivity is demonstrated