Chromosome Substitutions with Dominant Loci Vrn-1 and their Effect on Developmental Stages of Wheat

Wheat substitution lines which change winter to spring growth habit were obtained due to substitutions of homoeologous group 5 chromosomes carrying dominant genes Vrn-A1, Vrn-B1 and Vrn-D1 into the genetic backgrounds of the winter varieties Zdar (sensitive to photoperiod) and Košutka (insensitive to photoperiod), and thus replacing the recessive alleles vrn-A1, vrn-B1, vrn-D1 by dominant alleles. The influence of the substituted chromosomes carrying individual loci Vrn on developmental stages of wheat was studied. The verified donor wheat varieties of dominant Vrn loci were: Zlatka (Vrn-A1, chromosome 5A), Česká Přesívka (Vrn-B1, chromosome 5B), and Chinese Spring (Vrn-D1, chromosome 5D). The six substitution lines were sown in the field on 10 subsequent dates and their developmental stages were checked to study the effect of the substitutions on development. The lines were also grown under short day conditions (10 hours) to evaluate their photoperiod sensitivity. The analysis of results confirmed the marked effect of chromosome 5A carrying the Vrn-A1 locus on duration of the developmental stages, besides the influence of sowing date and genetic background. The most shortening effect on growth stages was observed in the lines with substitutions of chromosome 5A (Vrn-A1) while the least reduction was in the lines with the substituted chromosome 5B (Vrn-B1). The largest difference in heading time, 6.5 days, occurred between the lines with chromosome substitutions carrying Vrn-A1 and Vrn-B1 loci. The effect of substitutions with Vrn-D1 was intermediate.  

Chromosomal effects on In Vitro morphogenesis in Wheat intervarietal Substitution Lines

The effect of individual chromosomes on in vitro morphogenic ability of immature embryos was studied using a Chinese Spring/Timstein substitution series. For this purpose 20 wheat lines of Chinese Spring with consequently substituted chromosome pairs from the cultivar Timstein together with the two parental cultivars were investigated. The regeneration ability of the studied lines was quantified by two parameters: frequency of regenerative calli and coefficient of propagation. The influence of the 5A, 1B and 4D chromosomes on in vitro morphogenesis was determined and the effect of 2A, 3A, 3B, 4B, 6B and 1D chromosomes, reported by other authors, was confirmed. The data indicated that the intervarietal substitutions of certain chromosomes caused significant variation in the number of morphogenic calli and recovered regenerants, in spite of the fact that the two parental cultivars were of similar morphogenic ability. This probably reflects the allele variation in a given locus on these chromosomes and/or background effect. The data suggest that the chromosome substitutions may have different compensatory effects depending on the similarity of the corresponding chromosomes and also on the possibilities of their expression in an alien genetic background.