Using the method of natural samples for studying the variability in sugar beat (Beta vulgaris L.) agamospermous seed progeny

The existence of natural genetic and natural mixed samples of seeds was theoretically grounded and experimentally demonstrated. A natural genetic sample is detected when analyzing the seed agamospermous progeny in the sequence coinciding with the sequence of seed setting, i.e., in the order they are located on a branch. The method of natural genetic samples has demonstrated the presence of individual regions with nonrandom distribution of phenotypic classes of agamospermous seeds on the branches of sugar beet plants. This phenotype distribution reflects the state of somatic cells on extended branch regions and the manifestation of this state in seed-bud cells. In turn, the genotype of each seed reflects the state of the seed-bud cell (apozygote) that gave rise to embryo development. We also demonstrated heterogeneity in the ratios of enzyme phenotypes of the seeds set on individual branches, regarding it as a result of the changes arising in somatic tissues at the moment of branching. Analysis of the ratios of seed phenotypes on individual branches of the same plant was named the method of natural mixed samples. The combination of natural genetic and natural mixed samples provides for identifying and analyzing various modes of seed setting (gamospermy and agamospermy) and studying the factors that influence the variability in these processes. We postulated that the nonrandom distribution and ratio of the seed phenotypes on plant branches resulted from a nonrandom endoreduplication of the homologous regions in homologous chromosomes carrying the marker locus alleles.