Flowering in the Garden Pea: Expression of Gene Sn in the Field and Use of Multiple Characters to Detect Segregation1

Publisher Website
Google Scholar
Abstract
The major flowering locus, sn, was previously identified in the garden pea with the aid of special environmental conditions. The present study examines the effect of segregation for the Sn/sn pair of alleles in an F2 grown under field conditions. The dominant allele, Sn, caused a substantial increase in the time to first open flower, number of reproductive nodes and seed yield. Gene Sn generally increases the nodeo f first flower but this effect was minimized in the present F2 by choosing a particular genetic backgrounwd hich would allow emphasis on other important characters influenced by Sn. The increased time to open flower arose largely from the fact that Sn slowed the rate at which the flower buds developed relative to the rate of leaf expansion. A new variable, flower/leaf relativity (FLR), was devised to describe this effect in quantitative terms. Flower/leaf relativity proved to be the most effective of all the variables measured at discriminating Sn and sn segregates. However, none of the individual variables gave a clear‐cut separation between the Sn and sn segregates, which were positively identified by growing F3 progeny in controlled‐environment conditions. Certain two‐way data plots, e.g. seed yield/FLR, improved the chance of correctly distinguishing the two genotypes. Complete separation of the two genotypes, with the exception of one aberrant plant, was obtained by using six variables and either of two multivariate statistical techniques; a Principal Components analysis or a single Canonical Variate designed to maximally discriminate between the two genotypes. The results show that multivariate statistics can help to identify segregates where a major gene influences several characters in a quantitative manner.