THE LOCATION OF GENETIC FACTORS CONTROLLING A NUMBER OF QUANTITATIVE CHARACTERS IN WHEAT

Abstract

Techniques based on the use of interval subsitutions in wheat were used to locate factors controlling a number of quantitative characters. Chromosome 7B of the variety Hope differs from that of Chinese Spring by four factors, ht, gw, gn and tl, determining the charactes height, grain weight, grain number and tiller number. By establishing siginifcant associations between these characters and four genetic markers previously located on this chromosome, the approximate positions were obtained of three of the factors, ht, gn and tl. Also, using a method based on the correlation coefficients between any two of the four chracters, estimates of recombination between the factors were derived. This provided strong evidence that the order was ht gw, tl gn along the chromosome. The recombination frequencies obtained by this method agree closely with those established by the use of the genetic markers. Since two of the markes are located on the long arm and two on the short arm of the chromosome, the location of the factors in relation to the centromere could be ascertained. In this way, ht and gw were found to be situated on the long arm and gn on the short arm, whereas tl could be on either arm but close to the centromere.