CYTOGENETIC STUDIES ON TRITICALE. I. A METHOD FOR DETERMINING THE EFFECTS OF INDIVIDUAL SECALE CHROMOSOMES ON TRITICUM

Abstract

H E production of fertile, true-breeding hybrids which combine the T characters of two different species or genera has proven to be of theoretical and practical importance. These hybrids have usually arisen through a doubling of the chromosome complement following the initial cross, this doubling resulting in the presence in the fertile hybrid of two full complements from each parent. Such plants are known as amphidiploids because the chromosome set of each of the two parents is present twice, or in the diploid condition. I t is possible, however, to combine characters of two species or genera by a method which involves the addition of one or more chromosomes from one species to the full diploid complement of the other species. When the chromosomes of one species have desirable and undesirable dominant characters distributed among the various chromosomes of the set, these characters are given to the second species without selection in the amphidiploid. If only the chromosomes with the desired dominant characters could be added to the chromosome complement of the second species, the value of the combination for theoretical and practical purposes would be greatly enhanced. Such combinations have been secured between Secale and Triticum, and the method by which they were obtained should be applicable to other genera where an amphidiploid is available.