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Breeding Value of the X‐Ray Induced Macro‐Mutant. I. Variations Among Normal Appearing F2 Families Segregated From Crosses Between Macro‐Mutants of Peanuts ( Arachis hypogaea L.) 1
Author(s) -
Emery D. A.,
Gregory W. C.,
Loesch P. J.
Publication year - 1964
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1964.0011183x000400010027x
Subject(s) - geneticist , agricultural experiment station , arachis hypogaea , crop , south carolina , library science , biology , agriculture , ecology , genetics , political science , agronomy , computer science , public administration
D. A. Emery, W. C. Gregory, and P. J. Loesch, Jr. BECAUSE of its striking appearance and usually accompanying low vitality the X-ray induced macro-mutant has been the source of much speculation concerning the deleterious character of induced mutations. Little attention has been given to the genetic worth of mutations occurring in the background genotypes of induced macro-mutants. Extreme variability in various quantitative characters has been noted among X-ray mutants of the same phenotypic class within the same inbred line of peanuts (Gregory 2, 3, 4) and reviewed by Loesch (8). These observations caused Gregory to hypothesize (4) "that along with the macro-mutants produced by radiation a very large number of small varieties of both incremental and decremental characters has been produced and that these variations can be utilized in a selection program". Similar conclusions were reached by MacKey (9). Gregory further postulated (5) that the widespread occurrence of these grades of expressivity in the morphological mutants and the graded series via irradiation suggested non-allelic modifying effects possibly from the same linkage group. The hypotheses described were deemed reasonable by Loesch (8) since the induction of a single mutation could not be accomplished without simultaneously exposing the background genotype. It would also hold that segregates of a given morphological mutant from crosses between that mutant and an array of other X-ray induced mutants from the same autogamous line would differ as a function of the segregating backgrounds. In keeping with the latter statement, Loesch (8) concluded that the mutant grade variability in the peanut was a result of the multimutated background genotype after rinding statistical differences of significance among and within hybrid families of the same phenotypic class. Barring crossovers, the direct descendents of chromosomes bearing the original mutated loci were included in Loesch's experiments. This was necessitated by the use of deleterious markers in the evaluations. Genetic variances in the quantitative traits measured among backgrounds could, therefore, result from genes linked to or under the pleiotropic effects of the major gene.