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The intergenic spacer of ribosomal RNA genes in maize: Length heterogeneity in populations and use of the spacer as a molecular marker in breeding
Abstract
The goals of this study were to survey the variation for intergenic spacer length of the ribosomal RNA genes (rDNA) in maize populations and to evaluate its influence on agronomic traits. Materials surveyed for the variation of spacer length included 13 populations of maize. In order to test the correlated response of spacer length and agronomic traits, three subpopulations were established from each of the three base populations (Nebraska Krug (NK), Nebraska B (NB), and Nebraska Stiff Stalk (NS)) by divergent selection on the basis of spacer lengths characterized by Southern hybridization. Plants were classified based on the predominant pattern of Sac I restriction polymorphisms observed as the major fragments of 3.4, 3.6, 3.8, and 4.2 kb from the IGS regions in rDNA. Heterogeneity of spacer length was observed within the between maize populations as well as within individuals. The frequency of longest variant (4.2 kb) appeared to be increased in NS but not in NB population as a consequence of recurrent selection for improvement of grain yield and standability. Results also indicate that spacer variation was associated with selection. The frequency of spacer variants in subpopulations created by spacer length selection indicated that the frequency of spacer variants was shifted toward long (4.2 kb) and short (3.4 kb) directions by divergent selection. For copy number of ribosomal RNA genes, no significant difference was found among subpopulations created by selection for either longest or shortest spacer length. Observations of agronomic traits indicate that Long x Long subpopulations are taller and have greater seed weight than Short x Short in all three populations. Both days-to-flower and grain yield are also likely to be affected, although no significant differences were detected. Results of this work suggest that spacer length variation in maize populations might be usefully exploited in breeding programs.
Subject Area
Agronomy|Molecular biology
Recommended Citation
Huang, Sheng-Chung, "The intergenic spacer of ribosomal RNA genes in maize: Length heterogeneity in populations and use of the spacer as a molecular marker in breeding" (1991). ETD collection for University of Nebraska-Lincoln. AAI9121920.
https://digitalcommons.unl.edu/dissertations/AAI9121920