Change in ribosomal DNA spacer-length composition in maize recurrent selection populations. 2. Analysis of BS10,...

Area of Science:

• Plant genetics
• Molecular biology
• Agricultural science

Background:

• Maize (Zea mays L.) grain yield improvement is crucial for food security.
• Understanding the genetic basis of yield is essential for developing superior crop varieties.
• Ribosomal DNA (rDNA) intergenic spacer (IGS) regions exhibit variation and can be used as molecular markers.

Purpose of the Study:

• To investigate molecular variation in maize rDNA IGS among populations selected for grain yield.
• To determine if selection for grain yield impacts rDNA IGS variation and hybridization fragment (HP) patterns.
• To explore the potential association between rDNA HPs and grain yield in US Corn Belt environments.

Main Methods:

• Four maize populations (BS10, BS11, RBS10, RSSSC) were analyzed at initial and advanced cycles of selection.
• Molecular variation in the rDNA IGS was assessed using ribosomal spacer-length variants (rslvs) and a polymorphic SstI restriction site.
• Hybridization fragment (HP) patterns, representing combinations of rslvs and restriction sites, were identified and their frequencies quantified.

Main Results:

• Five rslvs and one polymorphic restriction site were detected, resulting in 20 distinct HP patterns.
• Significant changes in rslv and HP frequencies were observed between selection cycles in RSSSC, RBS10, and BS11 populations.
• Two specific HPs became more frequent in advanced cycles, with frequency changes being more pronounced for HPs than for rslvs.

Conclusions:

• Selection for grain yield significantly altered rDNA IGS HP frequencies in most maize populations studied.
• These findings support the hypothesis that specific rDNA HPs or linked loci are influenced by selection for grain yield.
• RDNA HPs may be associated with a selective advantage in maize grown in US Corn Belt environments, offering potential as molecular markers for breeding.