|Holland, Jim - Jim|
Submitted to: Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2009
Publication Date: 5/1/2010
Citation: Gonzalo, M., Holland, J.B., Vyn, T., Mcintyre, L. 2010. Direct Mapping Of Density Response in Recombinant Inbred Lines of Maize (Zea mays L.). Heredity. 104:583-599 Interpretive Summary: Breeding for adaptation to higher densities in maize has greatly increased maize yield potential per unit area. The genetic basis for this plant response to density is unknown. To understand the genetic basis of plant response to density in maize, we evaluated a population of inbred lines derived from the cross of inbred lines B73 and Mo17 for growth, development, and yield traits at moderate (50000 plants ha-1) and high (100000 plants ha-1) plant densities. Key gene regions affecting the response of these traits to higher densities were identified with the use of a genetic map. We verified the importance of these gene regions in an independent study of a subset of lines evaluated under large plot yield trial conditions in an independent environment.
Technical Abstract: Breeding for adaptation to higher densities in maize has greatly increased maize yield potential per unit area but the genetic basis for this plant response to density is unknown as is its stability over environments. To elucidate the genetic basis of plant response to density in Maize, we mapped QTL for plant density-related traits in a population of 186 Recombinant Inbred Lines (RILs) derived from the cross of inbred lines B73 and Mo17. All RILs were evaluated for growth, development, and yield traits at moderate (50000 plants ha-1) and high (100000 plants ha-1) plant densities. The results demonstrate that epistasis plays an important role in the genetic control of the traits evaluated, and in their response to density. Five of the 7 loci significant for final height showed clear evidence for epistatic interactions. Other traits such as days to anthesis, anthesis-to-silking interval, barrenness, ears per plant, and yield per plant all were affected by at least one epistatic interaction. Locus by density interactions are of critical importance for anthesis-to-silking interval, barrenness, and ears per plant. A second independent experiment to examine the stability of epistatic QTL for barrenness in a new environment clearly showed that epistatic interactions were stable across environments in their differential response to density. In this verification experiment the 4-locus QTL was used to choose lines with the 4 unfavorable alleles and compare them to the lines with 4 favorable alleles and the epistatic effect was confirmed.