|Holland, Jim - Jim|
Submitted to: Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2007
Publication Date: 5/10/2007
Citation: Gonzalo, M., Vyn, T.J., Holland, J.B., Mcintyre, L.M. 2007. Mapping reciprocal effects and interactions with plant density stress in zea mays l.. Heredity. 99:14-30. Interpretive Summary: Much of the improvement in yield of corn over the last century has been due to greater tolerance of stress. One of the key stresses that modern corn tolerates better than older varieties is the stress due to dense plantings. Previously, we mapped genome regions that affect this response in corn inbreds and hybrids and found that different traits are associated with improved yield under low and high planting densities. In this study, we extended the genetic analysis of plant density stress to determine the effects of specific genome segments on this response and, further, the effect of which parent (male or female) these segments were derived from. We found that the parent of origin effect was important for several early season traits, such as early vigor and plant height, and that this effect also depended on the planting density. These results highlight the importance of parent of origin effects on agronomically important traits in maize. The mechanism of these effects are not certain, but probably involve different forms of epigenetic marking of chromosomes derived from male or female parents.
Technical Abstract: Reciprocal effects are due to genetic effects of the parents (i.e. maternal and paternal effects), cytoplasmic effects, and parent of origin effects. These reciprocal effects have long been of interest to geneticists. However, the extent to which reciprocal effects exist, or can be attributed to specific components, remains under examination in several plant species. Modern molecular techniques provide new tools that can help dissect the genetic basis of reciprocal effects. Reciprocal effects have been reported by several investigators for various agronomic characters in different types of maize materials for grain and silage usage. Maize geneticists and breeders are aware of reciprocal effects, and have recognized them as a one source of genetic variability. Several genetic factors such as differences in the maternal genotypes, differences in endosperm DNA, differences in the sporophyte cytoplasmic DNA, and differences in the expression of the sporophyte nuclear DNA may contribute to differences between reciprocal crosses. However, there is little consensus in the literature concerning the relative importance and systematic exploitation of these effects in practical breeding programs. In this study, we developed an experimental design and statistical analysis to identify and characterize the contribution of specific nuclear chromosomal regions to reciprocal effects. We show how this approach model can be used to map the location of loci responsible for the reciprocal differences and we attempt to disentangle the forces driving reciprocal differences in a population of recombinant inbred lines of maize.