|Baker, Kendra -|
|Chaparro, Jose -|
Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2012
Publication Date: May 1, 2013
Citation: Baker, K.M., Chaparro, J.X., Beckman, T.G. 2013. Detection of seed dormancy QTL in three F2 families of peach (Prunus persica). Tree Genetics and Genomes. 9(3):659-668. Interpretive Summary: The winter chilling requirement of a peach variety is a key characteristic influencing its adaptation and cropping reliability in different growing areas. A chilling requirement too high or too low for a growing location’s climate will severely impact a variety’s cropping ability. Early elimination of peach seedling hybrids with an inappropriate chilling requirement is a priority in most breeding programs. However, determining the chilling requirement of a new peach selection is typically done by observing its bloom date relative to known standard varieties. Unfortunately, new seedling varieties rarely bloom before their 3rd growing season delaying the decision making process in a breeding program. It has been observed that a peach seed’s stratification requirement is somewhat correlated with the resulting tree’s chilling requirement which suggests that a seed’s germination time might predict its winter chilling requirement. This work identified several molecular markers associated with seed stratification requirement and germination date, one of which appears to be in the same region as a marker associated with flower bud chilling requirement in peach. This work may pave the way to a the development of the markers needed to predict seedling chilling requirement as needed by breeding programs.
Technical Abstract: Dormancy is a condition that delays or inhibits growth in seed, vegetative buds, and floral buds. In peach, seed germination occurs when seed accumulate sufficient stratification and growing degree hours to break dormancy and begin growing. Correlations have been reported between mean seed stratification requirements and mean bud chilling requirements among Prunus families, but an individual seed’s germination date and subsequent vegetative and floral bud break date are not correlated. Prior to this study the genetic factors involved in regulating seed dormancy and their location on the peach genomic map were unknown. Segregating F2 seed were collected from a high x low chill F1 peach hybrid in 2005, 2006, and 2008. Germination date and growth habit was measured after the stratification requirement of the 2005 seed was fully met. The seed collected in 2006 and 2008 received varying amounts of stratification, which enabled data on stratification requirement, heat requirement, and growth habit to be collected. Genomic DNA from resulting plants was extracted and screened with SSR markers selected from the Prunus reference map at an average resolution of 20cM. Seed dormancy QTL were detected on G1, G4, G6/8, and G7. The QTL detected on G7 was discovered in the same region as a QTL associated with floral bud chilling requirement in peach.