Date of Award


Document Type


Degree Name

Master of Science (MS)


Plant and Environmental Science

Committee Chair/Advisor

Ksenija Gasic

Committee Member

Christopher Saski

Committee Member

Juan Carlos Melgar

Committee Member

William C. Bridges Jr


Peach [Prunus persica (L.) Batsch] germplasm varies in heat requirement and bloom time. This variability can be utilized in breeding for targeted environment or overall climate resilience. Development of molecular tools to aid in targeted selection of dormancy related traits is needed to support breeding for these traits. This project furthers our understanding of heat requirement accumulation diversity and genetic control in peach.

Peach bloom date (BD) is determined by the dynamic relationship of temperature requirements, from the sequential fulfillment of chill requirement (CR) and heat requirement (HR). Knowledge of HR and its influence on BD would provide deeper understanding of the adaptation to climate change. However, the genetic background of HR and the interrelationships among CR, HR, and BD have received less attention due to the methodological difficulty in assessing HR independently of CR. The HR counts the thermal time from a threshold base temperature (Tb) that must be accumulated from chilling fulfillment until reaching full bloom using the growing degree hour (GDH) model. We hypothesize that peach germplasm has genetic variability for Tb and total heat accumulation. Therefore, an opportunity exists for breeding peaches with high Tb and/or HR for climate resilience. For this purpose, the objective of this work is to investigate the HR in peach germplasm by using different threshold base temperatures (Tb) and arbitrary chill point over eight years (2014–2021). The plant material BD spanned from 62 to 80 Julian Days (JD; BLUP) and included low and high CR genotypes. The HR BLUP ranged from 4808 to 7721 GDH (reference Tb) and was not significantly correlation with BD. However, positive correlations were observed between CR and BD, and HR and CR were negatively correlated.

In addition, bi-parental mapping population was utilized to map QTL regions associated with HR. Utilizing the phenotypic data for BD and HR from two seasons and previously developed highly-saturated linkage map of bi-parental population used to map climate related traits we discovered new major QTL associated with heat requirement on chromosome 7 and revealed a hotspot within this region associated with both BD and HR. QTLs for BD identified on linkage groups (LGs) 1 and 2, were also detected. Candidate gene analyses supported hypothesis of this region being a hotspot for eco-dormancy related traits, HR and BD. Results presented in this work provide a foundation for understanding genetics of these important phenological traits and development of the tools to select for targeted HR, to enable breeding cultivars with improved resilience to global climate fluctuation.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.