Project Number: 8080-21000-033-000-D
Project Type: In-House Appropriated
Start Date: Apr 27, 2023
End Date: Apr 26, 2028
Objective 1: Discover the genetic and molecular mechanisms that underlie tree architectural traits in fruit crops. Sub-objective 1A: Evaluate transgenic TAC1-silenced and LAZY1-silenced plum germplasm with different architectures for their potential use in novel growing systems. (Hypothesis) - Trees having more upright (TAC1-silenced) or horizontal (LAZY1-silenced) branch angles will be amenable to novel growing systems and enable ,high-density orchard systems. Sub-objective 1B: Integration of a narrow leaf (NL) trait into diverse canopy types to study the role of leaf size/shape in tree productivity. (Hypothesis) -The NL trait will improve light penetration and productivity, particularly within peach tree architectures having dense canopies. Objective 2: Identify genes for pitless and robust flavor traits and incorporate into stone fruits breeding. (Hypothesis)- The naturally occurring stoneless trait in plum is conferred by a single dominant mutation. Objective 3: Identify and characterize genes associated with resilience to climate change, spring frost injury, and associated abiotic stresses. Sub-objective 3A: Study the role of individual DAM genes within a set of specially designed plum transgenic lines. (Hypothesis) DAM genes have sub-functionalized in Prunus to precisely couple chilling and heat requirements to flowering time in flower or vegetative buds. Sub-objective 3B: Create a set of Apple transgenic lines with altered DAM gene expression to compare to DAM gene sub-functionalization in Prunus. (Hypothesis) DAM genes function differently in Malus compared to Prunus regarding chilling and heat requirements for flowering time. Objective 4: Breed improved pome and stone fruit cultivars that combine disease resistance, enhanced production, and high fruit quality traits. The Unit has active conventional breeding programs in stone and pome fruits that have multiple long-term goals. Specific efforts that will be accomplished within the proposed 5-year project plan are detailed below. Sub-objective 4A: Generate high-quality super sweet nectarine varieties and phenotype segregating populations for genetic mapping. Sub-objective 4B: Develop late-flowering peach/nectarine cultivars, characterized parental germplasm for breeding late flowering traits, and associated mapping populations and genomic information to facilitate future breeding efforts. Sub-objective 4C: Develop new pre-breeding apple lines and varieties with stacked traits related to fruit quality, productivity, and abiotic stress-resilience into disease-resistant backgrounds. Sub-objective 4D: Develop pear varieties with improved fruit quality, storage, and supply-chain resilience traits in disease-resistant backgrounds.
This project leverages plant breeding, genomics, genetics, molecular biology, and biotechnology strategies to address fundamental problems facing tree fruit production. The variety development and basic research activities are synergistic as the germplasm developed through the breeding efforts serve as a critical resource for identifying the genetic basis for important production traits. Many of the objectives will leverage the unique plant transformation capabilities of the unit coupled with available genome sequences for several tree fruit species. For Obj 1, tree architecture will be studied by evaluating horticultural characteristics of plum tree mis-expressing the TAC1 and LAZY1 genes. Collectively, these data will provide important practical information about how IGT genes contributes to tree shape. For Obj 2,technology to breed or engineer stoneless fruits will be developed by identifying the gene responsible for a naturally occurring stoneless trait in plum. In Obj 3, regulation of flowering time will be investigated using genetic, molecular, biotechnology, and next generation sequencing-based strategies. The breeding efforts in Obj 4 will include: 1) a novel super sweet trait in peach/nectarine that confers extremely high brix will be bred to develop commercial quality super sweet varieties; 2) peaches with delayed bloom will be developed by introgressing a naturally occurring late blooming trait, 3) Apple breeding will leverage the existing rapid cycle breeding system to intogress traits from wild germplasm and them stack key traits into parental germplasm including fire blight and scab resistance along with crisp fruit texture and superior flavor, and 4) in pear, we will leverage our unique germplasm to integrate fire blight resistance with important fruit quality characteristics. Collectively, these efforts will fill in key knowledge gaps about fundamental fruit tree developmental processes, provide new technologies for developing fruit tree germplasm with economically important traits, and lead to the development of new fruit varieties with superior traits.