Location: Crop Diseases, Pests and Genetics Research
2018 Annual Report
Objectives
The long-term goal of this project is development and introduction of new, high-quality and disease resistant cultivars of Prunus (almond and apricot) and Vitis (table grapes and raisins) that will sustain American agriculture and supply high quality, nutritious fruits and nuts to U.S. consumers and international markets. Further, the project will strive to identify molecular markers linked sufficiently close to fruit quality traits of interest such that marker-assisted selection will be possible in future breeding efforts. Specifically, during the next five years we will focus on the following objectives:
Objective 1: Enhance breeding efficiency for table grape fruit quality, and other priority traits, by identifying associated molecular markers, and through trials, to determine commercial acceptability of advanced table grape selections.
Sub-objective 1A: Develop segregating populations and map fruit quality traits related to flowering time, rachis architecture, and berry size.
Sub-objective 1B: Through trials, determine commercial acceptability of advanced table grape selections.
Sub-objective 1C: Identify sources of resistance and develop molecular markers associated with resistance to Botrytis cinerea.
Objective 2: Develop durable resistances to powdery mildew and Pierce’s disease in table grapes and natural dry-on-vine raisins.
Sub-objective 2A: Develop durable resistance to powdery mildew in table grapes and natural dry-on-vine raisins.
Sub-objective 2B: Identify sources of durable resistance to Pierce’s disease and determine the relative susceptibility of existing commercial cultivars.
Sub-objective 2C: Develop table grape and natural dry-on vine raisin cultivars with durable resistance to Pierce’s disease.
Objective 3: Develop, select, and evaluate new, high quality scions of Prunus, e.g., high yielding self-compatible almond and glabrous-skinned apricot.
Sub-objective 3A: Develop, select, and evaluate new high-yielding self-compatible almonds.
Sub-objective 3B: Develop, select, and evaluate new glabrous-skinned apricots.
Approach
Classical breeding has been used to create segregating populations in Prunus and Vitis where the expression of quantitative traits has been concentrated and newly available characters have been transferred into adapted germplasm. New segregating populations will be created in Vitis to develop molecular markers for fruit quality traits, rachis architecture, resistance to Botrytis, flowering time and berry size. Advanced table grape selections will be compared for production timing and fruit quality after cold storage with existing table grape cultivars through public fruit showings held during each ripening season. Commercially acceptable advanced table grape selections will be introduced as new cultivars through consensus evaluation with the table grape industry.
New powdery mildew resistance sources will be evaluated in established segregating populations, and resistant accessions will be backcrossed with high quality table grapes and natural dry on the vine raisins as molecular markers are being developed. These new resistance sources will be used along with other mapped PM resistance sources in hybridizations designed to stack the resistances for durability. Empirical screening of Vitis germplasm for reaction to Xylella fastidiosa will continue, and existing commercial table grape cultivars will be evaluated for their relative susceptibility to Pierce’s disease. Crosses will be conducted to stack Xf resistances from Vitis arizonica and southeast U.S. Vitis germplasm into hybrids with high product quality. Promising high quality accessions with will be evaluated for survival and productivity in regions with high Pierce’s disease pressure.
In Prunus, hybridizations will be performed to identify and select new high-yielding self-compatible almonds that are California-adapted and have Nonpareil-like kernel characteristics. Apricot populations will be developed through hybridization among glabrous-skinned accessions, and new glabrous apricots will be evaluated for fruit quality and productivity. Newly-available glabrous-skinned apricot accessions from Kyrgyzstan will be propagated when available from plant protective quarantine and used in hybridizations to assist in the glabrous-skinned apricot breeding effort.
Progress Report
This report documents progress for project 2034-21220-007-00D, which started in May 2018 and continues research from project 2034-21220-006-00D, "Genetic Improvement of Prunus and Vitis Scions and Rootstocks for Fruit Quality and Pest Resistance."
In support of Sub-objective 1A, a mapping population segregating for rachis architecture and berry size was evaluated for time to anthesis on five clusters per vine this spring. Images of clusters and rachis collected in FY17 are being analyzed. A new mapping population segregating for cluster architecture (Cabernet Sauvignon x Rangspray) was planted in the field to be evaluated in 2020.
In support of Sub-objective 1C, a mapping population with potential segregation for Botrytis cinerea resistance was developed.
For Sub-objective 2A, evaluation of powdery mildew reaction continues in four new grape mapping populations. Approximately, 1,100 vines are scored for resistance/susceptibility to powdery mildew on leaves, stems, rachis, and grape berries. Selected vines found without traces of powdery mildew on these organs have been used in backcrosses with high quality table grapes and raisins. These unique powdery mildew resistance sources will be maintained separately until a marker is available for the resistance source.
In support of Sub-objective 2B, cuttings of table grape varieties, breeding lines, and grape species were collected for evaluations for susceptibility to two isolates of Xylella fastidiosa. Grape cuttings have been collected from known and putative sources of resistance to Pierce’s Disease and are currently being rooted for disease evaluations.
Accomplishments
