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United States Department of Agriculture

Agricultural Research Service

Research Project: Improvement of Prunus and Vitis Scions for Fruit Quality and Pest Resistance

Location: Crop Diseases, Pests and Genetics Research

2013 Annual Report

1a. Objectives (from AD-416):
Develop and introduce new high quality and disease-resistant cultivars of almonds, grapes and stone fruits that will sustain American agriculture and supply high quality, nutritious fruits and almonds to U.S. consumers and international markets. 1. Continue evaluation of existing high-quality scion selections of stone fruit (apricots, nectarines, peaches, and plums) from the breeding program to identify those having desirable traits such as enhanced sugar content, novel peento flat shape and expanded ripening season, and table and raisin grapes with large seedless fresh fruit that stores and ships well, natural ‘dried on the vine’ raisin trait, economic production levels with spur pruning, and enhanced anthocyanin content for fresh and processing markets. 2. Identify Vitis accessions resistant to powdery mildew and evaluate existing table grape and raisin breeding populations and selections for high fruit quality with host-plant disease resistance. 3. Evaluate existing self-compatible almond accessions adapted to California.

1b. Approach (from AD-416):
Classical breeding techniques have been used to create segregating populations where the expression of quantitative traits has been concentrated and newly available characters have been transferred into adapted Prunus and Vitis germplasm. Plant materials in existing segregating populations of Prunus and Vitis will be selected and propagated for new cultivar development. Greenhouse and field screening will proceed to select Vitis seedlings with resistant to powdery mildew. The genetic control of raisins that dry on the vine and red flesh color in grapes will be determined through the evaluation of appropriate segregating progenies. Apricots will be selected for white flesh, for drying ability and for late maturity season from numerous segregating progenies. New self-compatible almonds will be selected having kernel qualities similar to Nonpareil, and four high kernel quality self-compatible almond selections will be trialed in isolated orchard conditions to evaluate the yield potential of self-compatible almonds in the absence of bee pollination. Formerly 5302-21220-004-00D (7/08).

3. Progress Report:
This is the final report for in-house project No. 5302-21220-005-00D. Research continues on cultivar development at this location through the new in-house project No. 5302-21220-006-00D. Stakeholders provided support for continued hybridizations of table and raisin grapes. During this project, over 920,000 emasculations were performed to create new table grape and raisin hybrids from parental vines. Powdery mildew (PM) resistant germplasm also has been used in hybridizations. Greenhouse screening was used to identify resistant seedlings prior to field planting. PM resistant vines were evaluated for fruit quality, and backcrossing of the PM resistant vines were accomplished through five generations. Natural dry-on-vine (NDOV) raisins have been identified. This character greatly increases efficiency of raisin production by reducing grower inputs (cane-cutting, tray drying). NDOV vines were used in hybridizations to create earlier-ripening and higher quality raisins. Nearly 100 NDOV selections are being evaluated in 2- or 7-vine plots. The NDOV trait also has been bred into PM resistant raisins, with four new NDOV PM resistant raisin selections added to 7-vine plots during 2012. Hybridizations in Prunus ceased after the 2008 bloom period. Remaining apricot seedling populations are being evaluated for late season fruit maturity and high quality drying types. Color retention in dry apricot has been used as an evaluation criterion, and numerous selections have been identified that retain the deep orange coloration better than California’s standard drying cultivar Patterson. Four self-compatible almonds were trialed under commercial conditions in the southern San Joaquin Valley for yield potential and kernel quality. Yield varied widely, with one self-compatible selection yielding similarly to the industry standard cultivar Nonpareil. Cumulative harvests from three successive years revealed varying degrees of high and low yield fluctuations in alternate years (alternate bearing) for the trialed almonds. A multivariate procedure was developed to separates Nonpareil Marketing Group almond kernels from kernels in other Marketing Groups. Discriminant analyses distinguished Nonpareil Marketing Group kernels from cultivar Carmel (California Marketing Group) and Padre (Mission Marketing Group) with less than 2% error using 16 kernel characters. The procedure can be used to identify almond accessions similar to Nonpareil in kernel shape and appearance. Twelve new cultivars were presented to growers during the life of this project. Valley Pearl and C51-63 were released as new table grapes, whereas Sunglo and Sunpreme are now available as new raisin cultivars. Three new apricots, Bolaroja, Primarosa and Twocot, are now available for propagation, with cultivar Twocot being used in either fresh fruit or dry production. Demko 10-17A was released as a new rootstock to provide grape growers with a nematode and phylloxera resistant stock that induced moderate vigor. Four new Prunus rootstocks (HBOK 10, HBOK27, HBOK 32 and HBOK 50) were introduced to provide growers with root knot nematode resistance and varying degrees of vigor reduction.

4. Accomplishments
1. 'Sunpreme' raisins dry themselves. Traditional tray-dried raisins may be a thing of the past when the new Sunpreme raisin comes into production. ARS researchers at Parlier, California, have developed ‘Sunpreme’, a new raisin grape that dries naturally on the vine without cutting canes. ‘Sunpreme’ is particularly well-suited for mechanical harvesting, thereby significantly reducing production costs. Unlike ‘Thompson Seedless’, the major grape variety used for tray-dried raisin production, ‘Sunpreme’ can be spur-pruned, further reducing grower inputs.

Review Publications
Ledbetter, C.A. 2012. Postharvest dried apricot color degradation of three California apricot accessions. Acta Horticulturae. 966:163-168.

Zhebentyayeva, T., Ledbetter, C.A., Burgos, L., Llacer, G. 2012. Apricots. In: Badenes, M.L., Byrne, P.H., editors. Fruit Breeding, Handbook of Plant Breeding, Vol. 8. Available: Springer Science & Business Media. p.875

Ledbetter, C.A., Mercure, E., Halasz, J., Hegedus, A. 2013. Yield, pollination aspects and kernel qualities of almond (Prunus amygdalus Batsch) selections trialed in the Southern San Joaquin Valley. Journal of American Pomological Society. 67(3):126-136.

Last Modified: 06/21/2017
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