2008 Annual Report
1a.Objectives (from AD-416)
Develop scion cultivars of stone fruit, nuts, and grapes for fresh market and for dehydration with high quality and storage ability. Develop disease and pest resistant Prunus and Vitis scions and rootstocks. Develop genetic information to facilitate selection and enhance breeding efficiency.
1b.Approach (from AD-416)
Classical breeding techniques will be used to concentrate the expression of quantitative traits and to transfer newly available characteristics into adapted Prunus and Vitis germplasm for cultivar development. Populations will also be produced to determine the inheritances of specific discrete traits, and to develop marker assisted selection methods. Field trials will be used to confirm graft compatibility, and specific qualities of both rootstocks and scions. Greenhouse and field screening for resistance to nematodes, powdery mildew, and Pierce's disease will continue. Molecular markers will be identified that are closely linked to phylloxera resistance in grapes. A known marker for seedlessness will be tested in several lines of raisin and table grapes. Known markers for self-compatibility and self-incompatibility in almonds will be used to predict the compatibility status of new almond crosses. Markers for plum and apricot will be used to follow the recombination of the two genomes during production of a commercially viable interspecies cross. Formerly 5302-21220-003-00D (8/03).
The progress reported herein relates specifically to Component 3 (Genetic Improvement of Crops) of National Program 301 (Plant Genetic Resources, Genomics, and Genetics Improvement) in the evaluation of stone fruits (apricot, peach, nectarine and plum), almonds and grapes for potential introductions as new cultivars. Three flat shaped nectarine selections were submitted for virus indexing. A total of 90 apricot, 28 plum, 143 nectarine and 63 peach selections were evaluated. Six peach and three nectarine selections with flat shape fruit and three peach and 24 nectarine selections with round fruit were promising enough for larger tests. Five advanced apricot selections were sun-dried with cultivars ‘Goldensweet’ and ‘Patterson’ (drying standards) for color retention comparisons during long term storage. Three nectarine selections were evaluated for the first time in grower trails.
Sixty-one self-compatible and 30 self-incompatible almond selections were evaluated in 2007 for nut and kernel characters. Testing for self-compatibility during the 2008 bloom yielded over 60 new selections from which 49 will be evaluated for kernel qualities during the next harvest. Bloom and almond hull split phenologies were obtained for all existing self-compatible selections as well as important self-incompatible comparison cultivars. Stratification and soaking treatments were imposed on seedlots from three male-sterile peach-almond hybrids to evaluate possible improvements in seedling emergence.
A total of 113 seedless x seedless crosses for table, raisin, and powdery mildew resistant grapes were made. One hundred two table grape seedlings fruiting for the first time were selected for laboratory evaluation. Fifteen of these new seedless grape selections (5 red, 6 black and 4 white) were propagated in 25 vine advanced test plot. One mid-season red, two mid-season white, one early white, one early black and one mid-season black seedless selections show commercial promise. One hundred twenty three raisin grape seedlings fruiting for the first time were selected for laboratory evaluation. Another 147 raisin selections with natural dry-on-the-vine (DOV) potential were also evaluated. Fourteen new raisin selections were propagated into the natural DOV advanced test plot. Thirty one of 92 advanced DOV selections that fruited the first time in two vine plots had good raisin quality and drying ability. Modified backcrosses were continued to combine high fruit quality from table and raisin selections with the best powdery mildew resistant selections. Eighteen families from five sources of powdery mildew resistance were screened in the greenhouse. In the third backcross generation, resistance from V. romanetii is still segregating as a single dominant gene. From over 2,000 seedlings, 12 F1, 69 BC1 and 27 BC2 advanced table and raisin powdery mildew resistant selections were made. Thirty-eight have commercially acceptable aborted seeds and 7 were rated as the highest parents.
Genetic inheritance of powdery mildew resistance in grapes. Powdery mildew is the most devastating fungal disease of grapes with over 17 million pounds of sulfur used on table grapes alone in 2004. Natural resistance exists in wild grape species and can be used instead of chemicals to control powdery mildew. A Chinese grape species has been hybridized, by ARS scientists in the Crop Diseases, Pests and Genetics Research Unit in Parlier, CA, with raisin germplasm and resistance was inherited as a single dominant gene through the third backcross generation. This finding demonstrates that mildew resistance can be transferred to raisin, table or wine grapes while improving fruit quality in a modified backcross program. The potential impact is the development of powdery mildew resistant grape varieties. This accomplishment addresses NP 301 Plant Genetic Improvement of Crops; Problem Statement 3B – Capitalization on Untapped Genetic Diversity
Evaluating almond shell strength Almond processors classify almond varieties as being either hard or soft-shelled on the basis of kernel percentage, and use distinct cracking systems for each class. However, two almond varieties of similar kernel percentage may have different shell strengths because of differences in chemical composition, shell morphology or fiber content. Eight diverse almond varieties were evaluated in Crop Diseases, Pests & Genetics Research Unit laboratories for shell cracking strength, shell bulk density and kernel percentage in two consecutive harvest seasons. In some cases shell cracking strength was independent of the kernel percentage, suggesting varietal shell compositional or morphological differences. These findings provide researchers with a better understanding of which shell types are best suited to specific industrial processes for this large-volume agricultural by-product. This accomplishment addresses NP 301 Plant Genetic Resources, Genomics and Genetic Improvement; Component 3 - Genetic Improvement of Crops; Problem Statement 3B – Capitalization on Untapped Genetic Diversity.
5.Significant Activities that Support Special Target Populations
|Number of the New MTAs (providing only)||2|
|Number of Invention Disclosures Submitted||2|
|Number of Non-Peer Reviewed Presentations and Proceedings||5|
|Number of Newspaper Articles and Other Presentations for Non-Science Audiences||4|
Ledbetter, C.A. 2008. Shell Cracking Strength in Almond (Prunus dulcis [Mill.] D.A. Webb.)and its implication in uses as a value-added product. Bioresource Technology. 99(13): 5567-5573.
Ledbetter, C.A., Sisterson, M.S. 2007. Advanced Generation Peach-Almond Hybrids as Seedling Rootstocks for Almond: First Year Growth and Potential Pollenizers for Hybrid Seed Production. Euphytica. 160(2): 259-266.
Ledbetter, C.A. 2008. Breeding of Apricot. In: Temperate Fruit Crop Breeding Germplasm to Genomics. ISBN 1402069065
Ramming, D.W. 2008. ‘Thomcord’ grape. HortScience 43(3)945-946.
Ledbetter, C.A. 2008. Register of New Fruit and Nut Varieties List 44. HortScience 43(5):1321-1343.