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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Crop Germplasm Research » Research » Research Project #424405

Research Project: Pecan Improvement through Breeding and Genetics

Location: Crop Germplasm Research

2014 Annual Report

The long-term goal of this project is to produce improved scion and rootstock cultivars for the U.S. pecan industry. The project will also elucidate genetic control of important pecan traits using traditional and molecular genetics techniques. Over the next 5 years we will focus on the following objectives: Objective 1: Develop new pecan scion cultivars with high yield, superior nut quality, and improved resistance to diseases and insects. Focus will be on early nut maturity to reduce impact of alternate bearing and improved resistance to pecan scab. Sub-objective 1A: Develop high yielding pecan scion cultivars with early nut maturity, improved nut quality, and superior disease and insect resistance. Sub-objective 1B: Elucidate the genetic control of key horticultural traits in pecan utilizing appropriate qualitative and quantitative techniques. Sub-objective 1C: Characterize kernel composition found in native pecans across the species range. Objective 2: Develop superior rootstocks with outstanding vigor and site adaptation for all pecan growing regions. Sub-objective 2A: Quantify heterosis in pecan. Sub-objective 2B: Screen diverse seedling rootstocks for resistance to the root knot nematode. Sub-objective 2C: Refine recognition of rootstock effects on phenology and nutrient accumulation, impacting regional deployment. Objective 3: Develop genetic markers for use in genotyping diverse Carya breeding lines. Sub-objective 3A: Develop scaffold framework for sequence alignment. Sub-objective 3B: Use Restriction-site Associated DNA sequencing (RADseq) techniques to conduct phylogeographic analysis on populations of native pecans.

Research objectives will be met by basic genetic research and by an intensive cultivar and rootstock selection program. Phenotypic breeding techniques, supplemented with molecular tools, will be used to develop and release new pecan scion cultivars with high yield and quality, exhibiting improved disease and insect resistance. Similar approaches will be utilized to develop superior pecan rootstocks with outstanding vigor and salt tolerance. Qualitative and quantitative techniques, in conjunction with molecular techniques, will be used to elucidate the genetic control of key horticultural traits in pecans. Genetic research conducted by this project will increase our knowledge of the genetic control of yield components, nut maturity, nut quality, tree size, and disease and insect resistance. The scion cultivar development component of the work will produce precocious, high-yielding, regular bearing, disease- and insect-resistant cultivars that also have high nut quality. Rootstock breeding activities will produce new rootstocks with improved vigor, uniformity, salt tolerance, disease and insect resistance, and specific geographical adaptation; and which will ultimately contribute to increased yields of grafted scions.

Progress Report
The long-term breeder for this project retired in FY 2013. Efforts to recruit a new breeder in FY 2014 were not successful; recruitment efforts are ongoing. Breeding work during FY 2014 was continued under the oversight of the Project Research Horticulturist. Work included making crosses in ongoing efforts to create improved pecan cultivars and rootstocks. Novel rootstock crosses were made based on results of flow cytometry evaluations of germplasm made in the sister project (6202-21000-036-00D). Scab screening procedures were revised by development of a high intensity screening nursery. Scab screening of controlled cross progeny seedlings was conducted; resistant seedlings were identified and will be subjected to additional testing. Greenhouse plantings were made of geographically diverse seed stocks of pecan and are being screened for tolerance to salinity. Selected materials from that population were distributed to a cooperator at Texas Tech University for inoculation with Tuber lyoni (pecan truffle); commercial production of pecan truffle in pecan orchards may be possible. Diverse seedling progeny have been phenotypically screened for resistance to black pecan aphid and outstanding individuals identified. Over 2700 seedlings were established in a Cotton Root Rot screening nursery in Uvalde, Texas, with cooperators at Texas A&M AgriLife Research. An orchard of diverse seedling pecan rootstocks was propagated by grafting and budding. Additional DNA sequences were added to the existing scaffold in the pecan draft genome sequence by cooperators at HudsonAlpha Genome Sequencing Center.


Review Publications
Lee, B., Zhang, R., Du, W., Grauke, L.J., McHugh, T.H., Zhang, Y. 2014. Expression, purification and crystallization of pecan (Carya illinoinensis) vicilin. Acta Crystallographica Section F: Structural Biology and Crystallization Communications. F70:1049-1052. DOI: 10.1107/S2053230X14012369.