Location: Crop Germplasm Research2016 Annual Report
1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
In FY 2016 work, methods for quickly and efficiently monitoring pollen viability were developed for routine application in the breeding program in conjunction with cooperators at Texas A&M University and a Chinese visiting scientist. Project objectives to develop new pecan scion cultivars (Objective 1) with the aid of improved genomic methods (Objective 3) were addressed through creation of a series of controlled crosses, in cooperation with a national team of pecan researchers. In efforts to meet project objectives of developing superior rootstocks (Objective 2), novel rootstock crosses were made based on results of flow cytometry evaluations of germplasm made available by the sister project (3091-21000-036-00D). Scab disease screening procedures for use in replicated test orchards were refined by adoption of aids for estimating worst expression of leaflet and nut scab on a continuous scale, and by increasing the numbers of within canopy ratings. Scab screening of controlled cross progeny seedlings was conducted in nursery blocks, and apparently resistant seedlings were identified for additional testing. More than 2000 seedlings in a cotton root rot screening nursery in Uvalde, Texas, were monitored for late season leaf phenology and tissue samples were collected for DNA extraction in cooperation with cooperators at Texas A&M AgriLife Research. Cooperative research by a national team was undertaken in order to complete template genome sequences initiated by cooperators at HudsonAlpha Genome Sequencing Center.
5. Significant Activities that Support Special Target Populations:
Zhang, Y., Lee, B., Du, W., Fan, Y., Lyu, S.C., Nadeau, K.C., Grauke, L.J., Zhang, Y., Wang, S., Mchugh, T.H. 2016. Identification and characterization of a new pecan [Cara illinoinensis (Wangenh.) K. Koch] allergen, Car i 2. Journal of Agricultural and Food Chemistry. 64:4146-4151.