2012 Annual Report
A central theme is identifying appropriate conservation targets that capture desired genetic diversity, remain viable during storage and are available to the user when needed. A conservation target is a group of propagules (such as seeds or pollens) or an individual propagule (such as an explant) that comprises an accession valued for specific genes, genetic richness (number and frequency of alleles) or an allelic combination (genotype). PGPRU scientists and their collaborators will investigate major conceptual issues of repository biology and standardization using within-unit expertise in biophysics, plant physiology, cell and molecular biology and population genetics and National Plant Germplasm System (NPGS) curators’ expertise on reproductive biology, phenotypic diversity, history and cultivation of their assigned collections. Our central position within NPGS allows us to develop protocols and predictive tools that are applicable to a wide variety of species and propagules.
Research on seed quality and storage behavior suggests that desiccation damage in developing embryos is related to the amount of mechanical disruption when cells shrink during drying. Damage decreases as embryos mature and this can be explained by accumulation of dry matter into cells. The results lead to a quantitative description of seed storage physiology that replaces existing categories of orthodox and recalcitrant behavior. Assays that measure molecular mobility within seeds are providing promising tools for predicting seed longevity or describing the early effects of aging continue to expand. Dynamic mechanical analysis (DMA) detects interactions of moisture and temperature on the tendency for molecular mobility in seeds.
Assessments of the effectiveness of genebanking are critical to support the high priority of wild-collected accessions. Tools that quantify genetic erosion within genebanked samples are being developed using barley. Collections of original wild populations were made and genetic diversity of these will be compared with accessions that have been stored and regenerated for more than 20 years in different genebanks using different genebanking strategies. This experiment complements additional research projects that integrate geospatial modeling and population genetic in order to estimate local adaptation. Advanced statistical methods to estimate genetic structure and Geographic Information Systems mapping have been used to detect patterns of diversity and help locate potential gaps in collections. The results from these projects have particular application to finding gaps in the representation of genetic diversity of species within a genebank.
Volk, G.M., Richards, C.M. 2011. Integration of georeferencing, habitat, sampling, and genetic data for documentation of wild plant genetic resources. HortScience. 46(11): 1446-1449.
Dierig, D.A., Wang, G., Crafts-Brandner, S.J. 2012. Dynamics of reproductive growth of Lesquerella (Physaria fendleri) over different planting dates. Industrial Crops and Products. 35:146-153.
Wegrzyn, J.L., Main, D., Figueroa, B., Choi, M., Neale, D.B., Jung, S., Stanton, M., Zheng, P., Ficklin, S., Cho, I., Peace, C., Evans, K., Volk, G.M., Oraguzie, N., Chen, C., Gmitter, F.G., Abbott, A.G. 2012. Uniform standards for genome databases in forest and fruit trees. Tree Genetics and Genomes. 8:549-557.
Ballesteros, D., Estrelles, E., Walters, C.T., Ibars, A. 2012. Effects of temperature and desiccation on ex situ conservation of nongreen fern spores. American Journal of Botany. 99(4): 721-729.
Gross, B.L., Henk, A.D., Forsline, P.L., Richards, C.M., Volk, G.M. 2012. Identification of interspecific hybrids among domesticated apple and its wild relatives. Tree Genetics and Genomes. 8(6):1223-1235. DOI: 10.1007/s11295-012-0509-4.
Perez, H.E., Hill, L.M., Walters, C.T. 2012. An analysis of embryo development in palm: interactions between dry matter accumulation and water relations in Pritchardia remota (Arecaceae). Seed Science Research. 22:97-111.
Gross, B.L., Volk, G.M., Richards, C.M., Forsline, P.L., Fazio, G., Chao, C.T. 2012. Identification of “duplicate” accessions within the USDA-ARS National Plant Germplasm System malus collection. Journal of the American Society for Horticultural Science. 137(5):333-342.
Routson, K.J., Volk, G.M., Richards, C.M., Smith, S.E., Nabhan, G.P., De Echeverria, V.W. 2012. Genetic variation and distribution of Pacific crabapple. Journal of the American Society for Horticultural Science. 137(5):325-332.
Volk, G.M. 2011. Chapter 25: Collecting pollen for genetic resources conservation. In: Guarino, L., Ramanatha Rao, V., Goldberg, E., editors. Collecting Plant Genetic Diversity: Technical Guidelines. 2011 Update. Rome, Italy: Bioversity International. Available: http://cropgenebank.sgrp.cgiar.org/index.php?option=com_content&view=article&id=654
Reeves, P.A., Panella, L.W., Richards, C.M. 2012. Retention of agronomically important variation in germplasm core collections: implications for allele mining. Theoretical and Applied Genetics. 124(6) 1155-1171. DOI: 10.1007/S00122-011-1776-4.