Barbara Christ, Ph.D.

Areas of Interest

Breeding potatoes with disease resistance, examination of pathogen variability and epidemiology of potato diseases

Program Interests

My research is focused on potatoes including breeding and disease management, which covers adapted research to provide information to growers as well as research into basic understanding of inheritance of disease resistance. There are five overall objectives to my program.

Objective 1: Develop and screen potato breeding lines to develop and release new varieties adapted for Pennsylvania growing conditions.
We have co-released ten potato cultivars and collaborated in the release of three other cultivars. We have also assisted breeders in identifying germplasm to be used as parents in future crosses. The germplasm is evaluated for yield, adaptability to specific environmental conditions, disease resistance, processing traits such as suitability for chipping and French-frying, and culinary traits such as baking and boiling. We continue to release new cultivars that are suitable for Pennsylvania production.

Objective 2: Develop disease-resistant potato germplasm.
We have developed methods and field plot designs to minimize inter-plot interference, enhance disease development and reliably evaluate germplasm for disease resistance. This has led to collaborative research on diploid potato populations that carry high levels of resistance to numerous diseases. I, in collaboration with Dr. Haynes, have determined that one diploid population has high heritability for late and early blight resistance and that there may be some resistance genes in common. We have expanded the disease resistance research with the addition of several other populations and now are examining powdery scab, common scab and Fusarium tuber rot resistance.

We have shifted efforts to include using molecular techniques to locate the resistance genes. We have developed a framework map of our diploid population using markers (RFLP, AFLP, SSR, and resistance gene probes) to determine where the resistance genes are located and then, using marker-based selection, to accumulate the genes into one genetic background.

Objective 3: Examine the genetic variability within potato pathogen populations and understand the biology of these organisms.
Another goal is to document the entire life cycle of the powdery scab organism and develop methods to detect this organism. Very little is known about this organism. Our research focuses on basic epidemiological studies to determine the environmental conditions conducive to disease development. We are also characterizing the disease reaction in hopes of developing disease resistant cultivars. Little is known about alternative hosts. We have developed a detection technique to quantify inoculum and/or identify disease on alternative hosts. There are no adequate control measures for this disease, and disease resistance may be the only alternative.

We are also examining genetic variation in Alternaria solani populations and more recently we have been examining them for sensitivity to fungicides.

Objective 4: Develop methods to detect and/or forecast potato diseases and develop integrated pest management strategies for potatoes in Pennsylvania.
The fourth goal is to develop a comprehensive integrated pest management system for potatoes. We have incorporated a disease-resistance factor into a forecasting scheme to reduce the number of fungicides applied to resistant potato cultivars. We continue to explore novel methods for gathering and disseminating weather data and information on probability of disease occurrence.

Objective 5: Evaluate new fungicides for efficacy toward potato diseases.
In response to the potato industry, we have developed a testing program for fungicides to be better able to provide technical information on the best chemicals and how best to utilize them. We have provided the industry with experimental data supporting the section 18 special emergency exemption registration for the use of the fungicides and provided the industry with data to support the EPA approval of new fungicides.

Publications

Qu, Xinshun, L. A. Wanner, and B. J. Christ. 2008. Using the TxtAB Operon to Quantify Pathogenic Streptomyces in Potato Tubers and Soil. Phytopathology 98: 405-412.

Burkhart, C. R., B. J. Christ and K. G. Haynes. 2007. Non-additive genetic variance governs resistance to Fusarium dry rot in a diploid hybrid potato population. Amer. J. Potato Res. 84: 199-204.

Haynes, K. G., R. W. Goth, D. H. Lambert and B. J. Christ. 2007. Evaluation of a short-day adapted tetraploid potato population with horizontal resistance to Phytophthora infestans under long-day conditions in Northern Maine. Amer. J. Potato Res. 84:459-466.

Qu, Xinshun and B. J. Christ. 2007. In vitro culture of the obligate parasite Spongospora subterranea (Cercozoa; Plasmodiophorida) associated with root-inducing transferred-DNA transformed potato hairy roots. J. Eukarot. Microbiol. 54:465-467.

De Jong, W. S., D. E. Halseth, B. B. Bodie, K. L. Perry, J. B. Sieczka, B. J. Christ, G. A. Porter, K. M. Paddock, M. W. Peck and R. L. Plaisted. 2006. Marcy: A chipping variety with resistance to common scab. Amer. J. Potato Res. 83:189-193.

Haynes, K. G. and B. J. Christ. 2006. Recurrent Maternal Half-Sib Selection Improves Foliar Late Blight Resistance in a Diploid Hybrid Solanum phureja – S. stenotomum Population. Amer. J. Potato Res. 83:181-188.

Qu, Xinshun and B. J. Christ. 2006. Host range of Spongospora subterranea f. sp. subterranea in the United States. Amer J. Potato Res. 83:334-347.

Qu, X. and B. J. Christ. 2006. Single cystosorus isolate production and restriction fragment length polymorphism characterization of the obligate biotroph Spongospora subterranea f. sp. subterranea. Phytopathology 96:1157-1163.

Qu, X, J. A. Kavanagh, D. Egan and B. J. Christ. 2006. Detection and quantification of Spongospora subterranea f. sp. subterranea by PCR in host tissue and naturally infested soils. Amer. J Potato Res. 83:21-30.

Simko, I. S. Cosatnzo, V. Ramanjulu, B. J. Christ and K. G. Haynes. 2006. Mapping polygenes for tuber resistance to late blight in a diploid Solanum phureja X S. stenotomum hybrid population. Plant Breeding 125:385-389.

Valluru, R., B. J. Christ, K. G. Haynes and B. T. Vinyard. 2006. Inheritance and stability of resistance to Fusarium tuber rot in tetraploid potatoes. Amer. J. Potato Res. 83:335-341.

Costanzo, S, I. Simko, B. J. Christ and K. G. Haynes. 2005. QTL analysis of late blight resistance in a diploid potato family of Solanum phureja x S. stenotomum. Theor. Appl. Genet. 111:609-617.

Shuman, J. L. and B. J. Christ. 2005. Incorporation of a host resistance factor into the FAST system to forecast early blight of potatoes. Amer. J. Potato Res. 82:9-19.

Costanzo, S, B. J. Christ and K. G. Haynes. 2004. Late blight resistance in a diploid full-sib potato family. Plant Breeding 123:377-381.

Overton, B. E., E. L. Stewart, X. Qu, N. G. Wenner and B. J. Christ. 2004. Qualitative real-time PCR SYBR Green detection of Petri disease fungi. Phytopathol. Mediterr. 43:403-410.

Qu, Xinshun and B. J. Christ. 2004. Genetic variation and phylogeny of Spongospora subterranea f. sp. subterranea based on ribosomal DNA sequence analysis. Amer. J. Potato Res. 81:385-394.

Simko I, S. Costanzo, K.G. Haynes, B.J. Christ, and R.W. Jones. 2004. Linkage disequilibrium mapping of a Verticillium dahliae resistance quantitative trait locus in tetraploid potato (Solanum tuberosum) through a candidate gene approach. Theor. Appl. Genet. 108:217-224.

Simko I, S. K. G. Haynes, E. E. Ewing, Costanzo, B.J. Christ, and R.W. Jones. 2004. Mapping genes for resistance to Verticillium albo-atrum in tetraploid and diploid potato populations using haplotype association tests and genetic linkage analysis. Molecular Gen Genomics 271:522-531.

Simko, I. S. Costanzo, K. G. Haynes, B. J. Christ and R. W. Jones. 2003. "Identification of molecular markers linked to the Verticillium wilt resistance gene homologue in potato (Solanum tuberosum L.)." Acta Hort.

Christ, B. J., K. G. Haynes and B. T. Vinyard. 2002. "Inheritance of early blight resistance from an open-pollinated 4x-2x early blight resistant potatoes." Amer. J. Potato Res. 79: 403-410.

Haynes, K. G., B. J. Christ, D. P. Weingartner, D. S. Douches, C. A. Thill, G. Secor, W. E. Fry and D. H. Lambert. 2002. "Foliar resistance to late blight in potato clones evaluated in national trials in 1997." Amer. J. Potato Res. 79:451-457.

Christ, B. J. and K. G. Haynes. 2001. "Inheritance of resistance to early blight disease in a diploid potato population." Plant Breeding 120:169-172.

Haynes, K. G., G. A. Porter, B. J. Christ, R. W. Goth, K. O. DeLong, D. E. Halseth, J. B. Sieczka, M. R. Henninger, S. B. Sterrett, G. C. Yencho, and R. E. Webb. 2001. "Amey: A multi-purpose, russet skinned cultivar for specialty markets." Amer. J. Potato Res. 78:175-181.

Plaisted, R. L., D. E. Halseth, B. B. Brodie, S. A. Slack, J. B. Sieczka, B. J. Christ, K. D. Paddock, and M. W. Peck. 2001. "Eva: A midseason golden nematode and virus resistant variety for use as tablestock or chipstock." Amer. J. Potato Res. 78:65-68.

Foolad, M. R., N. Ntahimpera, B. J. Christ, and G. Y. Lin. 2000." Comparison between field, greenhouse and detached leaflet evaluations of tomato germplasm for early blight resistance." Plant Disease 84:967-972.

Haynes, K. G. and B. J. Christ. 1999. "Heritability of resistance to foliar late blight in a diploid hybrid potato population of Solanum phureja xS. stenotomum." Plant Breeding 118:431-434.

Plaisted, R. L., D. E. Halseth, B. B. Brodie, S. A. Slack, J. B. Sieczka, B. J. Christ, K. D. Paddock, and M. W. Peck. 1998. "Pike: A full season scab and nematode resistant chipstock variety." Amer.J. Potato Research 75:117-120.

Plaisted, R. L., D. E. Halseth, B. B. Brodie, S. A. Slack, J. B. Sieczka, B. J. Christ, K. D. Paddock, and M. W. Peck. 1999. "Reba: A mid to late season golden nematode resistance variety for use as tablestock or chipstock." Amer. J. Potato Res. 76: 1-4.

Haynes, K. G., D. H. Lambert, B. J. Christ, D. P. Weingartner, D. S. Douches, J. E. Backlund, G. Secor, W.Fry, and W. Stevenson. 1998." Phenotypic stability of resistance to late blight in potato clones evaluated at eight sites in the United States." Amer. J. Potato Research 75: 211-217.

Plaisted, R. L., D. E. Halseth, B. B. Brodie, S. A. Slack, J. B. Sieczka, B. J. Christ, K. D. Paddock, and M. W. Peck. 1998. "Andover: An early to midseason golden nematode resistant variety for use as chipstock or tablestock." Amer. J. Potato Research 75:113-116.

Weir, T., D. R. Huff, B. J. Christ, and C. P. Romaine. 1998. "RAPD-PCR Analysis of genetic variation in populations of Alternaria solani and Alternaria alternata from potato and tomato." Mycologia 90: 813-821.