Performing Department
Genetics and Biochemistry
Non Technical Summary
The goal of our research is the development of an integrated disease management strategy for Peach Tree Short Life PTSL and Armillaria root rot of peach trees in the southeastern U.S. employing biomarkers to monitor the progression of these diseases and to select for improved performance of rootstocks in disease prevalent regions. Toward this goal, we propose the following aims: 1) Continue to evaluate F3 selections of Guardian Brand BY520-9 as rootstocks on Peach Tree Short Life (PTSL) sites in South Carolina for survival and productivity. 2) Utilizing the molecular mapping data from crosses segregating for tolerance ring nematode/PSTL, test molecular marker alleles in the critical QTL regions for prediction of PSTL tolerance in BY520-9 selections still under field-testing, and verify the utility of these markers as predictors of disease. 3) Utilizing the peach genomic resources, further dissect the critical QTL intervals for more robust markers for use in MAS of ring nematode /PSTL tolerance. Integrate molecular markers into MAS approaches for breeding tolerant rootstocks. 4) Utilizing the available genomic resources for peach (whole genome sequences) search for specific gene activities associated with pathogen attack, winter cold injury, and other PSTL/ Armillaria associated tree stresses as biomarkers for progression of the diseases. 5) Test specific treatment regimes for studying the process of Armillaria infection and establish a trial protocol to screen for potential biomarkers for predicting the disease state. The outcome of this research will be an environmentally friendly, integrated PTSL/ Armillaria management systems that will successfully control these diseases.
Animal Health Component
(N/A)
Research Effort Categories
Basic
50%
Applied
25%
Developmental
25%
Goals / Objectives
The disease syndrome of peach, nectarine, and plum trees in the southeastern United States known as Peach Tree Short Life (PTSL) is characterized by sudden collapse of otherwise apparently healthy trees just before, during, or just after flowering. The problem, which affects more than 70% of the peach acreage in the southeastern U.S., may develop in very young orchards (as early as one year after planting), but the losses generally are most common and severe in trees four to seven years of age. In addition to PSTL, peach tree decline due to Armillaria root rot is a major problem not only in commercial stone fruit orchards of the southeastern United States but also on the west U.S. coastal regions and in the northeastern United States. Recommendations for disease management have not been developed because chemical, biological, or cultural control options are very limited and even fumigation practices cannot eradicate the disease. Commercially available rootstocks, including Guardian, are sensitive to this disease. The past and current situation in commercial peach orchards is that growers lose trees every year due to the consistent spread of the disease. The central goal of our research is the development of an integrated disease management strategy that manages PTSL and Armillaria root rot of peach trees in the southeastern U.S. through the utilization of biomarkers to monitor the progression of these diseases and to serve as tools to select for improved performance of rootstocks in disease prevalent regions. With this goal in mind, we propose the following specific aims: 1. Continue to evaluate F3 selections of Guardian Brand BY520-9 as rootstocks on Peach Tree Short Life (PTSL) sites in South Carolina for survival and productivity. 2. Utilizing the molecular mapping data from crosses segregating for tolerance ring nematode/PSTL, test molecular marker alleles in the critical QTL regions for prediction of PSTL tolerance in BY520-9 selections still under field-testing, and verify the utility of these markers as predictors of disease. 3. Continue the testing of new markers from the critical QTL intervals (derived from the peach genome sequences for use in MAS of ring nematode /PSTL tolerance. Integrate molecular markers into MAS approaches for breeding tolerant rootstocks. 4. Identify from marker association studies, above, candidate genes in the QTL regions whose activities are associated with pathogen attack, winter cold injury, and other PSTL/Armillaria associated tree stresses as biomarkers for progression of the disease. 5. Test specific treatment regimes for studying the process of Armillaria infection and establish a trial protocol to screen for potential biomarkers for predicting the disease state. The expected outputs of DNA markers for tolerance to PSTL and biomarkers for progression of the disease states of these important peach tree diseases will allow monitoring of rootstock germplasm breeding resources for improvement of resistance to these diseases in root stock varieties.
Project Methods
Aim 1: Guardian Brand BY520-9 has outperformed all other rootstocks in tree survival on severe PTSL sites in the southeastern U.S. However, there is an unacceptable amount of genetic variation in the seedling population of this seed derived rootstock. This is attributed to the fact that the original BY520-9 tree was destroyed. Therefore, the open-pollinated F1 genotypes from BY520-9 in the 1983 tests and their subsequent controlled cross F1 and F2 progenies need to be evaluated as potential seed orchard parents. We will employ standard field evaluations to identify trees that have robust tolerance to PSTL. This will include, evaluation of rootstock materials of Guardian, and progeny of crosses with Guardian and susceptible rootstocks. AIM 2: Guardian selections and their superior F1 genotypes and F2 trees from the cross 3-17-7 X Nemaguard that segregates for PTSL tolerance will continue to be examined for allelic composition of the markers that are in QTL regions from our previous work. Additional F2 trees that succumb to PSTL in this year will be added to our mapping work to further define the markers that correlate with susceptibility or tolerance to PTSL. AIM 3: We are mining the genome sequence of peach for sequences that span QTL regions in peach. We are developing markers from the sequences that surround these putative PSTL markers. We are testing these additional markers currently. Markers that are reproducible will be used for further analysis of Guardian rootstock selections in future years and tested in MAS for improved tolerance to PSTL. AIM 4: We have available from our work both in mapping PSTL tolerance QTLs and work on genes controlling winter chill and dormancy phenomena genes that could potentially serve as biomarkers for progression of the disease. We will examine the levels of expression by RT-PCR of a number of dormancy and chilling requirement candidate genes in our PSTL tolerant segregating families. Aim 5: With Amillaria infection, our goal components include (i) the development of a simple, fast, and reliable pathogenicity assay to accelerate selection for ARR-tolerant rootstocks and in the future help to identify biomarkers that predict the early progress in the disease state; (ii) the development of transgenic, ARR-tolerant rootstocks, (iii) novel ways to grow trees while suppressing the progress of the pathogen in infected trees. For this, we will 1) Establish a field trial and laboratory approaches for rootstock susceptibility tests against Armillaria root rot of peach that could be used to screen for potential biomarkers for the disease state. 2) Screen 20 new BlueByrd plum lines expressing gafp-1 under the control of a novel root-specific promoter for root rot resistance under controlled conditions. 3) Establish and maintain field trials to investigate horticultural, chemical, and biotechnological management options for Armillaria root rot control.