Source: CORNELL UNIVERSITY submitted to
BIO-BASED MANAGEMENT AND MICROBIAL MECHANISMS OF APPLE REPLANT DISEASE
 
PROJECT DIRECTOR: Merwin, I. A. Thies, J. E. Fazio, G. Nelson, E. B.
 
PERFORMING ORGANIZATION
HORTICULTURE
CORNELL UNIVERSITY
ITHACA,NY 14853
 
NON TECHNICAL SUMMARY: Soilborne pathogens often attack the roots of newly planted apple trees in old orchard sites. Biobased alternatives are needed to control this apple replant problem. We are testing new apple rootstocks that may be resistant or tolerant to apple replant problems, and investigating the role of rhizosphere microbial community composition in replant disease resistance.
 
OBJECTIVES: The objectives of this research are: 1) To evaluate apple replant disease (ARD) resistance or tolerance among different clonal rootstocks; 2) To test the efficacy and economics of various preplant soil treatments and tree-planting practices for replant disease control in orchards; 3) To test the resistance to soil-borne root pathogens in ten new and two commonly used apple rootstock clones; 4) To investigate possible mechanisms for rootstock disease resistance or tolerance by studying the differences and changes over time in soil microbial community structure in the rhizosphere of different apple rootstocks in various orchard soils mixtures and preplant soil treatments; and 5) To provide practical information and strategies for biologically-based management of ARD without the need for soil fumigation.
 
APPROACH: Orchard replant disease is a complex of soil-borne diseases that cause severe stunting of newly planted trees, decreased yields, and economic losses in many regions when growers attempt to renovate and replant old orchard sites. Methyl bromide has been the most effective soil treatment to control this problem, but it must now be replaced by safer soil fumigants or biologically based methods for replant disease management. New York ranks second nationally in apple production, and apple replant disease (ARD) is a serious problem in about half of NY orchards. Two years ago we began an experiment testing disease-resistant rootstocks, preplant compost amendments, and soil fumigation with Telone C-17 (a possible substitute for methyl bromide) in an old orchard site with a history of ARD. We also used molecular fingerprinting techniques to study the effects of soil fumigation, rootstock genotypes, and compost on ARD symptoms and soil microbial communities in and around the roots of newly planted apple trees. We found that two new Cornell-Geneva (CG) rootstocks (CG30 and CG210) were more resistant to ARD than conventional rootstocks. Neither compost nor fumigation with Telone C-17 worked as well as these two disease-resistant rootstocks for promoting healthy tree and root growth in this orchard. We also observed that soil microbial communities were substantially different around the roots of disease resistant vs. disease susceptible rootstocks, and in old tree rows vs. grass lanes. To follow up on these interesting results, we need to continue this replant experiment for three more years, to obtain yield data and determine the long-term efficacy and cost/benefit relationships of alternative ARD control strategies. To investigate further the extent of ARD resistance in other new rootstocks of the CG series, in April 2003 we began a test planting of 360 rootstocks, representing 10 new CG rootstock genotypes and two standard (Malling) rootstocks for comparison. We planted these rootstocks into 20-L pots containing three mixtures of soil from orchards in each of NY states three main fruit-growing regions. Half of each soil mixture was steam pasteurized, and the other half left untreated. Comparing the growth and physiological functions of these rootstocks in pasteurized vs. untreated soils mixtures during the next three years will enable us to evaluate each rootstocks resistance to the ARD complex prevalent in NY orchards. Our studies of rhizosphere microbial diversity will be combined with studies of genetic diversity of rootstocks that are the main focus of the research of co-PI Dr. Fazio. The collective results of these proposed studies will give new insights into possible mechanisms of ARD resistance, tolerance, or suppression. This could provide some practical, biologically based strategies for fruit growers to manage orchard replant problems without methyl bromide.
 
CRIS NUMBER: 0201052 SUBFILE: CRIS
PROJECT NUMBER: NYC-145560 SPONSOR AGENCY: CSREES
PROJECT TYPE: OTHER GRANTS PROJECT STATUS: TERMINATED MULTI-STATE PROJECT NUMBER: (N/A)
START DATE: Aug 1, 2004 TERMINATION DATE: Jan 31, 2008

GRANT PROGRAM: IP-METHYL BROMIDE
GRANT PROGRAM AREA: Integrated Programs

CLASSIFICATION
Knowledge Area (KA)Subject (S)Science (F)Objective (G)Percent
205111010602.225%
212111010604.225%
215111010604.225%
216111010604.225%

CLASSIFICATION HEADINGS
KA212 - Pathogens and Nematodes Affecting Plants
KA215 - Biological Control of Pests Affecting Plants
KA216 - Integrated Pest Management Systems
KA205 - Plant Management Systems
S1110 - Apple
F1060 - Biology (whole systems)
G2.2 - Increase Efficiency of Production and Marketing Systems
G4.2 - Reduce Number and Severity of Pest and Disease Outbreaks


RESEARCH EFFORT CATEGORIES
BASIC 25%
APPLIED 75%
DEVELOPMENTAL (N/A)%

KEYWORDS: fumigation; rhizosphere; microbial ecology; dna fingerprinting; malus pumila; apples; orchards; replant disease (apples); tree diseases; rootstocks; composts; tree genetics; plant disease resistance; mechanisms; biological control (diseases); integrated pest management; soil treatment; soil borne diseases; soil microbiology; soil microorganisms; pre planting

PROGRESS: Aug 1, 2004 TO Jan 31, 2008
OUTPUTS: The objectives of this project were to improve understanding and control of apple replant disease (ARD), providing sustainable alternatives to the use of methyl bromide or other broad-spectrum soil fumigants. Field experiments began in 2001 at a site in Ithaca NY, where apple had been grown for the past 80 years, and the previous orchard showed many symptoms of ARD. We evaluated combinations of five clonal rootstocks, two planting positions, and four pre-plant ARD soil treatments: 1) soil fumigation with Telone C-17 (1,3-dichloropropene plus chloropicrin); 2) soil amendments with compost; 3) a combination of compost plus fumigation; and 4) non-treated control plots. Empire apple trees grafted on G30, CG6210, G16, M7, and M26 rootstocks were planted into plots previously treated as above, situated either in the previous tree rows or in previous grass drive lanes of the prior orchard at this site. After 6 years, trees continued to grow and yield more on CG.6210 and G.30 compared with all other rootstocks, and this response was correlated with increased root growth and survival. PCR-DGGE and TRFLP DNA fingerprints showed that soil microbial populations associated with ARD rebounded within a few years of preplant soil treatments, but remained distinct among various rootstock clones. An experiment involving reciprocal plantings of different rootstock clones showed that ARD severity was affected by the previous rootstock clones or series (i.e. Malling vs. Cornell-Geneva rootstocks), and was consistently reduced following CG6210. Another study demonstrated that ARD was more severe in tree rows of four different groundcover management systems, compared to soil from the adjacent grass drive lanes. Soil microbial communities, and soil nutrient availability differed among all four GMSs compared with the drive lanes. There was no direct correlation among apple bioassay seedling growth or ARD symptoms, and soil microbial composition as assessed with T-RFLP and DGGE followed by gene sequencing and GENBANK searches that identified certain microbial phylla as characteristic of each GMS. Soil respiration, populations of culturable bacteria and fungi, and soil nutrient availability were not reliable predictors of either apple bioassay or cumulative apple tree growth and yields among the different GMSs or rootstocks. This project showed that resistant or tolerant apple rootstocks can provide a reliable and sustainable method for managing ARD in orchards without soil fumigation, and that previous GMSs maintained in the tree rows also influence the symptoms and severity of ARD in successive plantings. PARTICIPANTS: Aside from the listed PIs for this project, it involved a post-doctoral fellow for the past three years (Dr. Angelika Rumberger), two Cornell University graduate students (Dr. Shengrui Yao and Michelle Leinfelder),and a commercial orchard in Ithaca NY. TARGET AUDIENCES: The target audiences for this project are tree-fruit growers throughout the US, and elsewhere in the world fruit industry, where replant disease is a significant problem.

IMPACT: 2004-08-01 TO 2008-01-31 We found that some new apple rootstocks are substantially more tolerant than the most-used conventional rootstocks to soil-borne diseases that often stunt fruit-tree establishment and reduce yields in apple replant situations throughout North America and Europe. We also observed that rootstock genotypes and tree-row groundcover management systems can influence strongly the microbial communities in the soil around fruit-tree roots. The symptoms of apple replant disease were reduced even for conventional rootstocks when other disease-resistant rootstocks such as CG6210 were previously grown in orchard soils. These outcomes could help tree-fruit growers to renovate their orchards more quickly and profitably, using non-chemical methods that do not harm the environment and are safe for farm families and workers. They also demonstrate the potential economic and environmental benefits that could result from increased breeding and selection of disease-resistant rootstocks for tree crops.

PUBLICATION INFORMATION: 2004-08-01 TO 2008-01-31
St.Laurant, A., I.A. Merwin and J.E. Thies. 2008. Long-term orchard groundcover management systems affect soil microbial communities and apple replant disease severity. Plant and Soil. (In press).

PROJECT CONTACT INFORMATION
NAME: Decker, D. J.
PHONE: 607-255-2224
FAX: 607-255-9499