Plant and Soil

, Volume 304, Issue 1, pp 209–225

Long-term orchard groundcover management systems affect soil microbial communities and apple replant disease severity

  • Angelika St. Laurent
  • Ian A. Merwin
  • Janice E. Thies
Regular Article

DOI: 10.1007/s11104-008-9541-4

Cite this article as:
St. Laurent, A., Merwin, I.A. & Thies, J.E. Plant Soil (2008) 304: 209. doi:10.1007/s11104-008-9541-4

Abstract

Apple replant disease (ARD) is a soil-disease syndrome of complex etiology that affects apple tree roots in replanted orchards, resulting in stunted tree growth and reduced yields. To investigate whether different groundcover management systems (GMSs) influence subsequent ARD severity, we grew apple seedlings in an outdoor nursery in pots containing orchard soil from field plots where four GMSs had been maintained for 14 years in an orchard near Ithaca, NY, USA. The GMS treatments were: (1) pre-emergence herbicide (Pre-H), bare soil strips maintained by applying tank-mixed glyphosate, norflurazon and diuron herbicides annually; (2) post-emergence herbicide (Post-H), sparse weed cover maintained by applying glyphosate in May and July each year; (3) mowed sod grass (Mowed Sod); and (4) bark mulch (Mulch). Soils were also sampled from the grass drive lane maintained between the trees in the orchard (Grass Lane). Sampled soils (Orchard soil) were either pasteurized or left untreated, placed into 4-L pots, and planted with one apple seedling per pot. After 3 months of growth, soil (Bioassay soil) and apple tree roots (Bioassay roots) were sampled from each pot and microbial populations colonizing samples were characterized. Seedling growth was reduced in soils sampled from all four GMS treatments compared to the Grass Lane soils. Among the GMS treatments, seedling biomass was greater in Pre-H than in the Post-H soil. Soil microbial communities and nutrient availability differed among all four GMS treatments and the Grass Lane. Root-lesion (Pratylenchus sp.) nematode populations were higher in the Mowed Sod than in the other GMS treatments. Soil bacterial and fungal community composition was assessed in Orchard and Bioassay soils and Bioassay roots with a DNA fingerprinting method (T-RFLP). Redundancy analysis indicated that soils sampled from the different GMS treatments differentially influenced seedling biomass. A clone library of 267 soil bacteria was developed from sampled Orchard soils and Bioassay roots. These communities were dominated by Acidobacteria (25% of sequences), Actinobacteria (19%), δ-Proteobacteria (12%), β-Proteobacteria (10%), and these ratios differed among the GMS soils. Members of the family Comamonadaceae were detected only in tree-row soil, not in the Grass Lanes. The dominant sequences among 145 cloned fungi associated with apple seedling roots were Fusarium oxysporum (16% of sequences), an uncultured soil fungus submitted under DQ420986 (12%), and Rhodotorula mucilaginosa (9%). In a redundancy analysis, factors including fungal and oomycete community compositions, soil respiration rates, population sizes of culturable bacteria and fungi, soil organic matter content, and nutrient availability, were not significant predictors of apple seedling biomass in these soils. Different GMS treatments used by apple growers may influence subsequent ARD severity in replanted trees, but edaphic factors commonly associated with soil fertility may not reliably predict tree-root health and successful establishment of replanted orchards.

Keywords

Apple replant diseaseGlyphosateNorflurazonDiuronHerbicidesMulchOrchard floor managementSoil microbial communities

Abbreviations

AMMI

Additive Main effects with Multiplicative Interaction

ARD

Apple Replant Disease

DGGE

Denaturing Gradient Gel Electrophoresis

GMS

Groundcover Management Systems

ITS

Internal Transcribed Spacer

OTU

Operational Taxonomic Unit

PCA

Principal Component Analysis

RDA

Redundancy Analysis

T-RFLP

Terminal Restriction Fragment Length Polymorphism

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Angelika St. Laurent
    • 1
  • Ian A. Merwin
    • 2
  • Janice E. Thies
    • 1
  1. 1.Department of Crop and Soil ScienceCornell UniversityIthacaUSA
  2. 2.Department of HorticultureCornell UniversityIthacaUSA