Investigations into peach seedling stunting caused by a replant soil

Abstract

Replant diseases often occur when pome and stone fruits are grown in soil that had previously been planted with the same or similar plant species. They typically lead to reductions in plant growth, crop yield and production duration. In this project, greenhouse assays were used to identify a peach orchard soil that caused replant disease symptoms. Biocidal treatments of this soil led to growth increases of Nemaguard peach seedlings. In addition, plants grown in as little as 1% of the replant soil exhibited reduced plant growth. These results suggest that the disease etiology has a biological component. Analysis of roots from plants exhibiting various levels of replant disease symptoms showed little difference in the amounts of PCR-amplified bacterial or fungal rRNA genes. However, analysis using a stramenopile-selective PCR assay showed that rRNA genes from this taxon were generally more abundant in plants with the smallest top weights. Nucleotide sequence analysis of these genes identified several phylotypes belonging to Bacillariophyta, Chrysophyceae, Eustigmatophyceae, Labyrinthulida, Oomycetes, Phaeophyceae and Synurophyceae. Sequence-selective quantitative PCR assays targeting four of the most abundant phylotypes showed that both diatoms (Sellaphora spp.) and an oomycete (Pythium ultimum) were negatively associated with plant top weights.

Managing the almond and stone fruit replant disease complex with less soil fumigant

“…Several rootstocks for almonds and stone fruit have shown genetic resistance to root knot nematodes, but little resistance has been demonstrated against the other two major nematode pests affecting these crops, the ring nematode and the root lesion nematode (McKenry 2007). PRD, which is much more widespread than nematode damage on almonds and stone fruits, is a poorly understood soilborne disease complex that suppresses early growth and cumulative yield in replanted almond and peach orchards (Bent et al 2009;Browne et al 2006). It afflicts successive generations of almonds and stone fruit planted at the same location and is associated with poor health of the trees' fine roots and incidence of several plantparasitic fungi and oomycetes.…”

“…Research has documented myriad problems that can suppress growth and productivity in such replanted orchards (Bent et al 2009;Browne et al 2006;Larsen 1995;McKenry 1996McKenry , 1999Westerdahl and McKenry 2002). Abiotic soil factors related to previous crop production, such as compaction, salinity, suboptimal pH, nutritional imbalances and herbicide residues, can compromise the performance of replanted orchards, but many of these problems can be avoided or remedied without great difficulty or expense.…”

Productive and vegetative performance of peach trees grafted on six rootstocks in a replanting area

“…Replant diseases are common in many regions of the world, occurring when stone fruit are planted on soils that have been previously cultivated with similar species (Bent et al, 2009). The causes of replant diseases are still unknown, although many factors appear to be involved.…”

“…2016 DOI: 10.1590/S0100-204X2016000400009 of root tissue from previous crops, which generates hydrocyanic acid, a phytotoxic compound associated with replant diseases (Gur & Cohen, 1989;Benizri et al, 2005). In plants, the most characteristic effects of replant diseases are the reduction of vigor and yield, besides the orchard's low longevity (Rutto & Mizutani, 2006;Bent et al, 2009). Soil fumigation with chemical compounds has been used as a control technique, resulting in an increase in plant growth and yield, but it still presents low efficiency levels, high implementation costs, and a risk to human health and to the environment (Leinfelder & Merwin, 2006).…”

Characterization of species associated with Pythium soft rot of ginger and evaluation of Pythium Oligandrum as a biocontrol

“…By monitoring either directly amplified PCR products bound with a fluorescent dye or complementary probe, or indirectly generated fluorescence applying the exonuclease activity of Taq polymerase, proportions of the PCR products or fluorescence could be determined directly (Okubara et al, 2005 Kernaghan et al (2008) also fully amplified ITS regions of P. ultimum and P. irregulare group I and IV in American ginseng field soil samples by using specifically designed primers. Additionally, qPCR was implemented to identify and quantify P. vexans based on the small subunit (SSU) and ITS region of the genome (Bent et al, 2009;Spies et al, 2011b). There are more than 20 different primer sets working specifically on a broad range of Pythium spp.…”