2010 Annual Report
1a.Objectives (from AD-416)
Develop improved nematode management strategies based on cultural and biocontrol approaches for suppression of ring and (or) root-knot nematode and related peach disease complexes and elucidate the interactive effects and (or) incidence among key nematode pests, pathogenic fungi, and rootstocks to improve the understanding of host susceptibility associated with peach and pecan tree decline problems, such as Peach Tree Decline and Pecan Replant Disease.
1b.Approach (from AD-416)
Evaluate selected rotation crop for suppression of root-knot nematode as an alternative to fumigation; investigate natural products associated with rotation crop for effect on nematode egg hatch and vermiform-life stage survival; investigate solarization alone and in combination with the application of a cocktail of biocontrol agents for nematode management when delivered through irrigation; characterize the suppressive effects of biocontrol agent towards the Pecan and Peach root-knot nematodes; develop new knowledge regarding interactive effects among nematode pests and (or) pathogenic fungi as associated with peach and (or) pecan replant disease; and evaluate advanced Prunus germplasm for resistance to continuous root-knot nematode pressure under field conditions.
Resources will support research already taking place on this project. This includes development of strategies or approaches to minimize the economic impact of nematodes and other pathogens on peach and pecan. Work involves ground covers, alternatives to chemical nematicides, and biological agents to reduce nematode populations in soils.
The research outlined in this project contributes to the overall mission of ARS to develop new technology and knowledge in order to solve deciduous tree fruit and nut problems of high national priority. This research addresses selected rotation crops, the use of bacteria biocontrol agents, the evaluation of advanced rootstock selections in microplots, and evaluation of interactions between nematodes and (or) Armillaria root rot fungus that will result in advanced knowledge and improved pre- and postplant nematode management recommendations and tree survival on PTSL or replant sites.
In Fiscal Year (FY) 2010:.
1)One and two-year preplant crop rotations, preplant fumigation, and unfumigated treatment plots were replanted with Rubyprince on Halford rootstock to study the suppression of nematode infestation, thus promoting tree growth on a root-knot nematode infested field site. Nematode population densities and tree growth data were determined in respective plots;.
2)Crude root exudate from rotation grass has been challenged against root-knot nematode second-stage juveniles (J2) and eggs under laboratory conditions. Preliminary results indicate that egg hatch and J2 mobility are suppressed by root exudate. Experiments evaluating grass against three other root-knot nematode species under greenhouse conditions at ARS-Byron and ARS-Beltsville locations have been completed. Results indicate that not all nematode species are suppressed by this grass. Plan to determine why grass suppresses specific root-knot nematode species;.
3)The effect of soil solarization alone and in combination with the cocktail of biocontrol agents on suppression of ring nematode and tree mortality continues. Nematode population dynamics, tree growth, and PTSL tree death data recorded. Winter wheat planted in respective plots. Preplant soil solarization appears to be as good as preplant methyl bromide in promoting tree survival on a PTSL site;.
4)Field microplot experiment to study best P. penetrans isolate for biocontrol of the pecan root-knot nematode was initiated at ARS-Byron location. Treatments included i) nematode-alone, ii) biocontrol agent-alone, iii) nematode + biocontrol agent, and iv) control. All microplots planted to Elliott pecan seedlings. Results inconclusive at this time;.
5)Tree growth & symptomatology data recorded as related to Armillaria root rot fungus + nematode interaction field microplot study. Preliminary results indicate that percentage of tree death is greater when both nematodes + fungus occur together than alone or absent; and.
7)Nematode population dynamics, peach tree growth & symptomatology data recorded among rootstock treatments with and without continuous root-knot nematode pressure in field microplots. Nematode soil populations are remaining greatest under Lovell vs. Guardian rootstock and regardless of continuous weed presence. Fruit yield data will be recorded for 2nd time in FY-2010.
Interaction between lesion and root-knot nematodes in peach. A 26-month long field study was conducted at ARS Byron, GA to determine the interaction between the root-knot and lesion nematodes as related to peach tree growth. Results indicate that the root-knot nematode suppressed tree growth in peach more than lesion nematode. These data provide useful insights into the need for developing appropriate root-knot nematode management strategies in peach.
Nyczepir, A.P., Thomas, S.H. 2009. Current and future management strategies in intensive crop production systems. In: Perry, R.N., Moens, M., Starr, J.L. editors. Root-Knot Nematodes. Wallingford, Oxfordshire, UK:CABI. p. 412-443.
Nyczepir, A.P., Nagel, A.K., Schnabel, G. 2009. Host status of three transgenic plum lines to Mesocriconema xenoplax. HortScience. 44(7):1932-1935.
Nyczepir, A.P. 2009. Dynamics of concomitant populations of Pratylenchus vulnus and Meloidogyne incognita on peach. Nematropica. 39:373-279.