Articles
Identifying walnut (Juglans spp.) rootstocks with resistance and tolerance to plant-parasitic nematodes
Article number
1346_81
Pages
647 – 654
Language
English
Abstract
Walnut is an important nut tree crop in California.
About 85% of California walnut orchards are reported to be infested with root-lesion nematode, Pratylenchus vulnus. The commonly used rootstocks, Juglans hindsii × Juglans regia hybrids known as Paradox, are susceptible to this soil-dwelling parasite, particularly at planting.
For decades, P. vulnus was managed by pre-plant soil fumigation using methyl bromide or other nematicidal compounds.
Environmental and human health concerns call for alternative management options.
Host plant resistance and tolerance is an effective way to mitigate plant disease problems but identifying and utilizing resistant or tolerant accessions in walnut seedling populations have been challenging.
Using clonal propagation and in vitro embryo rescue techniques, it is now possible to clonally propagate walnut plants from interspecific crosses.
In this project, the response of P. vulnus to interspecific crosses of heterozygous parents of different Juglans species was tested.
Identifying walnut accessions resistant and tolerant to P. vulnus required measuring nematode populations for multiple years under field conditions.
A stepwise selection strategy identified walnut accessions superior to commercially available rootstocks.
These elite selections were then planted in regional rootstock trials and grafted to a common scion.
In these trials, the rootstock selections are exposed to field level soil-borne problems in non-treated and preplant fumigated plots.
Important horticultural traits and the durability of nematode resistance or tolerance were monitored and compared to the industry standard clonal rootstocks.
Multi-year field testing is expected to validate the P. vulnus resistance and tolerance identified in our selection process.
About 85% of California walnut orchards are reported to be infested with root-lesion nematode, Pratylenchus vulnus. The commonly used rootstocks, Juglans hindsii × Juglans regia hybrids known as Paradox, are susceptible to this soil-dwelling parasite, particularly at planting.
For decades, P. vulnus was managed by pre-plant soil fumigation using methyl bromide or other nematicidal compounds.
Environmental and human health concerns call for alternative management options.
Host plant resistance and tolerance is an effective way to mitigate plant disease problems but identifying and utilizing resistant or tolerant accessions in walnut seedling populations have been challenging.
Using clonal propagation and in vitro embryo rescue techniques, it is now possible to clonally propagate walnut plants from interspecific crosses.
In this project, the response of P. vulnus to interspecific crosses of heterozygous parents of different Juglans species was tested.
Identifying walnut accessions resistant and tolerant to P. vulnus required measuring nematode populations for multiple years under field conditions.
A stepwise selection strategy identified walnut accessions superior to commercially available rootstocks.
These elite selections were then planted in regional rootstock trials and grafted to a common scion.
In these trials, the rootstock selections are exposed to field level soil-borne problems in non-treated and preplant fumigated plots.
Important horticultural traits and the durability of nematode resistance or tolerance were monitored and compared to the industry standard clonal rootstocks.
Multi-year field testing is expected to validate the P. vulnus resistance and tolerance identified in our selection process.
Publication
Authors
A. Westphal, T.R. Buzo, Z.T.Z. Maung, M. McKenry, C.A. Leslie, P.J. Brown, D.A. Kluepfel
Keywords
rootstock breeding, Pratylenchus vulnus, graft compatibility, clonal propagation, Paradox walnut rootstock
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