Articles
Horticultural field performance of new putative disease resistant walnut rootstock genotypes compared to standard clonal and seedling Paradox rootstocks
Article number
1420_3
Pages
17 – 24
Language
English
Abstract
Most commercial walnuts in California are produced on either seedling or clonal hybrid Paradox rootstocks.
Seedling Paradox is susceptible to the soilborne pathogens Agrobacterium tumefaciens (cause of crown gall disease) and Phytophthora species (crown and root rots), while commercially available clonal Paradox rootstocks have varying degrees of resistance.
We have identified new rootstock genotypes that exhibit elevated levels of resistance to these pathogens and parasitic nematodes.
Here we report on the performance of four of these novel rootstocks in four orchard trials where they were exposed to differing soil and disease challenges in California’s walnut-growing regions. ‘Chandler’ was budded onto four experimental hybrid rootstock genotypes, ‘11-991’, ‘K3’, ‘29JM 8’, ‘STJM4’, with putative resistance to Agrobacterium or Phytophthora. These bare root June budded trees were planted in 2016 at the four locations.
The trials included commercially available clonal ‘VX211’, ‘RX1’, and ‘Vlach’, and seedling Paradox rootstocks.
Rootstock performance was assessed by examining incidence of tree mortality, rootstock and scion growth, canopy light interception, yield, and nut quality.
Tree mortality, mainly resulting from failure to establish rather than from disease, was lowest on commercially available (standard) clonal rootstocks and experimental rootstock ‘11-991’. Scion growth was greatest on trees on the three standard clones, while there were no significant growth differences between scions on seedling Paradox and the new genotypes when data from all trial sites were combined. ‘Chandler’ on ‘Vlach’ yielded well at each site, while ‘Chandler’ on seedling Paradox had the lowest yields at three trial sites. ‘Chandler’ on experimental rootstock ‘K3’ had equivalent yields to the standard ‘VX211’ at three trial sites.
Seedling Paradox had the lowest scion uniformity and exhibited significantly more crown gall than any of the commercial or experimental clonal rootstocks.
Our results indicated that several experimental rootstocks examined here are horticulturally similar to the commercially available clonal rootstocks and may represent commercially viable options for the industry.
Seedling Paradox is susceptible to the soilborne pathogens Agrobacterium tumefaciens (cause of crown gall disease) and Phytophthora species (crown and root rots), while commercially available clonal Paradox rootstocks have varying degrees of resistance.
We have identified new rootstock genotypes that exhibit elevated levels of resistance to these pathogens and parasitic nematodes.
Here we report on the performance of four of these novel rootstocks in four orchard trials where they were exposed to differing soil and disease challenges in California’s walnut-growing regions. ‘Chandler’ was budded onto four experimental hybrid rootstock genotypes, ‘11-991’, ‘K3’, ‘29JM 8’, ‘STJM4’, with putative resistance to Agrobacterium or Phytophthora. These bare root June budded trees were planted in 2016 at the four locations.
The trials included commercially available clonal ‘VX211’, ‘RX1’, and ‘Vlach’, and seedling Paradox rootstocks.
Rootstock performance was assessed by examining incidence of tree mortality, rootstock and scion growth, canopy light interception, yield, and nut quality.
Tree mortality, mainly resulting from failure to establish rather than from disease, was lowest on commercially available (standard) clonal rootstocks and experimental rootstock ‘11-991’. Scion growth was greatest on trees on the three standard clones, while there were no significant growth differences between scions on seedling Paradox and the new genotypes when data from all trial sites were combined. ‘Chandler’ on ‘Vlach’ yielded well at each site, while ‘Chandler’ on seedling Paradox had the lowest yields at three trial sites. ‘Chandler’ on experimental rootstock ‘K3’ had equivalent yields to the standard ‘VX211’ at three trial sites.
Seedling Paradox had the lowest scion uniformity and exhibited significantly more crown gall than any of the commercial or experimental clonal rootstocks.
Our results indicated that several experimental rootstocks examined here are horticulturally similar to the commercially available clonal rootstocks and may represent commercially viable options for the industry.
Publication
Authors
J. Hasey, L. Milliron, E. Fichtner, R. Elkins, B. Lampinen, C. Reyes, D. Lightle, C. Leslie, A. McClean, G. Browne, D. Kluepfel
Keywords
‘Chandler’ horticultural rootstock performance, hybrid Paradox rootstocks, ‘VX211’, ‘RX1’, ‘Vlach’, ‘11-991’, ‘K3’, ‘29JM 8’, ‘STJM4’
Groups involved
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