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ARS Home » Pacific West Area » Davis, California » Crops Pathology and Genetics Research » Research » Publications at this Location » Publication #246925
Title: Resistance to phytophthora and graft compatibility with persian walnut among seedlings of chinese wingnut from different sources

Author
item Browne, Greg
item GRANT, JOE - University Of California
item Schmidt, Leigh
item LESLIE, CHARLES - University Of California
item MCGRANAHAN, GALE - University Of California

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2011
Publication Date: 3/1/2011
Citation: Browne, G.T., Grant, J.A., Schmidt, L.S., Leslie, C.A., Mcgranahan, G.H. 2011. Resistance to phytophthora and graft compatibility with persian walnut among seedlings of chinese wingnut from different sources. HortScience. 46:371-376.

Interpretive Summary: Seedlings from seven selections of Chinese wingnut (WN) representing collections of the USDA-ARS National Clonal Germplasm Repository at Davis CA and the University of California at Davis were evaluated as walnut rootstocks. They were tested for their resistance to Phytophthora cinnamomi and P. citricola and for their graft compatibility with important Persian walnut (Juglans regia) varieties. Seedlings of Northern California black walnut (NCB) (J. hindsii) and Paradox hybrid (PH) (typically J. hindsii × J. regia), which are used widely in commercial walnut orchards as standard rootstocks, were used in this research for comparisons with WN. All selections of WN seedlings were relatively resistant to P. cinnamomi and P. citricola (means of 0 to 36% of root and crown length rotted), compared to NCB (44 to 100%) and PH seedlings (11 to 100%). In 9-year graft compatibility trials in an orchard, NCB and PH rootstocks supported relatively good survival and growth of all tested walnut varieties (‘Chandler’, ‘Hartley’, ‘Serr’, ‘Tulare’, and ‘Vina’; mean scion survival 80 to 100%, mean scion circumference increase 442 to 630 mm), whereas results with WN were mixed. Wingnut rootstocks from all sources were incompatible with ‘Chandler’ (scion survival 20 to 60%, scion circumference increase 7 to 161 mm). Conversely, all WN rootstocks from all sources were compatible with ‘Tulare’ and ‘Vina’ (scion survival 80 to 100%, scion circumference increase 380 to 620 mm). Use of the WN rootstocks produced variable results in ‘Hartley’ and ‘Serr’ (mean scion survival 10 to 100%, mean scion circumference increase 0 to 554 mm). Among trees with surviving scions, rootstock sprouts were more prevalent on WN than on NCB or PH rootstocks. In a commercial walnut orchard infested with P. cinnamomi, ‘Hartley’ survived and grew markedly better on WN selections than on PH. It was concluded that WN selections may be useful in walnut rootstock breeding efforts. Also, in soils infested with P. cinnamomi or P. citricola, selections of WN may be useful as rootstocks for the walnut varieties ‘Hartley’, ‘Tulare’, and ‘Vina’.

Technical Abstract: Seedlings from seven open-pollinated selections of Chinese wingnut (Pterocarya stenoptera) (WN) representing collections of the USDA-ARS National Clonal Germplasm Repository at Davis CA and the University of California at Davis were evaluated as rootstocks for resistance to Phytophthora cinnamomi and P. citricola and graft compatibility with scions of five cultivars of Persian walnut (Juglans regia). Seedlings of Northern California black walnut (NCB) (J. hindsii) and Paradox hybrid (PH) (typically J. hindsii × J. regia) were used as standards. In greenhouse experiments potted plants of the rootstocks were subjected to intermittent flooding in soil artificially infested with the pathogens. All WN seedlings were relatively resistant to the pathogens (means of 0 to 36% of root and crown length rotted), compared to NCB (44 to 100%) and PH seedlings (11 to 100%). Negligible disease occurred in flooded control soil without the pathogens. In 9-year graft compatibility trials in an orchard, NCB and PH rootstocks supported relatively good survival and growth of all tested scion cultivars (‘Chandler’, ‘Hartley’, ‘Serr’, ‘Tulare’, and ‘Vina’; mean scion survival 80 to 100%, mean scion circumference increase 442 to 630 mm), whereas results with WN were mixed. Wingnut rootstocks from all sources were incompatible with ‘Chandler’ (scion survival 20 to 60%, scion circumference increase 7 to 161 mm). Conversely, all WN rootstocks from all sources were compatible with ‘Tulare’ and ‘Vina’ (scion survival 80 to 100%, scion circumference increase 380 to 620 mm). Use of the WN rootstocks produced variable results in ‘Hartley’ and ‘Serr’ (mean scion survival 10 to 100%, mean scion circumference increase 0 to 554 mm). Among trees with surviving scions, rootstock sprouts were more prevalent on WN than on NCB or PH rootstocks. In a commercial walnut orchard infested with P. cinnamomi, ‘Hartley’ survived and grew markedly better on WN selections than on PH. Resistance to P. cinnamomi and P. citricola was highly conserved among WN selections, which may be useful in walnut rootstock breeding efforts. Also, in soils infested with these pathogens, selections of WN may be useful as rootstocks for ‘Hartley’, ‘Tulare’, and ‘Vina’.