ISHS Acta Horticulturae 705: V International Walnut Symposium
INTERACTION OF JUGLANS SPECIES WITH PRATYLENCHUS VULNUS AND MELOIDOGYNE INCOGNITA |
| Authors: | T. Buzo, M. McKenry, J. Hasey |
| Keywords: | J. hindsii, J. regia, J. hindsii × J. regia, own-rooted, micropropagated, primary roots, secondary roots, fleshy roots, nematodes/gram root, susceptible |
| Abstract:
Nematode-free micropropagated own-rooted English cultivars ‘Vina’ and ‘Chandler’ and seedling rootstocks Northern California black (NCB) and Paradox hybrid were planted into a 0.5 m3 hole of sandy loam soil containing 100 Pratylenchus vulnus and two Meloidogyne incognita per 250 cm3 of soil volume. Trees were farmed using micro-sprinkler irrigation with a 3 m by 4 m plant spacing. Trees were removed from the field site after 7 months and all new root growth partitioned into three size groupings including fleshy root tips, secondary roots (<7 mm diameter), and primary roots (>7 mm diameter). These two nematodes preferred the fleshy root tips supporting 172, 293, 369 and 882/gram of root on NCB, Paradox, ‘Vina’, and ‘Chandler’, respectively. Secondary roots supported 22, 117, 204 and 239/gram of root on NCB, Paradox, ‘Vina’, and ‘Chandler’, respectively. Few nematodes were present in primary roots although these roots were produced in the presence of inoculum. All Juglans spp. tested were susceptible or highly susceptible to P. vulnus. NCB was a poor host and non-galled by M. incognita, Paradox was intermediate, and the two J. regia cultivars proved susceptible. When present, the root knot galls were normal-sized and occurred across the root system, but never on the fleshy root tips. Paradox and J. regia cultivars occasionally developed 3 to 5 cm diameter galls on their secondary roots. Planting into high populations of these nematodes can greatly restrict early root exploration by Juglans spp. Total tree biomass at termination of the experiment ranged from 3.9 kg/tree for the more vigorous Paradox to 2.3 kg/tree for own-rooted ‘Vina’. This difference was significant at P ≤ 0.05 with other growth differences being intermediate and non-significant. | |
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