Observations on the host-parasite relationship of Pratylenchus vulnus on grapevine, Vitis vinifera.

Studies on the host-parasite relat ionship of Pratylenchus vulnus Allen and Jensen to roots of several major crops have shown that this nematode feeds on cortical cells, an activity which causes extensive damage (2, 3). Similar informat ion is not available for grape, al though the association of P. vulnus with root injury on grape has been repor ted (1, 7). T h e purpose of the present study was to investigate the host-parasite relat ionship of P. vulnus on grape vat. ' T h o m p s o n Seedless' and the nematode 's effect upon root tissues. Two-bud grapevine cuttings were obtained in November 1973 and placed in cold storage, Eighteen of the cuttings were transplanted, in mid-February 1974, singly into 20-cm clay pots containing autoclaved sandy loam soil. Pratylenchus vulnus was cultured monoxenical ly on carrot slices (4). T e n days after being transplanted, one-half of the plants were inoculated with an aqueous suspension of 1,000 nematodes /po t . Inocu lum was poured into 10 holes in the soil of each pot at 5 to 7.5 cm from the grape stem. Pots were placed in sawdust beds in a greenhouse and irr igated at 1to 3-day intervals with distilled water as needed. Half-strength Hoagland ' s nut r ient solution was provided weekly. Soil temperature was main ta ined at 20-30 C, except for a 5-week dormancy period dur ing the winter when greenhouse heaters were turned off and soil t empera ture dropped to 5-16 C. Dur ing this dormancy period, tops of plants were pruned. After 362 days, r andom root sections from inoculated and noninoculated plants were selected for examinat ion. Roots were cut into pieces 10 cm or less in length and stained in a solution of lactophenol with 0.05% acid [uschin. Freehand transverse and longitudinal sections were cut from necrotic and healthy-looking roots of bo th inoculated and noninoculated material. Sections were moun ted on slides and examined microscopically.