Enhanced Hatching of Globodera tabacum solanacearum Juveniles by Root Exudates of Flue-cured Tobacco.

Stimulation of hatching of a tobacco cyst nematode (Globodera tabacum solanacearum) by root exudates from resistant NC 567 and susceptible K 326 cultivars of flue-cured tobacco, Nicotiana tabacum, was investigated. Root exudates were collected by soaking seedlings in deionized water for 2 hours at 22 degrees C in the dark. Fifteen mature and uniformly sized cysts were exposed at 15, 20, or 25 degrees C to undiluted root exudate, root exudate diluted 1:1 or 1:3 with deionized water, or deionized water alone. Hatched juveniles were counted and removed at weekly intervals during 42 and 53 days of exposure in experiments conducted in 1994 and 1995, respectively. Root exudates from both susceptible cultivar K 326 and resistant cultivar NC 567 stimulated more hatching than deionized water at 25 degrees C in 1994, and at all three tested temperatures in 1995. In 1994, dilution of root exudates 1:3 reduced stimulation of hatching at 25 degrees C compared to undiluted exudate. Hatching at 25 degrees C was similarly stimulated by exposure to undiluted root exudate and exudate diluted 1:1. In 1995, both dilutions reduced stimulation of hatching by root exudates at all the temperatures.