Published online by Cambridge University Press: 16 January 2013
Introduction. Bacterial canker, caused by Pseudomonassyringae pv. syringae, is a damaging disease of stone fruitworldwide. The effects of rootstock, temperature and incubation duration on bacterialcanker in peach were assessed using both field and laboratory inoculation assays.Materials and methods. Both field and laboratory experiments were conductedto study the effects of rootstock, temperature and incubation duration on disease severityin peach. All inoculations were achieved with P. syringae pv.syringae strain B3A. Bacterial inoculations were applied to 1-year-oldshoots of peach trees [Prunus persica (L.) Batsch]. After inoculation,the inoculated shoots were allowed to incubate either under field conditions or in a coldroom at different temperatures [constantly at 0 °C, constantly at 14.4 °C, and in afluctuating temperature regime of 12 h at 0 °C (night) and 12 h at 14.4 °C (day)] forexcised shoots. The lesions were determined 1 to 6 weeks after inoculation to determinethe effect of incubation duration. Results and discussion. The fieldexperiment using peach grafted on three rootstocks (Nemaguard, K119-50 and P30-135) showedthat shoots on Nemaguard developed the longest lesions and shoots on K119-50 the shortestamong all three rootstocks. Shoots on Nemaguard had significantly lower bark calcium andhigher nitrogen concentrations than those on K119-50 and P30-135. A negative correlationwas found between lesion length and bark calcium concentration and the [calcium/ nitrogen] ratio. Laboratory experiments with excised shoots on Nemaguard, K119-50,P30-135, Lovell and Guardian rootstocks growing in a second orchard showed inconsistentresults. Shoots from Nemaguard developed significantly smaller lesions than those onK119-50 and P30-135. Shoots on Guardian and Lovell also developed significantly smallerlesions than those of shoots on K119-50 and P30-135. Temperature fluctuation duringincubation (0 °C to 14.4 °C) had no effect on shoot lesion length compared with thoseincubated constantly at 14.4 °C, but produced significantly longer lesions than shootsincubated constantly at 0 °C. These inconsistent results suggest that, in the absence ofmajor predisposing factors (i.e., ring nematodes or low soil pH),rootstocks may play a minor role in peach susceptibility to bacterial canker even underfavorable disease development conditions.