Abstract

In order to clarify the responses of different chestnut cultivars to Cp-toxin stress, the effect of Cp-toxin from Cryphonectria parasitica (Murr.) Barr on Castanea mollissima Blume, especially on its cell structure, was examined. Chestnut shoots of both resistant (Beiyu No. 2) and susceptible (Hongguang) cultivars were treated with Cp-toxin for 24, 36, 48 and 72 h, respectively, and then electrolyte leakage (EL) and malondialdehyde (MDA) contents were measured in the leaf tissues. Also, ultrastructural changes of organelles were observed under transmission electron microscope. The results show that the EL and the MDA content increased notably when leaves were treated with Cp-toxin for 72 h, and the content of MDA and EL was 4.36 and 2.19 times that of the control samples, respectively. The damages on membrane systems of the cells were lighter and they occurred later than expected in the resistant cultivar than in the susceptible cultivar. At the treatment time of 72 h, Cp-toxin caused marked damage effects on membrane systems of chloroplasts and mitochondria. Finally, after 72 h treatment with Cp-toxin, the membrane systems were damaged, after which EL and the MDA contents increased and were significantly higher than those of the control (P＜0.01), while the plasma membrane and cell wall broke into pieces. The change of cell ultrastructure in different cultivars of chestnut in response to inoculation with C. parasitica that positively correlated with the resistance to the chestnut blight can be used as a criterion to evaluate disease resistance.

Key words: Castanea mollissima, Cryphonectria parasitica, Cp-toxin, cultivars, ultrastructure.