Studies On Posthavest Pathological Physiology Of Kuerle Fragrant Pear And Yali Pear

The physiological and pathological changes of Kuerle Fragrant pear(Pyrus bretchneideri Rehd.) had been studied,when it was artificially inoculated Penicillium expansum(Link) Thorn and Alternaria alternata (Fr.) keissl. Meantime, the anti- disease principle of Kuerle Fragrant pear was discussed in this paper in order to provide the theoretical fundementals for controlling pear post- harvest decay and elongating the post-harvest storage time.Frangrant pear has more anti-disease than Yali pear at 20 0C or so ; Penicillium expansum may result in more rapid speed of decay than Alternaria alternata when Fragrant pear and Yali pear are infected two pathogens.After Kuerle Fragrant pear was infected two pathogens , its respiratory metabolism and ethylene synthesis showed obvious changes. The respiratory rate and ethylene synthesis increased maximal value after the pear inoculated twenty four hours.The amount of respiratory rate and ethylene synthesis after infected P. expansum was far higher than that which infected A.alternata . In vitro it was proofed that P.expansum抯 body may produce ethylene. The maximal respiratory rate of Yali pear had been showed after two pathogens were inoculated 48 hours, and this was not beneficial to Yali?anti-disease.while Kuerle Fragrant pear was inoculated P.expansum and A.altemata, Kuerle Fragrant pear began to produce highly active enzymes of phenylpropaniodpathaways and chitinase. these phenomena comfirmed that these enzymes can harmonize each other and have equally important status in distribution of resisting disease . The amount of chlorogenic acid had changed over the same trendence as the activities of PAL and POD. The activities of chitinase also increased and showed systematization of induction, and two pathogens showed equal ability of induction . On the contrary, when Kuerle Fragrant pear and Yali pear were induced activities of PAL,POD and PPO two pathogens did not show equal ability of induction . The inducible ability of P.expansum was lower then that of A.alternata . PALand POD in Fragrant pear have more activity than that in Yali pear. On the contrary ,PPO in Yali pear has more activity than that in Fragrant pear.The hyphae of P.expansum could secrete higher activity of polygalacturonase and cellulase , but hardly secreted pectin and pectic acid lyse . P. expansum could rapidly macerate tissue and lead to a soft rot.When A.altemata infected Kuerle Fragrant and Yali pear, the activities of polygalacturonase and cellulase which hyphae secreted was lower than that of P. expansum抯 hyphae secreted. A. alternata could also secrete a little activities of pectin and pectic acid lyse , but speed of maceration was obviously lower than that of P. expansum , and showed wet rot.