译 名：
ON THE RESISTANCE OF APPLE TREES TO THE INVASION BY VALSA MALI MIYABE ET YAMADA:OBSERVATIONS ON THE RELATIONSHIP BETWEEN WOUND HEALING CAPACITY OF APPLE BARK AND THE LEVEL OF RESISTANCE
作 者：
Chen Ce Liu Fuchang Xing Zufang Zham Xuewei Shi Xiuqin Guo Jingei (Institute of Pomology,Chinese Academy of Agricultural Sciences)
Chen Yenhsi (Department of Plant Protection,Beijing University of Agriculture)
摘 要：
In View of the nature of latent infection by the causal fungus,Valsa mali Miyabe et Yamada,the writers emphasized investigation on the mechanism of resistance of apple tissue against latent invasion.Ⅰ.Apple twig sections were adjusted to different levels of moisture content,wounded by scorchingthe bark,and then placed under controlled conditions at different temperatures.Microscopic examinationof bark tissues surrounding the Wounds showed that no lignification and periderm formation occuredin twigs with moisture content of 83% relative turgidity at 12℃.In the range from 16 to 24℃,lignifi-cation and periderm formation accelerated with the increase of temperature.It was observed that thewound healing process proceeded well in the twigs with moisture contents above the level of 80% relativeturgidity,and the healing activity declined quickly with the decrease of bark moisture.Three groups oftwig sections,adjusted to different levels of moisture content,were inoculated with equal quantities ofmycelial mass and the rates of canker growth were measured.The measurements showed that the advan-cing rate of invading hyphae varied inversely with moisture contents of twig bark,indicating that twigswith stronger healing capacity were more resistant to fnngal invasion.2.In field,canker development and wound healing rate varied significantly with seasons.The max-imum incidence of Valsa canker occured in early winter and spring,i.e.the dormant period ofapple trees,when the healing activity was weak.In May and June,the disease potential declined,andthe lesions ceased to develop,when vigorous growth of apple trees resumed and the healing process wasaccelerated.In August and Semptember,a number of new lesions appeared,nevertheless the woundhealing process was still in vigorous condition,The development of the new lesions was almost restrictedto the dead wrinkled(rhytidomous)tissues.consequently,most of the cankers produced in summer andearly autumn were superficial.Some of the cankers might develop more deeply into the inner barkbut only to a limited extent.During early winter period,the buphae in the superficial canker-tissues sank into the inner bark through the periderms beneath,leading to necrosis of the healthy backtissues and serious damage in dormant season.3.Measurements of the light fruiting and the beavy fruitinrg trees or brahches revealed a highermoisture content,a more active wound healing activity,and a less canker growth in the fomer teethan in the latter,These facts suggested the close relationship between the nutrient level,water phys-iology,wound healing capacity,and the level of resistance to fungal invasion.
