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柑桔黄龙病在我国北部产区及南部高山发生得很轻微或完全不发生。在南部的重病区中,由于地势、防风林、间作果树等所造成的遮蔭条件也不利于病害的发生。大气候和小气候与黄龙病的相关有多种可能的原因。但首先应当研究它们对病毒传播媒介和侵染后发病的影响。用病芽作为接穗所长出的新梢在相当长时间内没有病状。最容易发病的是着果很多的幼树。初期发病的柑桔树通过重修剪和靠接辅助砧木的方法治疗有成功的实例。这些现象都可以从树冠树根比例与发病的关系来解释。柑桔类的种和品种间显然存在着耐病力的差异。这种差异也可能存在于同一品种的不同株系和个体间,因为用病区老树的接穗比幼树的接穗育成的苗木发病率较低。在黄龙病传播和流行上的许多不一致的现象还可能决定于病毒浓度和株系间毒力的差异及其相互关系。上述问题的研究可能导致栽培免疫、品种免疫和人工接种免疫方法的应用。
Citrus Huanglongbing occurs very little or not at all in the northern part of China and in the southern part of the country. In the southern heavily ward area, shade conditions caused by topography, windbreaks and intercropping fruit trees are not conducive to the occurrence of diseases. There are many possible causes for the relationship between the climate and microclimate and the yellow dragon’s disease. But first, their impact on the virus transmission vector and post-infection morbidity should be studied. Shoot buds as scions grow out of new shoots for a long time no symptoms. The most vulnerable is the fruit of many saplings. Early onset citrus trees have been successfully treated by re-pruning and by adjunctive rootstocks. These phenomena can be explained by the relationship between the proportion of crown root and incidence. Citrus species and varieties clearly exist between the differences in disease resistance. This difference may also exist in different strains and individuals of the same breed, because the incidence of seedlings of scion of old trees in the ward is lower than that of young trees. Many inconsistencies in the spread and spread of the yellow dragon’s disease may also depend on the differences in virus concentration and the virulence of the strains and their interrelationships. The above problems may lead to the application of cultivation immunization, variety immunization and artificial immunization methods.