Preliminary Studies Of Biological Characteristics Of Pitaya Neoscytalidium Dimidiatum And Prevention And Control Of Indoor

In recent years many pitayas were planted together. Once the diseases were found,it will be spread very rapidly,and hard to control. According to the investigation of Huizhou city in Guangdong province,we found that the pitayas were damaged by several pathogens. It cause a serious damage on the dragon fruit industry development. In this research,we had already isolated and purified twelve fungus from the pitaya stems which had disease symptoms.Base on Koch’s law, we tested the pathogenicity of these twelve fungus. The results show that two of them have high pathogenicity. We identified that these two isolated were Neoscytalidium dimidiatum, which can caused pitaya stem and fruit canker. Once the stem or furit infected with this pathogen, in the beginning,the color of the spots wers pale green. In the later infection period, gray erumpent spots were on the surface of the infection area. Eventually the stem or fruit tissues were die with canker.The results was as follows:(1)The hypha of Neoscytalidium dimidiatum on the PDA medium was colorless in the early stage, after 3 days later they turn to taupe. Neoscytalidium dimidiatum have three kind of spores:arthrospre, chlamydospore and conidia. The most fitness pH value is 4-6, the growth rate will down regulated significantly beyond this pH value.The Light intensity and light application time were not limit factors during its growth.(2)We analysis the inhibitory of 20 fungicides. Among that six fungicides had good effective on this disease, even in the low concentration. These fungicides can be considered as effective fungicides to used in the field.In the same time,we also do some research on the biological control. The results show that the 3 strains which were isolated from banana roots and soil can inhibit the hypha of Neoscytalidium dimidiatum.(3)To investigated the resistance of different pitaya cultivars,we infected with Neoscytalidium dimidiatum on eight cultivars healthy stems. Then we found that "Yellow pitaya" was resisitance cultivars of Neoscytalidium dimidiatum. The best solution to control pitaya canker was use agricultural control and chemical control together, eliminate the pathogen, and selected resistance cultivars. Aim to selected a effective fungicide to control this disease.(4)As we all know,fungus from different areas have different pathogenicity. Then we isolate the canker pathogens from Guangzhou,Huizhou,Hainan and Guangxi.and then test their pathogenicity,we found that pathogen from Hannan province has the highest pathogenicity, pathogen from Guangzhou show the lowest pathogenicity.(5) In the other side, we also do some research on the pitaya fruit postharvest. Postharvest diseases cause lots of losses to harvested pitaya fruits during storage and transportation. In order to study the effects fo 4 different preservative agent on postharvest quality of pitaya fruits infected of Neoscytalidium dimidiatum. Compared the respiratory intensity, fruit weight and relative permeability value,the results suggested that the preservative agent used in citrus is a good preservative agent used on pitaya fruit.