枸杞鲜果霉变菌种分离鉴定及其生物学特性

为确定引起枸杞霉变的菌种类型,该文以采后鲜枸杞果实为材料,分离导致其霉变的菌种,经形态学特征及分子生物学特征鉴定确定类型,并对与其霉变速率相关的部分生物学特性进行研究。结果表明:从霉变的鲜枸杞中共分离出6株致霉菌,分别鉴定为:菌种1为镰刀菌、菌种2为交链孢霉、菌种6为尖孢镰刀菌、菌种7为青霉菌、菌种11为串珠状赤霉菌及菌种21为草酸青霉。经过回接试验发现6种霉菌均能使健康枸杞鲜果霉变,从这些病斑中再次分离得到相同霉菌。6种菌的致死温度不同,最高致死温度为54℃。菌种1的最适生长温度为40℃,菌种6的最适生长温度为35℃,其余4株菌的最适生长温度均为25℃。6种菌在相对湿度为30%~90%范围内均能生长,最适生长相对湿度为75%~85%。最适p H值范围为4~8,p H值为6时霉菌孢子萌发率最高。通过对6种霉菌与温度、相对湿度、p H值3个与干燥参数相关的生物学特性研究,为今后鲜枸杞干燥过程条件的控制提供理论依据。

Isolation, identification and biological characteristics of pathogenic fungus from Chinese wolfberry fruit

Chinese wolfberry fruit is the mature fruit of Ningxiawolfberry. It contains rich bioactive substances and nutrients, such as wolfberry polysaccharide, total sugar, amino acids, betaine, carotene, niacin and trace elements etc. It has the function of immune regulation, anti-tumor, antioxidant, anti-fatigue, lowering blood lipid and blood sugar, etc. The mature period of wolfberry fruit is from June to September, and flowering, fruitage and maturation at the same time. The fresh Chinese wolfberry fruit is easy to get mildew due to its thin peel, high moisture and sugar content. Under normal environment and without any treatment, mildew will occur within 1 day after wolfberry fruit being picked. The mildew rate will reach 30%-40% 2 days later, and as high as 50%-80% after 3 days. Commodity value of the mildewed wolfberry is seriously lost. The reproduction of microorganisms is the cause of mildew. Drying process is commonly used to prolong its shelf life. At present, the drying methods mainly include natural drying and hot air drying. However, mildew is still serious during the early stage of drying process due to the varieties of pathogenetic mould. In order to study the mildew problem of Chinese wolfberry, the pathogenetic mould were isolated from the fresh Chinese wolfberry fruit and identified by morphological characters and identification. The biological characteristics related to mold rate were determined. Six strains were isolated from the moldy Chinese wolfberry fruit, which are 1Fusarium species, 2Alternariasp., 6Fusarium oxysporum, 7Penicilliumsp., 11 Gibberella fujikuroiand 21Penicillium oxalicum. When the mould was separated, the single colony on the culture medium was counted. The strains were identified by optical microscopy. Fungal separation test isolated 58 fungal single colonies. The detection rate ofFusarium and green fungus was the highest. Artificial infection test showed that all of these six molds were able to cause health Chinese wolfberry fruit mildew, and the same moulds were isolated again from the mould spots. The lethal temperatures on these six strains were difference. The highest was 54℃. Six strains stopped growing at this temperature. The optimal growth pH value of six strains ranged from 4 to 8, with the highest mould spore germination rate at pH value 6. Six strains could grow when the optimal growth relative humidity was from 30% to 90% with the most optimal range between 75% and 85%. The pathogenic fungus which caused the rot of fresh wolfberry were isolated and identified, the effects of temperature, humidity and pH value on the growth of mold were studied. Together, these results provide the theoretical basis for the control of microorganisms growth, and also provide technical support for Chinese wolfberry storage and drying process in the future.