核桃叶斑病病菌菌丝体及孢子越冬存活研究

Study on Overwintering Survival of Mycelia and Conidia of Walnut Leaf Spot Pathogens

【目的】研究核桃叶斑病病原菌Alternaria alternata的越冬方式及场所,为该病害的防控提供理论依据。【方法】2016、2017年连续两年11月～翌年3月在洛浦县五个乡镇的观测园内,采用常规组织分离法、固体平板稀释涂布培养计数法,对病原菌菌丝体在不同器官组织、分生孢子在不同生境以及病原菌在土壤不同深度的存活情况进行调查。【结果】核桃叶斑病病原菌主要以菌丝体在病落叶及树上病叶上越冬,分离率高达90%,其次是芽和主干树皮,分离率为87.67%、79.58%,而一年生侧枝及果实的病菌分离率较低;该病菌也可以分生孢子在树上、地表、土层5、10、15、20、30 cm病残体上越冬,其中10～15 cm土层病菌孢子的存活率最高,而30 cm处病菌孢子存活数量很少;并且发现该病原菌在0～20 cm的土壤中均能越冬,且土层越深病原菌存活数量越少,地表土的病菌数量与土壤中存在显著差异(P<0.05)。【结论】核桃叶斑病病原菌可以菌丝体及分生孢子在病植株上、土壤病残体上及土壤中越冬。

【Objective】To clarify the overwintering mode and site of the pathogen of walnut leaf spot disease caused by Alternaria alternata in the hope of providing a theoretical basis for the prevention and control of the disease.【Method】In 2016 and 2017,for two consecutive years from November to March in the observation gardens of five townships in Luopu County,the survival of pathogenic mycelia in different overwintering sites,conidia in different habitats and pathogens at different depths of the soil were investigated by general tissue separation and culture counting method of solid plate dilution coating.【Result】The pathogen of walnut leaf spot disease overwintered mainly on the diseased leaves and trees,and the isolation rate was as high as 90,followed by bud and trunk bark,and the isolation rates were 87.67%and 79.58%,respectively.But the isolation rate of annual lateral branches and fruits was lower.The pathogen could also survive the winter on the tree,surface and soil layers of disabled bodies of 5,10,15,20 and 30 cm.,and the survival rate of the spores was the highest in the soil layer of 10-15 cm.However,the number of spores in 30 cm was very few,and it was found that the pathogen could survive winter in 0-20 cm soil,and the deeper the soil layer was,the less the number of pathogen was,and there was significant difference between the number of pathogen in topsoil and that in soil(P<0.05).【Conclusion】The pathogen of walnut leaf spot can survive winter in the form of mycelia and conidia on the diseased plants and plant residues in different habitats and soil.