Research On Poplar Leaf Veins Spot Pathogen And Occurrence Regularity

Yang Ye grain spot, also called Yang Ye blight disease, is a generally occurred disease in northeast, northwest, north China and other re gions in recent years. Zhenyu Zhao firstly reported Xinxiang poplar leaf veins spot dise ase in 1979. The disease m ainly happens on the poplar leaves, severely even can lead to plant leaf all die or early fall of f; promotes the process of poplar decline sharpl y. Therefore, we collected typical disease sam pies from Urumqi, Shihezi, Alear City, Manas County, Xayar County for tissue culture and purification and determination of pathogenic and pathoge nic bacteria. This study observed annual accumulation and disappearance dynamic of di sease happening and their relationship with meteorological factors; researched the p athogen wintering site and in fect ways of this pathogen; surveyed the resistance of pathogenic bacteria of different poplar varieties. T he main results were as follows:(1) Different types of disease leaves collected from different areas were cultured and purified. The results sh owed that the 268 pieces of ti ssue are separated and obtained 237 pieces of fungi. Accord ing to characteristics of the colony and their conidium under the microscope, morphology of strains separated from different types of disease samples from different places had a rem arkable difference. Roughly, they can be divided into Alternaria, Fusarium, Trichoderma, Verticillium. We determined the pathogeni city of these strains by using the morphology and m olecular biology, and Alternaria alternate had the strongest pathogenicity.(2) In 2014 and 2015, annual a ccumulation and disappearance dynamic of poplar leaf veins spot were recorded. Date analysis results showed that diseases begin to show symptoms from the beginning of May, at the end of July by the middle of August is full incidence period, September early illness gradually alleviate, then end in October. We systematically analyzed the impact of meteorological factors on the occurrence of Poplar leaf veins spot. The study showed that the highest tem perature, air relative humidity, sunshine duration, average vapor pressure, average wind velocity direct ef feet to disease occurrence decreased successively Disease severity had a very significantly nega tive correlation with sunshine duration and sunshine duration, had a significant positive correlation with air relativ e humidity, sunshine duration, and the highest temperature.(3) In December 2015 and March 2016, we co llected defoliation, twigs, bark, and overwintering bud organization, then isolated and cultured their pathogen, in addition, had a microscopic examination on overwintering bud or ganization. The results show that the pathogen separation rate from defoliation collected in December 2015 is as high as 55.56%, the pathogen separation rates from bark and overwintering bud or ganization are 2.68%, no bacteria colonies on twigs; th e pathogen separation rate from defoliation collected in March 2016 is 36.7%, the pathogen separation rate from overwintering bud or ganization is 3.3%, there is no bacteria colonies on twigs and ba rk. Microscopy found pathogens did winter over in the form of mycelium and conidium mainly on the leaves. Thereby, we could deduce that the next year disease occurs early infected by conidium on defoliation. The study of Pathogen infection way showed that pathogenic bacteria mainly infect tender leaf and leaves around them through natural openings and wound.(4) According to the survey of 6 poplar varieties infected leaf veins sp ot disease in the field, we known that the incidence of populus al ba and small little is above 35%, both the m belonged to susceptible variety; Lombardy poplar and mass Yang had less than 1% incidence, belonged to high varieties. Dif ferent poplar varieties were inoc ulated with agar disk, spore suspension, crude toxin of strong pathogenic bacteria, and the results showed that the resistance of dif ferent poplar varieties is di fferent significantly because of inoculum and inoculation methods. There are certain lim itations on the disease resistance for indoor varieties; they couldn't fully reflect the resistance of varieties in the field.