Distribution Characteristics Of Juglans Regia Diseases In Wild Walnut Natural Conservation Area In Xinjiang,China

The species Juglans regia,which belongs to the genus Juglans in the family Juglandaceae.J.regia,endangered species,is a valuable relic and of the tertiary temperate broad-leaved forest.In Asia,a large area of J.regia,is only distributed in Wild Walnut Natural Reserve,Gongliu County,Yili Prefecture,Xinjiang,China.Serious walnut disease leads to a reduction in the fruit bearing rate of walnut trees,the tree vigor is weakened,the life span is shortened,and even the plant is dead.The transect method was used to investigate the diseases of J.regia in four slope aspects of Wild Walnut Nature Reserve in Xinjiang.Statistical analysis of the distribution characteristics of four J.regia diseases and their different disease grades in different slope aspects,different age classes,different height classes,and different crown width classes,quantitative distribution characteristics of four diseases and their different disease grades in J.regia components（diameter at breast height,tree height,crown width）and the correlation between disease types and disease grades with various components of J.regia and slope aspects.The purpose is to provide basic data on disease types and disease grade distribution of J.regia,and provide scientific reference for the protection of J.regia and the management of protected areas.The main findings are as follows:1)The main disease of J.regia in the reserve is walnut brown spot disease（the proportion of diseased plants is 95.8%）,walnut deadwood disease（90.5%）,walnut black spot disease（74.4%）and walnut rot disease（7.7%）.The proportion of diseased plants of the four diseases decreased with the increase of disease grades（grades 1 to 4）.2)In the four slope aspects,the proportion of walnut brown spot disease is 20.4%to 28.1%,walnut deadwood disease is 18.7%to 26.8%,walnut black spot disease is 14.2%to 24.6%,with the highest proportion of diseased plants on the shady slope.The proportion of diseased plants with grades 1 to 4 of walnut brown spot disease,walnut deadwood disease,and walnut black spot disease in J.regia from four slope aspects varies greatly.The total of grade 3 and 4 walnut deadwood disease,walnut black spot disease and walnut brown spot disease were 14.9%～21.4%,23.2%～36.6%,15.4%～25.8%.3)The proportion of diseased plants of walnut brown spot disease,walnut deadwood disease and walnut black spot disease is the largest in the middle age trees（69.5%、66.2%、53.5%）and the smallest in the young trees（3.6%、2.6%、3.0%）.No diseased seedlings were found.Walnut rot disease only occurred in old trees.The proportion of diseased plants of the four diseases of J.regia at different age classes varies greatly from grade 1 to 4.4)J.regia is susceptible to walnut brown spot disease（61.3%）,walnut deadwood disease（59.4%）,and walnut black spot disease（47.9%）at height class H₄ to H₅（6.0 to 12.0 m）,and is relatively susceptible to walnut rot disease（3.5%）at height class H₆（12.0 to 15.0 m）.The proportion of diseased plants of the four diseases of J.regia at different height classes varies greatly from grade 1 to 4.5)J.regia is susceptible to walnut brown spot disease（71.0%）,walnut deadwood disease（67.1%）,and walnut black spot disease（56.9%）at the 3rd to 4th crown width classes,and is relatively susceptible to walnut rot disease（1.8%）at the 6th crown width class.The proportion of diseased plants of the four diseases of J.regia at different crown width classes varies greatly from grade 1 to 4.6)J.regia with walnut brown spot disease has a relatively uniform size of DBH,tree height,and crown width at the same disease grade,indicating that when the sizes of DBH,tree height,and crown width are similar,the pathogen infection intensity and infectivity of the four diseases are the same.7)There was significant positive correlation of DBH,tree height and crown width of J.regia with walnut brown spot disease,walnut deadwood disease,walnut black spot disease,and walnut rot disease（P<0.05）.Walnut black spot disease had significant negative correlation with slope aspect（P<0.05）.Different disease grades of the same disease are significantly correlated with the DBH,tree height,crown width,and slope direction of J.regia（P<0.05）.