| Casuaina spp. ohnson is a very important shelterbelt specie for Southern China littora.The shelterbelts,built in1950s,old and insect damaged,need to be reforested in a near future. Some studies about Anoplophora chinensis (Forster) resistance selections among the48Casuaina strains and its resistance mechanism were performed for the purpose of providing Anoplophora chinensis resistance selections.The main results are as follows:1. The resistance Casuaina strains selectionThe growth characteristic and the stress tolerance in the48Casuaina strains are different. The result of July,2011experiment shows that the average diameter at breast height(DBH) differs from4.00to8.00cm,and the survival rate differs from30.0%to100.0%.The results of the2010to2012survey research show that the injury severity rate differ from one Casuaina strain to anther,but share the very similar regularity.The life cycle lasts about1year,from June to next June.The infested trees ratio and larval population density reach the maximum in Aug., for incubation boom.Then they decrease and stabilize in Oct.,as most of young larvae die.Such status last until the larve pupate the next Apr..The cluster analysis result shows the48Casuaina strains can be divided into3groups,which is upon the average DBH,the survival rate,the infested trees ratio and larval population density.The first group contains17strains.They are Dongshan2,Hui28,Kangfeng,Zhanjaing2,Hui37,Kang8,Guangdong601,Guangdong A14, Nanshan7,Long7-18,Nanshan8,Guangdong A1-3,Hui19,Hui95,Hui13,Hui76and Hui83.The second group also contains17strains,Guangdong503,Pingtan2,Zhanjiang1,Zhanjiang,Guangdong701-2,Hui2,Hui86,Guangdong701-3,Hui1,Hui45,Hui77,Guangdong A8-2,Kang2,Kang3,Hui59,Kang1,Zhanjiang3.The third group contains14strains,Dongshan9201,Guangdong A13,Hui12,Hui18,Long4,Guangdong501,Guangdong A1,eutian20,Hui88,Guangdong Zajiao,Hui98,Hui78,Hui65,Hui58.The first group strains are alternative materials for shelterbelts reforestation,especially the high resistance capability ones,such as Hui83,Hui76and Hui13.While the48Casuaina strains are all good wind withstand materials,The selection shuold focus in Anoplophora chinensis resistance or Lymantria xylina Swinhoe resistance,as appropriate.As an example,Quanzhou district,suffering from Anoplophora chinensis,should choice Hui83,Hui76and Long7-18for example.And Regions like Putian City which once suffers for Lymantria xylina should choice Hui83,Hui76,Zhanjiang3and Guangdong A8-2et al.2. The life cycles of Anoplophora chinensis on different Casuaina strainsEach of Anoplophora chinensis’s stage has different sensibility to Casuaina defense behaviors.The feeding choice test shows that Anoplophora chinensis adult have a higher feeding frequency and a bigger feeding area on first group Casuaina sprays.For instance,the first group strains Hui76has a eeding frequency of0.056and a feeding area of3.24cm2, while the second group trains Guangdong A8-2has0.185and67.19cm2.The feeding choice of adult can affect the oviposition choice for its flight range is8to10m.The oviposition choice test shows that the oviposition rate goes with trunk exterior roughness,which can enhance tarsus grip of female adult and contribute the oviposition.The hatch test results that there is non-significant difference among the three groups of Casuaina even they differ in moisture contentThe young mortality test shows that the young mortality of Anoplophora chinensis is higher in the high resistance strains in Aug. to Oct..Take the high resistance strain Hui13and the low resistance one Hui58as an example.Hui13has a tree infested dropping rate of95.58%and a larval population dropping rate of97.35%,while Hui58has20.04%and23.92%instead.The eclosion test shows that the high resistance strains have the lower eclosion rate.All in all,the resistance is mainly working on adult’s feeding choice,the oviposition choice to trunk bark from,the young mortality and the eclosion.3. The difference of inclusions contains of Casuaina and it’s resistance mechanismAccording to the cluster analysis dendrogram,the Hui83,Hui76and Hui13are good contrasts to Putian20,Hui88and Hui58,for they are two extremes.The Guangdong A8-2,Hui1and Pingtan2are second group strains, which were large area cultivation.All these strains are chosen for resistance mechanism study.Trunk exterior roughness test shows the bark from variate from strain to strain.The gradation on the9strains which is based on lenticel density and leticel fissure depth.The Hui831st grade,Hui761st,Hui133th,Guangdong A8-23th,Hui12ed,Pingtan21st,Putian203th,Hui582ed,Hui883th.In general,the higher resistance strains have the rougher bark form and the higher oviposition rate. The experiment on health trees shows the higher resistance strains have the higher contains of total phenols,tannin and flavone and lower contains of protein,soluble sugar and polysaccharide in their phloem and xylem.The experiment of Anoplophora chinensis infestation stimulation shows the6kinds of inclusions contains change in both phloem and xylem,but not the same pattern.But all the strains share the very similar regularity in the same parts of the tree.First of all total phenols,tannin and flavone contains drop.Next soluble sugar contains rises.Then soluble sugar contains descends,with the rising of total phenols,flavone and polysaccharide contains.The experiment of the correlation between inclusions contains and young mortality of Anoplophora chinensis results that the mortality has a positive correlation with total phenols,tannin and flavone contains of xylem,and with total phenols,tannin and soluble sugar contains of phloem.The resistance grade has a higher correlation with protein,soluble sugar and polysaccharide contains than other3inclusions.For instance,the correlation of the tree infested dropping rate and the contains of total phenols,tannin,flavone,protein,soluble sugar and polysaccharide are67393,0.55128,0.47271,0.31318,0.25286,0.27846.The experiment of the correlation between inclusions contains and eclosion shows that the eclosion has a higher correlation with protein,soluble sugar and polysaccharide contains than other3inclusions.In conclusion,There is two aspects of resistance of Casuaina to Anoplophora chinensis,movphologic resistance and chemical resistance.The morphologic resistance contributes by smoothing the trunk bark,while chemical resistances increase the secondary inclusions and descend the nutrient inclusions,which causes the young mortality and malnutrition of Anoplophora chinensis. |
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