| The Picea plant is the main forest-building species in the high mountains of southwest and northwest China.There are about 35 species of spruce plants in the world,including 16 species and 9 varieties in China,and 11 species and 2 varieties in Sichuan.Spruce,as one of the most important tree species for forest management in Sichuan,has important value in economy,ecology and society.However,in recent years,the needle cast disease of spruce plantation forests has become more and more serious,and its occurrence scope has expanded to the entire spruce distribution area in Sichuan.Therefore,in this study,six spruce tree species distributed in erlang mountain forest farm in luding county,shenmulei in baoxing county,were used as research tree species.To explore the difference of resistance of different tree species to spruce needle cast disease and to screen the morphological indicators of resistance to needle cast disease,the relationship between the stomatal phenotype and microstructure of 1 and 2 year old needles of different tree species and needle cast disease was analyzed.In addition,the correlation between the stomatal phenotype and microstructure of 1 and 2 year old needles of three tree species and needle cast disease within one year was studyed.These results will provide scientific and theoretical basis for breeding excellent disease-resistant tree species.The research results are as follows:1.There were significant differences in the disease resistance of eight spruce species,and they were divided into the following categories by calculating the disease index under natural conditions(the numbers in parentheses are the susceptibility index): medium resistant tree specie,Picea likiangensis(35.21);low susceptible tree species,Picea likiangensis var.balfouriana(52.33);medium susceptible tree species,Picea retroflexa(72.91)and Picea asperata(74.59);highly susceptible tree species,Picea Brachytyla(84.66)and Picea complanata(86.25).2.There were significant differences in the stomata phenotypes between 1 and 2 year old needles of different spruce trees.Especially,the stomatal line density,stomatal area density,stomatal line number and stomatal length at different leaf ages were significantly or very significantly positively correlated with the disease index.However,the stomatal lateral spacing and stomatal depth had a significant negative correlation with the disease index.In addition,the longitudinal spacing of the stomata and the area of the stomata had no significant correlation with spruce needle cast disease.Therefore,stomatal line density,stomatal area density,stomatal line number,horizontal stomatal spacing,stomatal length,and stomatal depth in needle can all be used as morphological identification indexes of spruce resistance to needle cast disease.3.The thickness of the cuticle on the surface of spruce needles is a structural barrier to resist and delay the invasion of pathogens.The greater the thickness of the cuticle,the stronger the resistance of spruce to needle cast disease.In this study,it was found that the cuticle thickness of 1 and 2 year old needles was significantly negatively correlated with the index of needle cast disease,and the correlation coefficients were-0.86 and-0.87,respectively.Therefore,the cuticle thickness can be used as a quick method to identify the resistance of spruce.In addition,the thickness of the epidermis and the thickness of the hypodermis in the 1 and 2year old needles were no significant correlation withe the resistance of spruce.4.The stomatal phenotype and microstructure of 1 year old needles had the greatest changes from August to September.In August,needles had the largest stomatal line density,stomatal area density,and stomatal line number,and the lowest stomatal spacing,stomatal depth,and cuticle thickness.However,there was little change in these characteristics between September and December.In addition,the stomata phenotype and microstructure of 2 year old needles showed little change at all periods.In general,spruce with deeper coniferous stomata depth,fewer stomata numbers,less dense arrangement and thicker cuticle layer are more resistant to spruce needle cast disease.In the subsequent process of plantation,we can choose the corresponding Spruce for afforestation. |
