Selection Of Clones And Harvest Sprouts By Short Rotation Based On Quality Cellulose In Black Locust (Robinia Pseudoacacia L.)

Black locust?Robinia pseudoacacia L.?has the characteristics of rapid growth,strong sprouts,large biomass,strong drought and leanness endurance,and widely suitable area.Nowadays,black locust has been cultivated and managed as firewood forest species in many areas.With the crisis of the international fossil energy,the development and utilization of biomass energy attracted much attention.Black locust as a lignocellulosic feedstock tree has gradually entered people's vision,but there is a gap in the technology of selecting and breeding black locust with high cellulose content.This study focused on lignocellulose to research on selection of clones and harvest sprouts by short rotation in black locust.The black locust clones were collected from nine places of origin,and their variation of phenotypic and chemical character were analyzed to select quality black locust clones with high cellulose content.Microsatellite markers?SSR?were used to evaluate the genetic diversity of black locust populations and to construct the core collection.By investigating the growth of sprouts from black locust short rotation in western of Henan Province,the variations of total lignocellulose and lignocellulose content were discussed.Meanwhile,the method of steam explosion was used to explore the effective ways to increase yield of cellulose.A system based on high cellulose content of selected quality black locust clones,harvested sprouts by short rotation,and pretreatment technology of ethanol conversion has been formed.The main findings are as follows:?1?The phenotypic and lignocellulose chemical characters of black locust populations from nine places of origin were analyzed.It was found that there were significant differences among nine populations of black locust,and there was a significant positive correlation between cellulose content and leaf phenotypic characters.The population of Fei County from Shan Dong Province had the highest cellulose content which was 36.92%.According to cluster analysis and principal component analysis?PCA?based on phenotypic and lignocellulose chemical characters of black locust populaitons,which were divided into three groups.The population of Fei County from Shan Dong Province had the characteristic of high cellulose content.The results also showed that the clones from Fei County were suitable as feedstock of cellulose ethanol for silviculture.?2?According to principal components analysis of 218 black locust clones,the study constructed a selected system with lignocellulose characters as the main standard and phenotypic characters as the secondary standard.A total of 22 quality black locust clones were selected,whose average cellulose content increased by 5.71% and the average lignin content reduced by 18.27% compared with the original clones.These quality clones of black locust had widely geographical distribution.The results indicating that the quality black locust clones were suitable as feedstock of cellulose ethanol,and had a comprehensive development potential.?3?The results showed that the populations of Ping Quan from He Bei Province and Yan Qing from Beijing City had the highest level of genetic diversity,and there was a low degree of genetic differentiation among the seven populations of black locust with 14 pairs SSR primer.All of black locust populations were divided into three clusters based on the genetic distance by the unweighted pair group method using arithmetic average?UPGMA?and the Bayesian Mixed Model?Structure?,and there was no significant positive correlation between genetic differentiation and geographic distance among populations of black locust by Mantel-test.?4?Core collections of black locust were constructed by stepwise clustering,which contained 21 clones of black locust.There was no significant difference on genetic diversity between core collections and primary population,and no significant genetic diversity among the core collections of black locust.The evaluation showed that the core collections,which accounted for 12.37% of the primary population,covered genetic information at least 90%.The core collections of black locust were considered ideal.?5?By investigating the growth of two types in black locust short rotation sprouts,the results showed that the height,basal diameter and biomass of the sprouts was increasing,and the number of single branch was decreasing in 1-5 age after short rotation.The total biomass of black locust mainly based on sprouts from root in 1-2 age after short rotation,and the sprouts from stump became the main accumulation for total biomass in 3-5 age after short rotation.The total biomass per unit and mean annual total biomass of black locust sprouts respectively reached a maximum value of 21.36 t/hm² and 4.27t·a^-1·hm^-2 in 5 age after short rotation.Finally,in order to obtain more biomass,the sprouts of black locust should be harvested in 5 age after short rotation.?6?By determining the lignocellulose content of two types in black locust short rotation sprouts,the results showed that the content of cellulose and hemicellulose were increasing,and the lignin content without significant difference in 1-5 age after short rotation.The yield and content of cellulose in black locust sprouts from stump were higher than that from root.Therefore,black locust sprouts from stump was more suitable as feedstock for cellulose ethanol.The total biomass per unit and mean annual total biomass of cellulose reached a maximum value of 8.58t/hm²,1.72 t·a^-1·hm^-2 in 5 age after short rotation,respectively.In order to obtain more feedstock with high yield of cellulose,the sprouts of black locust should be harvested in 5 age after short rotation.?7?The cellulose content of black locust sprouts was significantly increased,and the content of hemicellulose and lignin were significantly reduced after pretreatment with steam explosion,and analysed with observation of morphological structure and fourier transform-infrared spectroscopy.The results showed that the steam explosion method could effectively deconstruct lignocellulose,and significantly increase the yield of cellulose.Different steam pressures could significantly increase cellulose content of black locust,and different incubation time could effectively reduce hemicellulose content.Steam pressure 2.5MPa and incubation time no less than 5min was the best technological conditions for the black locust sprous from stump,steam pressure 2.5MPa and incubation time in 8min was the best technological conditions for sprouts from root.Under above conditions,a better effect could be obtained by pretreatment with steam explosion.This study mainly based on the theory of tree genetics and breeding,and silviculture.Purpose of research was to provide theoretical basis and technical reference for obtaining more high cellulose content and quality feedstock of black locust,and effectively break the bottleneck of the shortage of black locust feedstock in cellulosic ethanol.Finally,this study laid a good foundation for the development of cellulosic ethanol which using black locust lignocellulose as feedstock.Selection of the high cellulose content and quality black locust clones,harvest black lcosut sprouting forest by short rotation and process condition of steam explosion pretreatment filled the gaps in the systematic research of black locust lignocellulosic energy feedstock forest in our study.At the same time,the interdisciplinary study which combining harvest sprouting forest by short rotation with pretreatment of steam explosion has opened up a new way for the development of black locust cellulosic ethanol.