Study On Seedling Screening And Tissue Culture Technology Of Phoebe Zhennan In Guizhou

Phoebe zhennan（nanmu）is a large subtropical evergreen tree belonging to（Lauraceae）Phoebe,Nanmu is also called Zhennan.Nanmu is a unique landscaping tree species and precious timber species in China.Its material is good known as"gold in wood",with high economic value and ornamental value.In China,nanmu is mainly distributed in the northwest of Guizhou,west of Hubei,Sichuan and Chongqing.Due to the long-term excessive cutting,slow growth and artificial cultivation technology is not perfect of nanmu,the resources of nanmu have been seriously damaged.It is an effective means for resource protection and breeding of nanmu to develop excellent germplasm screening and tissue culture rapid propagation technology.In this study,we collected 48 nanmu seeds from 11 main distribution areas of Guizhou province.The seed characteristics and germination status were observed,and the superior individual were screened preliminarily through the determination of the progeny and seedling stage.The descending segment with axillary buds was used as explants,adventitious bud induction and rooting culture were carried out,the optimum tissue culture conditions of nanmu were selected.This study provided some technical support for nanmu germplasm resource protection,breeding and breeding technology The main research results of this paper are as follows:1.Analysis of seed characteristics and germination rate of nanmu from different provenancesBy analyzing the differences of 1000-grain weight,longitudinal diameter and transverse longitude among 48 single plant,1000-seed weight（83.1～557.9g）,longitudinal diameter（9.94～16.17mm）,transverse diameter（6.23～9.27mm）,fruit shape index（1.42～2.02）of seeds from single plant.SQ20-06 showed absolute superiority in the average 1000-grain weight,longitudinal diameter and transverse longitude of nanmu seeds in 48 families.SQ20-22 and MT20-01 showed relative advantages in the average 1000-grain weight,longitudinal diameter and transverse longitude of nannan seeds in 48 single plant.The results showed that there were significant differences in germination rate of nannan between different single plant by hydroponics and soil culture under artificial climate chamber and by drill sowing under natural conditions.Under the condition of artificial climate chamber,After 60days,the germination number of seeds was counted.the seed germination rate of hydroponic culture was the highest,and the seed germination rate of different families ranged from 50.84%to 94.54%,with an average germination rate of 80.89%.2.Analysis of multi-embryo characteristics of nanmu single plantMultiple embryos were observed during the germination of nanmu seeds,and the frequency was as follows:single embryo ratio>double embryo ratio>triple embryo ratio.The ratio of single embryo,double embryo and triple embryo were 21.67%～67.67%,4.67%～37.67%and 0～18.54%respectively.There were no significant differences in seedling height and ground diameter between single embryo seedling（D）and large double-embryonic seedling（SD）,but significant differences in seedling height and ground diameter between small double-embryonic seedlings（SX）.The net photosynthetic rate（P_n）,stomatal conductance（G_s）,intercellular CO₂ concentration（C_i）and transpiration rate（T_r）of D were the main advantages in photosynthesis compared with that of SD and SX.The results showed that the P_n,G_s,C_i and T_r of D were 1.22,1.44,1.78 and 1.42 times higher than those of SX,respectively.The P_n,G_s,C_i,T_r of SD were 1.14,1.31,1.23 and 1.27 times of those of SX,respectively.This analysis of photosynthetic parameters shows that D and SD were dominant,while SX inferior.3.Analysis of growth rhythm and biomass of nanmu single plant from different provenances at seedling stageThe growth rhythm and biomass accumulation of different nanmu families at seedling stage were analyzed.The growth period of seedling height and leaf was from July to August,and the growth period of ground diameter was from August to September.The biomass of 1-year-old nanmu seedlings was significantly different among different families,ranging from 0.97 to 3.82g,and the highest was the JK20-08 family,up to 3.82g.JK20-06,SQ20-06,JK20-08,WC20-05 and SN20-11were selected as excellent families according to 10%selection rate by comprehensive evaluation of plant height,ground diameter and biomass at 1-year seedling stage.The photosynthetic parameters of JK20-06,SQ20-06 and JK20-08 superior families were analyzed.The P_n,G_s,C_i and T_r of JK20-06 were 1.30,1.47,1.14 and 1.45 times of those of SQ20-06,respectively.The P_n,G_s,C_i and T_r of SQ20-06 were 1.02,1.03,1.30 and 1.02 times of those of JK20-08,respectively.The photosynthetic parameters JK20-06>SQ20-06>JK20-08 were consistent with the growth characteristics.4.Study on tissue culture and rapid propagation of NanmuThe optimal combination treatment conditions for seeds was 75%C₂H₆O 2 min+0.1%Hg Cl₂ 18 min.The survival rate was 85.00%,the contamination rate was 6.11%,and the mortality rate was 8.89%.The germination rate was 92.00%in MS+2.0 mg/L GA₃ culture medium.The stem segments with axillary buds were inoculated on bud induction medium（MS+2.0 mg/L6-BA+0.01 mg/L IBA）,and the average number of induction was 1.88.In 1/2MS culture medium,when IBA concentration was 1 mg/L,the rooting rate reached 56.30%.