Study On Predominant Characteristics Of Different Species Of Autotetraploid Paulownia Plants

Abstract Paulownia is an important fast-growning,high quality timber and greening tree species,but the serious problems such as withces’ broom,large crown and short trunk have not been solved.Polyploid have more extensive adaptability and stress resistance.In order to breed new varieties of Paulownia plants and solve the problems in the Paulownia production,study on biological characteristics,stress resistance,photosynthetic characteristics and genetic variations between tetraploid Paulownia tomentosa(PT4),tetraploid Paulownia fortunei(PF4),tetraploid Paulownia australis(PA4),tetraploid Paulownia tomentosa × Paulownia fortunei(PTF4),tetraploid Paulownia elongate(PE4)and their diploid Paulownia(PT2,PF2,PA2,PTF2 and PE2).The main results were summarized as follows:(1)There were 1-7 days of phenological time variations between tetraploid Paulownia and its diploid.Compared to diploid Paulownia,tetraploid Paulownia had larger thickness of upper and lower epidermis,palisade tissue,cell tense ratio and ratio of thickness of palisade tissue to thickness of sponge tissue,but spongy ratio and thickness of spongy were the opposite.The length and width,size,ratio on polar axis to equator axix,pollen deformity rate and 1000-grain weight of tetraploid Paulownia were higher than those of diploid Paulownia,but germination rate of seed of tetraploid Paulownia was lower than that of diploid Paulownia.(2)The cold resistance,drought resistance and salt resistance of the tetraploid Paulownia were stronger than those of the diploid.The ranges of eight physiological indexes of five tetraploid Paulownia and their comsponding diploid Paulownia plants were studied in cold stress.The cold resistance order was PT4>PTF4>PF4>PE4>PT2>PA4>PE2>PTF2>PF2>PA2 by subordinate function.The salt resistance of tetraploid Paulownia was evaluated by subordinate function based on the physiological indexes the water and chlorophyll contents of the leaves,the relative conductivity and content of MDA,the SOD activity and content of soluble protein,the content of soluble sugar and proline and salt resistance in the soil with 0.6%NaCl.The salt resistance order was PTF4>PT4>PF4>PTF2>PT2>PA4>PF2>PA2.The drought stress tolerance order was PT4>PTF4>PA4>PF4>PT2>PTF2>PA2>PF2 based on eight physiological indexes of leaves in the soil with 25%content of relative soil water by subordinate function.(3)The changing tendency of photosynthetic diurnal curves of tetraploid Paulownia was consistent with diploid Paulownia.The net photosynthetic rate and chlorophyll content of tetraploid Paulownia were higher than those of diploid different months.The diurnal variation of net photosynthetic rate of tetraploid Paulownia and diploid Paulownia were single peak curve in May,July,September and October,but those were bimodality in June and August,there was an obvious phenomenon of midday depression on photosynthesis.(4)There were no variation of DNA base sequences were amplified by AFLP.The DNA methylation patterns and level of tetraploid Paulownia were higher than those of diploid.The identical DNA fragments and size were amplified by the same primer and each pair primer amplified 50 to 70 bands between tetraploid and its diploid Paulownia by AFLP.The global DNA methylation level and hemi-methylation level of tetraploid Paulownia were higher than its diploid,and the DNA demethylation frequency was higher than DNA methylation.(5)The wood characteristics of tetraploid Paulownia were better than those of diploid.the fiber length,fiber length/width,basic density and white of wood of PTF4 were higher than those of diploid,but wood fiber wall thickness of tetraploid Paulownia were lower than their diploid.The wood physical-mechanical properties of PF4 were better than those diploid.The cold water extracts,hot water extracts,1%NaOH extracts and lignin of wood of PTF4 were lower than its diploid,but cellulose of wood was higher than those of diploid.(6)Transcriptome of leaves tissue of diploid and tetraploid Paulownia tomentosa was sequenced by next generation sequencing platform Illumina/Solexa.A large number of reads were generated and assembled into 43 588 transcripts with a complete open reading frame.Functional annotations of the complete transcripts were performed using public protein database NCBI nr,Pfam,KOG and KEGG.2 832 differentially expressed transcripts were screened out using EBseq software,after transcript expression levels were calculated by the FPKM method.458 difference transcripts were significant between tetraploid Paulownia tomentosa and its diploid.These transcripts are mainly concentrated in photosynthesis signal transduction,signal transduction,stress resistance,energy metabolism,and etc.14 transcripts were picked out for qRT-PCR validation,which results consistent with transcriptome sequencing.