Study On The Growth Promoting Effect Of Trichoderma Ghanense On Populus Davidiana×p.bolleana And Its Transcriptome Construction

Trichoderma spp.is an important and widely distributed biocontrol fungus.Many studies have shown that it has a good biocontrol effect on a variety of plant diseases and can promote plant growth.In this study,Trichoderma ghanense was used as the research object,and the tissue culture transplanted seedlings of Populus davidiana×P.bolleana were used as experimental materials to preliminarily explore the growth-promoting effect of T.ghanense on P.davidiana×P.bolleana seedlings.On this basis,the transcriptomes of T.ghanense strains under different induction conditions were constructed,and the biocontrol-related genes in the transcriptomes were screened and quantitatively analyzed.The main findings are as follows:Different concentrations of T.ghanense conidia suspensions（1.5×10³,1.5×10⁵and 1.5×10⁷cfu/m L）were used to irrigate the root circumference of the poplar seedlings in the amount,net photosynthesis intensity and chlorophyll content in leaves were compared.The control group was the tissue culture transplanted seedlings of the poplar seedlings only irrigated with tap water.The experimental results showed that the stem,root length,number of leaves,fresh weight and dry weight of the poplar seedlings in T2 and T3 treatments were significantly higher than those in the control group,and the average plant height increased by52.16%and 63.99%,respectively,at 60 days of treatment.At the same time,the contents of chlorophyll a,chlorophyll b and chlorophyll（a+b）in the leaves of the treatment group were significantly higher than those of the control group（P<0.05）.Both increased first and then decreased,showing a unimodal curve,and reached a peak at 12:00 noon,and the net photosynthetic rate（Pn）,transpiration rate（E）,stomatal conductance（Gs）and intercellular CO₂（Ci）was significantly higher than the control group（P<0.05）.The results showed that T.ghanense could promote the growth of the poplar seedlings and effectively improve the net photosynthesis intensity（Pn）of the poplar seedlings leaves,and the T2 and T3 groups had the best growth promotion effect.In order to preliminarily study the effect of T.ghanense on the resistance of the poplar seedlings,the suspended roots of different spores of T.ghanense were applied to the transplanted seedlings of poplar,and then at 0 h,1 h,3 h,6 h,12 h,1 d,5 d,10 d,15 d,and determination of the activities of four defense enzymes including phenylalanine ammonia lyase（PAL）,peroxidase（POD）,catalase（CAT）and superoxide dismutase（SOD）in the leaves of the poplar seedlings and the changes in proline and soluble protein content.The experimental results showed that,compared with the control group,T.ghanense could increase the activities of four defense enzymes and the content of proline（PRO）in the leaves of the transplanted seedlings of poplar.These results preliminarily indicated that T.ghanense could effectively improve the defense enzyme activity of P.davidiana×P.bolleana,thereby improving plant resistance,and had a great potential for biocontrol.By constructing the transcriptome of T.ghanense mycelium induced and cultured in 8induction media,a total of 2.48 Gb of data was obtained,and a total of 30 312 Unigenes were obtained through a series of splicing,assembly and de-redundancy,The non-redundant Unigenes obtained by sequencing were compared with the COG database to predict and classify their functions.These Unigenes are grouped into 25 functional categories.According to GO annotation and functional classification statistics,a total of 14 591 Unigenes were classified into 38 sub-categories in 3 categories.In the KEGG metabolic pathway enrichment analysis,a total of 9 715 Unigenes were annotated into 158 Pathways,and most of these Unigenes were involved in metabolic pathways and biosynthesis of secondary metabolites,starch and sucrose metabolism,etc.Screening the transcriptome data of T.ghanense strain,three types of biocontrol related genes were obtained:10 genes related to Trichoderma competition,298 genes related to hyperparasitism mechanism,and 37 genes related to antibacterial mechanism,a total of 345 genes.These research results lay a solid foundation for further research on the biocontrol mechanism of T.ghanense,development of genes related to biocontrol functions,and development of biological agents.In addition,real-time quantitative RT-q PCR technology was used to study 14 biocontrol genes under 9 different culture conditions（MM,C starvation,N starvation,1%leaf or stem powder of Shanxin poplar,expression patterns of the cell wall of poplar blight or poplar bark rot pathogens,5%poplar leaf blight or the fermentation broth of poplar bark rot pathogens）.The results showed that their expression changed significantly under different induction conditions,suggesting that they are involved in the recognition between T.ghanense and plants or phytopathogenic fungi,and may be involved in the response of T.ghanense to phytopathogenic fungi and P.davidiana×P.bolleana play a role in it.