The Molecular Response Of Induced Disease Resistance And Heat Tolerance Of Creeping Bentgrass Activated By 2,3-butanediol

Bacterial volatile compounds(BVC)produced by plant growth promoting rhizobacteria(PGPR)can promote plant growth directly or indirectly.Synthetic BVC analogue,such as 2,3-butanediol(BD),can also induce some plant resistance to pathogens.The present research used synthetic BVC analogue 2,3-butanediol to activate the disease resistance of creeping bantgrass seedlings or mature turf to against turfgrass brown patch.Transcriptome changes of creeping bentgrass inoculated with R.solani or treated with BD,and the hormonal level changes after inoculation or treatment were examined by RNA-seq or high performance liquid chromatography(HPLC).Furthermore,induced abiotic stress tolerance of creeping bentgrass and the molecular mechanism of creeping bentgrass induced heat tolerance is discussed in this research.The following results are obtained.(1)BD has no direct effect on pathogen growth,while it can activate induced systemic resistance(ISR)of creeping bentgrass to against R.solani.BD at 250 ?M was the most suitable concentration for resistance activation in lab grown seedlings.It reduced disease by almost 70% on foliar lesions.BD at 550 ?M was best for resistance activation in field turf,and effectively suppressed symptoms by almost 60%.(2)Disease resistance of CB caused by pathogen and resistance induced by 2,3-BD is different at transcriptomic level.The difference can be detected on transcription factors(TFs),the most enriched differential expressed TFs were C2H2 and C3 H zinc-finger TFs families for the former,while bHLH,C2C2-CO and NAC families for the latter.Both of the two kinds of resistance can lead to up-reulation of R-genes.The most variation families of former were genes related with NBS-LRR containing resistance protein,LRR-like receptor protein kinase,ABC-2 type transporter,U-box domain containing protein kinase,and heat shock protein family.For the latter resistance were only NBS-LRR containing resistance protein and LRR-like receptor protein kinase related genes the most abundant.Several up-regulated DEGs were enriched in pathogen recognition,ROS eliminate,signaling transport,programmed cell death,pathogenesis-related protein and so on for pathogen induced disease resistance,while BD induced ISR process can promote expression of JA signal related gene and pathogen-related gene 5.The expression level of randomly selected DEGs was tested with qRT-PCR,and they were consistent with the results of RNA-seq analysis.(3)The amount of zeatin(ZT)was lower in infected plants than in healthy plants at initial stages of infection.At 10 days afer inoculation,ZT increased significantly more in infected plants than in healthy plants.But plants treated with BD had less ZT than plants treated with water after inoculation.The ABA content was unstable during growth stages.Whether or not treated with BD,the ABA content increased with the inoculation time,while the increase after water treatment was more dramatic than those treated with BD.The IAA content of inoculated plants was lower than healthy plants,and BD treated plants had more IAA than water treatment with later inoculation.(4)Under drought stress,salinity stress,low temperature and freezing stress,BD treatment had no significant and sustaining effect on creeping bantgrass tolerance.However,BD treatment can significantly enhance tolerance of creeping bentgrass toward heat stress,and 300 ?M showed the most obvious effect.The turf quality,plant growth rate,chlorophyll content,Fv/Fm and cell membrane stability were measured to confirm the differential effects of BD on heat tolerance of PennA4 and Penncross cultivars.The expression of genes related with creeping bentgrass growth,metabolism and stress protection were measured.The results showed that during high temperature stress,most of the genes showed short-term(7 days)time response to BD treatment,and also long-term(30 days)time responses for PennA4.But for Penn Cross,instead of the whole time up-regulation,some of the genes showed short term response,while some showed long term response to BD treatment.In conclusion,with pathogen inoculation or under heat stress,BD treatment can promote plant growth,regulate multiple gene expression and endogenous hormone secretion.So it can effectively enhance the response ability for helping plant to defend pathogen attack and heat stress.