Disease Resistant Evaluation For Three Groups Of Rubber Tree F₁ Hybrids From Cross Breedings And Cloning Of Germin-like Protein Coding Gene

Rubber tree(Hevea brasiliensis)is an important economic crops and strategical resource in tropical China.For nearly 30 years,corynespora leaf fall disease caused by Corynespora cassiicola which leads to huge loss of dry rubber yields is one of the most serious leaf diseases in rubber production.While resistant cultivars is the most effective control measure to the disease,we evaluated corynespora leaf fall disease resistance ability of three groups of hybrids from cross breedings,and cloned a disease-resistance related gene.The main research results are as follow:With method of mycelium inoculation in vitro,three groups of F1 hybrids(totals to 821 germplasms)from cross breedings using Yunyan 277-5 x IAN873,Yunyan 277-5 x Reken 525 and RRIC 103 x Reyan 8-79,were evaluated for their resistance to corynespora leaf fall disease using cas5 toxin-subtype of Corynespora cassiicola.60 germplasms with disease tolerance(resistance)were selected.Next,using the methods of mycelium inoculation in vitro and wilding toxin assay,the group of F1 hybrids from cross combinations using RRIC 103 x Reyan 8-79,which conforms to normal distribution,were re-evaluated with cas5,cas2 and casO toxin-subtypes of Corynespora cassiicola,and obtained 4 disease resistance germplasms.Also,expression level of 16 transcript-derived fragments(TDFs)acquired by cDNA-AFLP analysis were tested,and expression of TDF-FI7321 was related to disease resistance.Blast with the whole genome sequence information of rubber tree,we got one germin like protein(GLPs)gene,the genbank accession number is KT355593.with TDF-FI7321 sequence,and we also cloned this gene from The length of its cDNA is 696 nt,which encodes a 231-amino acids-long sequence.This sequence has 2 exons and 1 intron,and protein encoded by it has a conservativeβ-barrel structure which makes the gene to be one member of cupin superfamily.qRT-PCR analysis showed that the expressions level of HbGLP01 in resistant germplasms(including F1 hybrids)was significantly higher than that of susceptible germplasm(including F1 hybrids),Moreover,HbGLP01 expression was induced and significantly uprised by 3 toxin-subtypes of Corynespora cassiicola.Analysis of antioxidant enzymes activity showed that,the enzyme activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)were quite different in disease resistant and susceptible F1 hybrids,during inoculation with b Corynespora cassiicola.In disease-resistant F1 hybrid,SOD and POD enzyme activity raised at the first and then declined,SOD activity rapidly increased to the top when maintained for 24 hours,POD activity reached to the maximum when maintained for 12 hours,the CAT enzyme activity performance is relatively stable.In disease-susceptible F1 hybrid,the activity of SOD has was significantly lower than disease-resistnt hybrid,the activity of POD raised a little,and reached to the small peak when inoculated for 24 hours,the activity of CAT has basically no change.