| Banana(Musa spp.)is one of the most important fruit and food crops.Fusarium wilt caused by Fusarium oxysporum f.sp.cubense(Foc)is one of the most destructive diseases substantially reducing the production of banana in the world.So,study on the disease resistance mechanism can provide theoretical basis for the prevention of banana Fusarium wilt and disease resistance breeding.Digital gene expression(DGE)was widely employed to reveal the molecular mechanism of plant disease resistance.However,the detailed information of the differences in gene ontology(GO)items and Kyoto encyclopedia of genes and genomes(K EGG)pathways between resistant and susceptible banana cultivars was limited.In the present study,tissue-cultured plantlets of ‘Yueyoukang 1'(highly resistant to Fusarium oxysporum f.sp cubense race 4,Foc4)and ‘Baxijiao'(highly susceptible)(Musa spp.AAA)were used to reveal their differential responses to this pathogen using DGE technique by various bioinformatic tools including Venn diagram,GO annotation analysis and KEGG pathways analysis.Additional,with the development of breeding industry,NPVP(New Plant Varieties Protection)has become more and more important.DUS(Distinctness,Uniformity and Stablity)testing is a technological base of new varieties protection and the scientific proof for granting variety rights.In this study,the tests of DUS of three new cultivars/clones obtained by radiation mutagenesis were carried out using ‘Beidaijiao'(Musa spp.AAA)as the control,so as to lay the foundation for cultivating new varieties of banana with good traits.Disease resistance was investigated on two clones(HNAJ0106 and HNAJ0219)using ‘Baxijiao' and ‘Yueyoukang 1'(Musa spp.AAA),highly susceptible and resistant to the Foc 4 respectively as the controls.The main results obtained are showed as follows: 1.DGE analysis(1)The amount of genes with Reads per kilobase of transcript per million mapped reads at 3-15 was the most.The ratio of these genes to total genes was about 37%.(2)A total of 955 differential expressed genes(DEGs)were observed among these two cultivars,‘Baxijiao'(highly susceptible)and ‘Yueyoukang 1'(highly resistant),with 575 up-regulated and 380 down-regulated genes.Thirty-two and 193 DEGs were found in the resistant and the susceptible cultivars after pathogen attack compared to control.We found 502 and 228 DEGs between these two cultivars berore and after pathogen inoculation,respectively.Genes differentially regulated after pathogen infection were annotated by 17 GO items in the resistant cultivar and by 99 GO items in the susceptible one.Two hundred and twenty-three and 122 GO items were found before and after the inoculation.DEGs found in the resistant and susceptible cultivar were classified into 14 and 51 K EGG pathways respectively.Sixty-seven and 47 KEGG pathways were found to be accumulated between these two cultivars before and after pathogen inoculation respectively.(3)Venn diagram was used to analyse the realationship between the disease resistance and the differentially expressed genes,the enriched GO terms and KEGG pathways.The results showed that: 26 genes,sush as LOC103985110 and LOC103977596,were up-regulated exclusively in inoculated susceptible cultivar compared to control,suggesting they were possibly responsible for the susceptibility of bana na to Foc4.Similarly,LOC103977837,LOC103973892 and othe 9 genes were possibly responsible for the constitutive susceptibility.On the other hand,33 genes,such as LOC103993913,LOC103991268,were possibly responsible for the constitutive resistance.Twelve genes up-regulated exclusively in inoculated resistant cultivar compared to the control but not in the susceptible one(such as LOC103978674 and LOC104000780)might be responsible for the induced resistance.Probable WRKY transcription factor 50 is the only one gene possibly responsible for both of the constitutive and induced resistance,suggesting the most important role of this gene in the resistance.Fouty-five GO items,such as GO :0006882,GO :0006816 and GO :0010181,found exclusively between BXCK and BXT were possibly involved the susceptibility.On the contrary,9 GO itmes(e.g.GO :0006882,GO :0006816 and GO :0004089)were possibly involved in the resistance.There were 39 GO items appeared only in two pairs of comparison(between two cultivars before and after inoculation),which possibly responsible for the constitutive resistance/susceptibility.Six KEGG pathways(fructose and mannose metabolism,sphingolipid metabolism,butanoate metabolism,porphyrin and chlorophyll metabolism,carotenoid biosynthesis and riboso)exclusively appeared in inoculated susceptibe cultivar,suggesting they were possibly involved in the susceptibility.O ne KEGG pathway,namely protein export,were exclusively present in the inoculated cultivars and possibly involved in the induced resistance.There were 10 KEGG pathways,such as citrate cycle and steroid biosynthesis,present only in two pairs of comparison(between two cultivars before and after inoculation),indicating that they were possibly involved in the constitutive resistance/susceptibility.2.The main results of DUS test(1)The leaf length and petiole length of HNAJ0212 were significantly larger than those of the control culitvar.On the contrary,the width of the finger and the width of the fruit were significantly smaller than those of the control.The fruit length of HNAJ0325 and 'Huanong aijiao 1' was significantly longer than that of the control.(2)The ear length of the three cultivars/clones was significantly longer than that of the control cultivar.The length of the ‘Huanong Aijiao 1'was almost twice as long as that of the control.Furthermore,‘Huanong Aijiao 1'showed good uniformity and stability,and it has been obtained the authorization of NPVP.3.Identification of disease resistanceAfter 28 days of inoculation,the susceptible cultivar showed the highest disease index(0.91),while the resistant cultivar showed the lowest one(0.72).The disease index of HNAJ0106 and HNAJ0219 was in the middle. |
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