Difference Of Resistance Analysis Among Banana Varieties Infected By Fusarium Oxysporum F.sp.cubense 4

Musa spp.is an important fruit grown in the tropics and subtropics and is the second largest fruit crop in the world.Banana Fusarium Wilt caused by Fusarium oxysporum f.sp.cubense(Foc)is the most harmful disease to the global banana planting industry.There is currently no effective chemical agent to control this disease.Maybe breeding and planting disease-resistant varieties is the most economical and effective way to prevent this disease.However,there is currently no report on the systematic resistance evaluation of new banana varieties selected in China in recent years.This paper carried out the first determination of resistance to Foc4 based on the collection of 8 banana varieties newly selected in China.We analyzed the differences between resistant variety‘Zhongjiaojiuhao’and susceptible variety‘Brazilian’when infected by pathogen and analysis the pathogeniccontents in soil and plants.Next,we determinated the resistance to polygalacturonase and changes in hydrogen peroxide and flavonoid content in plants.Finally,we analyzed the enzyme activities of PAL(phenylalanine ammonia lyase),POD(peroxidase),PPO(polyphenol oxidas)and SOD(superoxide dismutase)Related to disease resistance.Major research results were as follow:1.Among the tested varieties,we don’t find immunity one.Banana disease index increased when pathogen spores concentration increased.‘Zhongjiaojiuhao’and‘Zhongreyihao’is highly resistance,‘Nantianhuang’is medium to strong resistance,‘Zhongjiaoerhao’and‘Guijiaokangerhao’is medium resistance,‘Zhongjiaosanhao’and‘Guijiaokangbahao’is highly sensitive when set‘Brazilian’infected by Foc4 as a highly sensitive reference.‘Zhongjiaojiuhao’is most resistance one in all tested banana.2.All of‘dwarf banana’withered when infected by Foc1 in all biomass concentration(10~4spores/m L to 10~6spores/m L).Although‘Zhongjiaojiuhao’bulb was browned at high spore concentrations,the plants did not appear wilting and showed strong disease resistanceendure.3.The dynamic changes of Foc4 in ‘Zhongjiaojiuhao’ and ‘Brazilian’ plants was detected by q PCR technique every 7 days after infection.The pathogen copies of Foc4 in roots,bulbs and pseudostem of‘Zhongjiaojiuhao’were lower than‘Brazilian’.The pathogencopies of Foc4 in plants is positively correlated with plant disease sensitive.4.We used laser scanning confocal microscope too bserve the difference between Foc4infects differentdisease-resistant banana varieties.We found that:Foc4 infects‘Brazilian’faster than infects‘Zhongjiaojiuhao’,and the content of pathogens in vascular bundles and bulbs are higher,too.Foc4 in the‘Zhongjiaojiuhao’can’t infect pseudostem,but can infect the‘Brazilian’pseudostem and other parts.No pathogen infection was observed in the newborn root of‘Zhongjiaojiuhao’,but the newborn root of‘Brazil Banana’was infected like the older root.‘Zhongjiaojiuhao’is significantly more resistant to polygalacturonase than’Brazilian banana’.This indicates that there are differences in cell wall structure between the two varieties.5.The defense response of two varieties can be induced after inoculation of Foc4.‘Zhongjiaojiuhao’showed 2 peaks in hydrogen peroxide after Foc4 infection,while‘Brazil banana’had only one peak.The increase of flavonoid content in‘Zhongjiaojiuhao’was also significantly stronger than in‘Brazilian’.We found that four disease-resistant enzymes of PAL,POD,PPO and SOD in‘Zhongjiaojiuhao’that these defensive enzyme activities increase rapidly,have high activity,and last for a long time when infected by Foc4.