Relationship between root activity， root physical structure of banana and resistances to fusarium wilt

【Objective】This paper explored the differences of root activity and root microstructure among different banana varieties and their relationship with the resistance to fusarium wilt，so as to provide theoretical basis for the evaluation of banana resistance to fusarium wilt.【Method】The tissue culture cup seedlings of 12 banana varieties（strains）were used as experimental materials. Through the inoculation treatment on wound root，the situations of bananas after inoculation of Fusarium oxysporum f. sp. cubense race 4 （Foc4）were analyzed， and the resistance levels of different banana varieties（strains）to physiological race 4 of fusarium wilt were evaluated. The difference of root tissue structure of different banana varieties and root activity indexes under the conditions of Foc4 inoculation were compared and analyzed by microscopic observation and physical and chemical analysis. Correlation between root activity as well as anatomical structure and disease occurrence was studied by single factor variance analysis and Duncan significance analysis.【Result】Among the banana varieties（strains）tested，6 banana varieties（Baodao banana， 175b， ZR1， 23b， MJ9， 43b）were medium resistant， 4 banana varieties （79b， 169b， 265b， 264b）were susceptible， and 2 banana varieties （173b， Guijiao No.6）were highly susceptible. On day 40 after inoculation，the root activity of all banana varieties increased. The increase range of Baodao banana was 701.00%. The root activity of resistant varieties （strains）was significantly higher than that of susceptible varieties（strains） （P＜0.05，the same below）. Compared with Guijiao No.6，Baodao banana significantly increased 674.24%. Compared with susceptible varieties （strains）， resistant varieties （strains）had more vessel number， smaller vessel diameter， more parenchyma cells，and thicker vessel cell wall. Compared with Guijiao No.6，vessel number，vessel diameter， parenchyma cell number and vessel cell wall thickness of Baodao banana significantly increased by 106.98%，decreased by 50.20%，increased by 65.07%，and increased by 63.51% respectively. Root activity，vessel number，parenchyma cell number and vessel cell wall thickness were significantly or extremely significantly negatively correlated with disease severity （P＜0.01，the same below），while vessel diameter was significantly or extremely significantly positively correlated with disease severity.【Conclusion】Root activity，vessel number in root xylem，vessel diameter，parenchyma cell number and vessel cell wall thickness are strongly related to the disease resistance of banana varieties（strains）. Root activity and anatomical structure can serve as indicators to screen resistant varieties of fusarium wilt at the seedling stage of banana.