Effects of Fusarium oxysporum f. sp. cubense on antioxidant capacity in roots of different resistant banana varieties

【Objective】 The change trends of antioxidant enzyme activities and antioxidant capacity in roots of different resistant banana varieties(Guijiao 9, Baodao and Nantianhuang) before and after Fusarium oxysporum f. sp. cubense race4(Foc4) infection were analyzed to lay a foundation for revealingthe resistance mechanism of different banana varieties on Fusarium wilt.【Method】 The different resistant banana varieties viz., Guijiao 6, Guijiao 9, Baodao, and Nantianhuang were inoculated with the Foc4 strain Foc37-GFP(spore suspension concentration 1.0×10⁶ CFU/mL) by using Foc37-GFP-solution culture method. The activities of superoxide dismutase(SOD), peroxidase(POD), catalase(CAT) and phenylalanine ammonialyase(PAL), superoxide anion(O₂^-·) clearancerate and antioxidant capacity in roots of different varieties were detected during 0-6 days of inoculation. 【Result】 After inoculatedby Foc37-GFP, the activities of SOD, POD, CAT and PAL in the roots of susceptible variety Guijiao 6 showed the change trend of increasing firstly and then decreasing;the POD, CAT and PAL activities were extremely lower than those of resistant varieties(P<0.01, the same below), while the SOD activity was extremely higher than other varieties on the 6^th days. Root O₂ clearance rate showed trend of rising, dropping and then rising, and reached the highest value on the 6^th days;the total antioxidant capacity did not change significantly at early stage(P>0.05), and was extremely lower than the three resistant banana varieties on the 6^th days. After Foc37-GFP infection, the activities of SOD, CAT and antioxidant capacity in root of Baodao banana decreased first, then increased and decreased rapidly;its POD activity increased first and then decreased, and PAL activity and O₂^-·scavenging rate showed a change trend of increasing, decreasing and increasing again. The change trend of SOD activity in roots of Nantianhuang was consistent with that of Baodao banana. On the whole, the activities of POD, CAT and PAL in rootof Nantianhuang increased first and then decreased. It found that O₂^-·scavenging rate increased with less change range, and total antioxidant capacity decreased first and then remained at a certain level. The activities of SOD, POD, PAL and O₂^-·scavenging rate of Guijiao 9 showed a change trend of first decreasing, increasing and decreasing;the activity of CAT decreased rapidly first and then increased rapidly, and reached the highest on the 6^th day, which was close to the activity level of Baodao, but significantly higher than those of Nantianhuang and Guijiao 6. The total antioxidant capacity showed a change trend of first increasing, decreasing and increasing, which was opposite to the changes of SOD, POD and PAL activities and O₂^-·scavenging rate, and also opposite to those of Baodao.【Conclusion】 The antioxidant enzymes in root of susceptible variety Guijiao 6 mainly play an antioxidant role in a synergistic way, while the antioxidant enzymes of resistant varieties Baodao, Nantianhuang and Guijiao 9 mainly play an antioxidant role through complementary ways. Different antioxidant enzymes in roots of different resistant banana varieties play different leading roles at different periods of Fusarium wilt infection, so as to maintain the dynamic balance of antioxidant enzyme system.