The effect of Xanthomonas citri subsp.citri infection on physiological indicators and antioxidant enzymes in Hainan green sweet orange
Analysis of the impact of Xanthomonas citri subsp.citri(Xcc)infection on the growth metabolism and antioxidant enzyme system of Hainan green sweet orange(Citrus sinensis L.)can significantly enhance the understanding of its regulatory mechanisms under pathogen stress and promote the breeding of resistant varieties.The physiological metabolic changes and the response of key antioxidant enzymes of Hainan green sweet orange under Xcc infection were studied by pot experiment.The results showed that the plant height growth and leaf area of green sweet orange plants were not significantly affected by Xcc infection treatment,but the fresh weight were significantly decreased.Moreover,Xcc infection caused yellowing of green sweet orange leaves,in which the proportion of decrease in the content of chlorophyll a,chlorophyll b reached 74.09％and 81.75％.During 0～72 h of Xcc infection,the activity of superoxide dismutase(SOD),phenylalanine ammonialyase(PAL)and the content of malondialdehyde(MDA)in green sweet orange leaves reached the peak value at 24 h,which was 6.15,5.08 and 5.60 times of that before Xcc infection,respectively,and the above index values were higher than that of blank control.The redundancy analysis(RDA)showed that the amount of enzyme activity changes and the physiological indexes maintained a better negative correlation.In conclusion,Xcc infection mainly caused a decrease in photosynthetic pigment content of green sweet orange leaves,which affected the photosynthetic metabolism of leaves,SOD and PAL are the key antioxidant enzymes in green sweet orange plants to respond to the infestation by Xcc.The results of this study will provide a theoretical research basis for directional selection in breeding for citrus resistance in Hainan.
green sweet orangeXanthomonas citri subsp.citri(Xcc)physiological indicatorsphotosynthetic pigmentsantioxidant enzymes
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