Relationship between Lignin Metabolism and Lodging Resistance in Wheat

Abstract

As a component of cell wall,lignin is believed to be relevant to mechanical intensity of culm.In this study,we investigated the dynamic changes of lignin content and activities of four enzymes involved in lignin metabolism in culm as well as the snapping resistance and lodging index of wheat(Tritcum aestivum L.) to disclose the relationship between lignin content and lodging resistance.The lignin content and activities of phenylalanine ammonia-lyase(PAL),tyrosine ammonia-lyase(TAL),cinnamyl alcohol dehydrogenase(CAD),and 4-coumarate:CoA ligase(4CL) were tested with the second internode of six cultivars with different lodging resistance.The snapping resistance and culm lodging index were determined at anthesis,milking,and maturity stages.The lignin content varied significantly among cultivars.Jimai 22 and Jimai 20,which showed high resistance to culm snapping and loging,had higher lignin content and the activities of PAL,TAL,CAD,and 4CL than other cultivars.The lignin content was negatively correlated with the actual lodging ratio(r = -0.83,P 0.05),and positively correlated with the snapping resistance of culm(r = 0.86,P 0.05).The activities of PAL,TAL,and CAD were positively correlated with lignin content with correlation coefficients of 0.78(P 0.05),0.77(P 0.05),and 0.85(P 0.05),respectively.Based on these results,we conclude that high activities of PAL and CAD are the enzymatic basis of increased lignin content,and the lignin content in culm can be used as an important indicator to evaluate lodging resistance of wheat.