Bt抗虫棉早衰:认识演变、发生机制与防控技术OA

Since its commercial release in China in 1997,transgenic Bacillus thuringiensis(Bt)cotton has fundamentally improved the control of cotton bollworm,markedly reduced chemical insecticide use,and profoundly reshaped cotton production practices in the country.However,during the initial phase of adoption,premature senescence,characterized by mid-to late-season leaf yellowing,reddening,scorching,abscission,and root functional decline,emerged as a conspicuous problem in some Bt cultivars and was initially misattributed to a direct negative effect of Bt gene insertion or constitutive Bt protein expression.More than two decades of research and field practice have made it clear that premature senescence in Bt cotton is neither a direct consequence of Bt gene insertion or Bt protein expression itself nor an inherent attribute of Bt cotton.Rather,it is a maturity imbalance driven by source-sink imbalance,root-shoot uncoupling,insufficient nutrient supply,environmental adversity,and disease pressure under specific genetic backgrounds and heavy boll load.Its physiological basis includes the photosynthetic function decline,chlorophyll degradation,reactive oxygen species accumulation,membrane lipid peroxidation,imbalanced mineral nutrient uptake and remobilization,reduced root activity,decreased cytokinin level,and enhanced abscisic acid,jasmonic acid,and ethylene signaling.At the molecular level,premature senescence involves changes in sugar transport and metabolism,hormonal signaling,reactive oxygen species-associated oxidative regulation,and the structural and functional deterioration of chloroplasts,along with senescence-related transcription factors and genes networks that coordinate chlorophyll degradation and nutrient remobilization.Systematic studies by several research groups in China have contributed to an integrated management framework involving maturity-stable cultivars,rational plant density,optimized sowing date,coordinated nitrogen and potassium supply,precise late-season nitrogen management,chemical regulation,root promotion and leaf protection,moderate sink reduction,disease resistance/tolerance,and harvest-aid coordination.This review summarizes the research trajectory of premature senescence in Bt cotton from initial controversy and conceptual correction to mechanistic integration and technical control,with emphasis on the evolution of understanding,key evidence chain,representative research progress,molecular regulatory network,integrated management strategies,and unresolved issues.