丝黑穗病菌侵染对转Bt基因玉米抗病性相关指标的影响

Influence of infection with head smut fungus(Sphacelotheca reiliana(Kühn)Clint.)on disease related index of transgenic Bt maize

为明确外源Bt基因的导入对玉米抗病性的影响,本研究以转Bt基因玉米株系和其受体亲本郑58为材料,比较了接种丝黑穗病菌(Sphacelotheca reiliana(Kühn)Clint.)后转Bt基因玉米防御酶系统、激素水平及次生代谢的变化情况,探讨了转Bt基因玉米对病害抗性的相关生理机制。研究结果表明:接种丝黑穗病菌后,转Bt基因玉米在吐丝期的发病率达到24%,单穗总粒重较对照下降18%,百粒重下降12%,而郑58发病率为15%,产量与对照无显著差异。转Bt基因玉米的超氧化物歧化酶(SOD),过氧化物酶(POD),过氧化氢酶(CAT)等防御酶活性比郑58玉米在抵御病害侵染时表现的较弱,丙二醛(MDA)含量显著增加,膜脂过氧化程度较为严重,这可能是造成转Bt基因玉米产量下降明显的原因之一。生育前期生长素(IAA)、赤霉素(GA)、玉米素核苷(ZR)含量明显下降,而脱落酸(ABA)含量明显升高使得转Bt基因玉米生长受限,同样造成产量的显著下降。此外,在各个生育时期体内的单宁和总酚的含量都低于其受体郑58玉米,生化防御机制受限也可能造成抗病性的降低,进而产量下降。

In order to clarify the influence of exogenous Bt gene on edipemics of maize disease,transgenic Bt maize and its'receptor Zheng 58were used for comparing the occurrence of corn disease at different development stages under field condition and under a condition which infected by head smut fungus.Influence of the disease on defense enzymes system,hormone level and secondary metabolites were studied.Results showed that incidence of disease reached 24% at silk stage of transgenic Bt maize infected by head smut fungus,total grain weight of single spike decreased 18%to control and hundred-grain weight of the seed decreased 12%,whereas incidence of disease was 15% and no significant difference of production with related control.Detection of physiological and biochemical index showed that defense enzymes of Bt maize,such as superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),enhanced slower than those of Zheng 58and the activities were weaker than Zheng 58.The malondialdehyde(MDA)content of Bt maize enhanced significantly indicated that membrane lipid peroxidation was more severely. Lower protective enzyme activities and more severe membrane lipid peroxidation might inhibit the growth of Bt corn, which might be one of the causes for yield reduction.Remarkable decrease of concentration of auxin(IAA),gibberellin(GA),zeatin riboside(ZR)and increase of abscisic acid(ABA)under fungus treatment inhibited the growth of Btmaize.Moreover,the fact that sharp decline of condensed tannins and total phenolics concentration in Bt maize(significantly higher than its receptor Zheng 58)in every growth stages suggested that inhibited biochemical defense mechanism influenced the incidence of disease and final maize production.