糜子叶片防御酶系及抗氧化物质对黑穗病菌胁迫的响应

摘要

Objective] Head smut is an important disease that threats the yield of broomcorn millet seriously and the best way to control the disease is to plant resistant varieties. In order to screen the physiological and biochemical indexes of broomcorn millet for resistance to head smut, the activity of defensive enzymes and content of antioxidant were measured under the smut fungus stress. Furthermore, this will also provide theoretical supports for the breeding of broomcorn millet smut resistant varieties.[Method]Artificial inoculation of seed saturated inoculation was adopted to infect broomcorn millet and inoculated broomcorn millet plants were planted in field. A field experiment of resistance levels identification to screen the varieties with different resistance was conducted in 2012-2013. In 2014, the broomcorn millet varieties with different resistance levels were used to measure the activity of defensive enzymes and content of antioxidant at seedling stage (SS), elongation stage (ES), heading stage (HS) and filling stage (FS) under the smut fungus stress. The defensive enzymes include the phenylalanine ammonia lyase (PAL), ascorbate peroxide (APX), glutathione reductase (GR) and the antioxidant contained the ascorbate (AsA) and glutathione (GSH).[Result] After 2 consecutive years of resistance identification, the average incidence rate of Heigezao (R1), Lvtuochuan (R2) and Xiaomaimizi (R3) were 0, 0 and 0.73%, respectively, indicating that they were disease-resistant varieties; the average incidence rate of Huangyingshu (S1), Ning04-262 (S2) and Yym0965 (S3) was 19.71%, 19.86% and 32.28%, respectively, therefore, they belong to disease-susceptible varieties. With the stress of smut fungus, the PAL activity of susceptible varieties changed greater than that in resistant varieties, since the PAL activity of susceptible varieties was significantly higher at elongation stage (3 610.8 U·g-1 FW), but significantly lower at filling stage (2 425.0 U·g-1 FW) compared to that (2 520.7 and 2 946.0 U·g-1 FW, respectively) of resistant varieties. The APX activity showed the same trend in both kinds of varieties, which was decreased first and then increased; the minimum value appeared at the elongation stage. At heading stage and filling stage, the APX activity of susceptible varieties was 461.1 U·g-1 FW and 516.7 U·g-1 FW, which was significantly higher than that (361.5 U·g-1 FW and 428.2 U·g-1 FW) in resistant varieties. The GR activity was increased first and then decreased in all the varieties. At heading stage, the value of GR activity was significantly higher than that of other 3 stages. The difference between the 2 kinds of varieties was that the GR activity of susceptible varieties was obviously higher than that of resistant varieties at heading stage, the value of which was 271.9 U·g-1 FW and 167.4 U·g-1 FW, respectively. After inoculation with smut fungus, the content of AsA ranged from 147.7μg·g-1 FW to 344.8μg·g-1 FW without obvious regularity in all the varieties. Also there was no significant difference between resistant and susceptible varieties. The GSH content of resistant varieties was decreased significantly from seedling stage to heading stage, and then increased significantly at filling stage. The GSH content of susceptible varieties was also decreased significantly from seedling stage to heading stage, but there was no significant difference compared to filling stage. Therefore, the GSH content was obviously higher in resistant varieties (984.7μg·g-1 FW) than that in susceptible varieties (676.0μg·g-1 FW) at filling stage.[Conclusion] Different broomcorn millet varieties have different resistance levels to head smut disease. Smut fungus stress can cause the changes of defensive enzymes activity and antioxidant content in leaves of broomcorn millet. The PAL activity of broomcorn millet leaves at elongation stage and filling stage, APX activity at heading stage and filling stage, GR activity at heading stage, GSH content at filling stage are obviously different between resistant and susceptible varieties, which can be used as the physiological and biochemical indexes to identify head smut resistant germplasms in broomcorn millet.%【目的】黑穗病是威胁糜子产量的重要病害，防治黑穗病最有效的方法是种植抗病品种。本研究测定黑穗病菌胁迫对糜子叶片防御酶系活性及抗氧化物质含量的影响，筛选鉴定糜子黑穗病抗性的生理生化指标，为选育抗黑穗病的糜子品种提供理论支撑。【方法】以不同糜子资源为材料，田间种植条件下采用种子饱和接种法接种黑穗病菌，2012—2013年进行糜子黑穗病抗性鉴定，筛选不同抗性的糜子品种。2014年研究不同抗性糜子苗期（SS）、拔节期（ES）、抽穗期（HS）、灌浆期（FS）叶片防御酶系及抗氧化物质对黑穗病菌胁迫的响应，防御酶系测定苯丙氨酸解氨酶（PAL）、抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR）活性，抗氧化物质测定抗坏血酸（AsA）、还原型谷胱甘肽（GSH）含量。【结果】经连续两年糜子黑穗病抗性鉴定，黑虼蚤（R1）、驴驼川（R2）和小麦糜子（R3）平均发病率分别为0、0和0.73%，为抗病品种；黄硬黍（S1）、宁04-262（S2）和Ym0965（S3）平均发病率分别为19.71%、19.86%和32.28%，为感病品种。接种糜子黑穗病菌后，感病品种糜子叶片PAL活性变化幅度大于抗病品种，表现在拔节期PAL活性为3610.8 U·g-1 FW，显著高于抗病品种的2520.7 U·g-1 FW，而灌浆期为2425.0 U·g-1 FW，显著低于抗病品种的2946.0 U·g-1 FW。抗、感品种糜子叶片APX活性均呈先降低后升高的变化趋势，拔节期显著最低；感病品种糜子叶片APX活性在抽穗期和灌浆期（分别为461.1 U·g-1 FW和516.7 U·g-1FW）显著高于抗病品种（分别为361.5 U·g-1FW和428.2 U·g-1FW）。2类品种叶片GR活性变化呈先升高后降低趋势，抽穗期GR活性显著高于其他3个时期；且抽穗期感病品种叶片GR活性显著高于抗病品种，其中感病和抗病品种糜子叶片平均GR活性分别为271.9和167.4 U·g-1FW。糜子受黑穗病菌胁迫后，6个品种叶片AsA含量在147.7—344.8μg·g-1FW范围内波动，无明显规律，且抗、感品种间无显著差异。抗病品种糜子叶片GSH含量从苗期到抽穗期显著降低后到灌浆期又显著升高，而感病品种糜子叶片GSH含量从苗期到抽穗期显著降低后到灌浆期并无显著变化，并且灌浆期抗病品种叶片GSH含量为984.7μg·g-1FW，显著高于感病品种的676.0μg·g-1FW。【结论】不同糜子品种对黑穗病的抗性不同，黑穗病菌胁迫可引起糜子叶片防御酶活性及抗氧化物质含量变化，拔节期和灌浆期PAL活性、抽穗期和灌浆期APX活性、抽穗期GR活性、灌浆期GSH含量在抗病品种和感病品种间存在显著差异，可作为鉴定糜子对黑穗病抗性的生理生化指标。