尖孢镰刀菌侵染下香蕉幼苗抗病生理响应研究

香蕉枯萎病由土传病菌尖孢镰刀菌侵染引起,为探究病原菌侵染过程中香蕉植株的抗病生理响应,本研究利用温室培养植株接种病原菌的方法,测定病原菌侵染之后叶绿素含量、抗病防御酶活性、总酚含量、木质素含量、可溶性糖含量和氨基酸含量。结果表明:(1)随着病原菌的侵染,叶绿素含量显著降低。在侵染第16天时,发病植株叶绿素含量相对于健康植株降低44%;(2)病原菌侵染之后,植株各部位抗病防御酶苯基丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活性显著提高;(3)随着病情的加剧,酚类物质和木质素逐渐在植株体内累积;(4)病原菌侵染之后,香蕉植株叶片和假茎可溶性糖含量显著增加,但根系可溶性糖含量显著降低。当植株发病等级为I级时,叶片和假茎可溶性糖含量增加至未侵染植株的1.53和1.62倍,根系可溶性糖含量降低至未侵染植株的67%;(5)当植株发病等级为II级时,叶片和假茎氨基酸含量分别增加至未侵染植株的的3.01、5.38和1.99倍。综上所述,病原菌侵染之后,香蕉植株会通过提高抗病防御酶活性,合成抗病物质酚类和木质素,同时,也会主动累积可溶性糖和氨基酸,来缓解由于病原菌侵染之后所造成的渗透胁迫。

Physiological Resistance Response of Banana Seedlings to Fusarium oxysporum

Banana wilt disease was caused by soil-borne pathogen Fusarium oxysporum. Hydroponic experiments with pathogen inoculation were conducted in the greenhouse to observe the resistance response of banana seedlings to F. oxysporum. The banana seedlings infected with F. oxysporum were determined in terms of chlorophyll, total phenolic, lignin, soluble carbohydrate and amino acid and defense enzyme activity. When infected with the pathogen, the banana seedlings reduced their chlorophyll content significantly, and at the day 16 their chlorophyll content was decreased by 44% compared with the healthy plants.After infected with the pathogen, the banana seedlings increased significantly the activities of the defense enzymes like phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO). When seriously infected with the pathogen, they increased gradually their contents of total phenolic acid and lignin. After infected with the pathogen, the banana seedlings increased significantly their soluble carbohydrate content in the leaves and pseudostem, but decreased their soluble carbohydrate content in roots. When the disease grade was ranked I, the infected banana seedlings increased the content of soluble carbohydrate in the leaves and pseudostem by 1.53 times and 1.62 times as against the non-infected plants, and reduced their content of soluble carbonhydrate in the root by 67%. At the disease grade II, the infected banana seedlings increased their amino acid content by 3.01 times, 5.38 times and 1.99 times in the leaves, pseudostem and root as against the noninfected plants, respectively. It is concluded that when infected with the pathogen banana plants synthesized the phenols and lignin to increase the activity of disease defense enzyme and at the same time, accumulated actively the soluble carbohydrates and amino acids to ease the osmotic stress caused by the pathogenic infection.