施硅提高小麦防御孢囊线虫病的组成型和诱导型抗性机制

Silicon application improves constitutive and inducible resistance of wheat against cyst nematode disease

【目的】孢囊线虫病在我国广泛存在,危害粮食安全与环境健康,严重影响了农业的可持续发展。硅作为一种诱导因子,在植物抗病性方面具有重要的作用,研究施用硅肥诱导小麦防御孢囊线虫病的作用机制对环境保护和小麦生长具有十分重要的意义。【方法】以菲利普孢囊线虫(Heterodera filipjevi)为供试孢囊线虫,首先开展硅肥施用水平盆栽试验,在不接虫和接虫条件下,分别设置5个硅肥施用水平:0、0.25、0.5、1、2 g/kg。在小麦接虫后2个月,取样测定小麦单株孢囊量、植株生长指标,筛选出最优硅肥施用浓度。以最优施硅水平继续进行施硅与接虫2×2双因素盆栽试验,共4个处理:不施硅不接虫(CK)、施硅不接虫(Si)、不施硅接虫(Cyst)、施硅接虫(Si×Cyst)。接虫2个月后,取样分析小麦硅、营养物质(可溶性糖、可溶性蛋白和游离氨基酸)、次生代谢物质(木质素和总酚)以及活性氧(过氧化氢)含量,将未接虫处理小麦的相关成分含量定义为组成型抗性,接虫前后的各成分差值定义为诱导型抗性,探究施硅提高小麦防御孢囊线虫能力的组成型和诱导型抗性机制。【结果】浓度为0.5 g/kg的硅肥处理使小麦单株孢囊量显著减少了67.74%,且显著提高了小麦地上部鲜重、株高、叶绿素相对含量(SPAD)、地下部鲜重、根总长、根表面积、根尖数和根系活力。与不施硅处理(Si 0 g/kg)相比,施硅处理(Si 0.5 g/kg)的组成型地上和地下部硅含量分别显著提高76.50%和116.60%,诱导型地下部硅含量显著下降;施硅显著提高了营养物质中组成型可溶性糖和可溶性蛋白含量,组成型游离氨基酸含量显著降低了33.10%,增加了诱导型可溶性糖和游离氨基酸含量;施硅后的组成型木质素、总酚含量分别显著增加37.98%和35.55%,诱导型含量均显著减少;诱导型过氧化氢含量在施硅后显著降低了25.39%。PCA与相关性分析结果表明,地上部鲜重及株高、组成型游离氨基酸含量、诱导型地上部硅含量及过氧化氢含量与小麦防御孢囊线虫病能力的关系最为紧密。【结论】施用硅肥通过对小麦硅含量、营养物质、次生代谢物质以及活性氧的影响,从小麦的组成型抗性和诱导型抗性方面提高了小麦对孢囊线虫病的抗性。

【Objectives】Cyst nematode disease widely happens in China,threatening the food security and environmental health,as well as the sustainable development of agriculture.Silicon,as an inducer,plays a pivotal role in enhancing plant disease resistance.Studying the mechanism underlying wheat defense against cyst nematode diseases induced by silicon fertilizer holds immense significance for both environmental protection and wheat production.【Methods】Employing Heterodera filipjevi as the test nematode,a pot experiment was carried out.Five levels of silicon fertilizer were established under the circumstances of no feeding and inoculation:0,0.25,0.5,1,and 2 g/kg,respectively.Two months after inoculation,the amount of sporocyst and plant growth index of wheat were measured,and the optimal silicon fertilizer application concentration was selected.The 2×2 two-factor pot experiment of silicon application and insect-feeding was carried out at the optimal silicon application level,making four treatments in total:neither Si application nor nematode infection(CK),Si application without nematode infection(Si),no Si application but with nematode infection(Cyst),and both Si application with nematode infection(Si×Cyst).After 2 months of inoculation,the contents of silicon,nutrients(soluble sugars,soluble proteins and free amino acids),secondary metabolites(lignin and total phenols)and reactive oxygen species(H2O2)in wheat were analyzed.The content or activity of the tested indices in wheat without cyst nematode infestation was defined as the constitutive resistance.The difference between the indices before and after cyst nematode infestation was defined as inducible resistance.To explore the constitutive and inducible resistance mechanisms of silicon application to improve wheat defense against sporocystitis nematodes.【Results】Application of silicon fertilizer at 0.5 g/kg significantly decreased the number of cysts per plant by 67.74%,enhanced above-ground fresh weight,plant height,SPAD value,underground fresh weight,total root length,root surface area,number of root tips and root activity in wheat,so was used as the Si application rate in the followed experiment.Compared with no Si application,Si application(Si 0.5 g/kg)significantly increased the above ground and underground fresh weight of the constitutive type by 76.50%and 116.60%,while decreased the underground Si content in the induced type;enhanced the soluble sugar and soluble protein contents,but decreased the free amino acid content by 33.10%in constitutive type,and elevated inducible soluble sugar and free amino acid levels.Lignin and total phenol contents increased by 37.98%and 35.55%,respectively,while the inducer’s content decreased significantly.Furthermore,after silicon application,there was a reduction of 25.39%in induced hydrogen peroxide content.The results of PCA and correlation analysis showed that above-ground fresh weight and plant height,content of constituent free amino acids,content of silicon and hydrogen peroxide in induced above-ground were the best indexes.【Conclusions】Silicon fertilizer application can improve the resistance of wheat to cystitis nematodes through the effects of silicon content,nutrients,secondary metabolites and reactive oxygen species in wheat,from the aspects of constitutive resistance and induced resistance.