山苍子精油对辣椒疫霉生长发育的影响及对辣椒疫病的防效
Effects of Litsea cubeba essential oils on the growth and development of oomycete pathogen Phytophthora capsici and pepper blight

为明确山苍子精油防治植物疫病的应用前景，在室内离体条件下测定其对辣椒疫霉Phytophthora capsici菌丝生长、孢子囊形成与萌发、游动孢子萌发的毒力，观测经山苍子精油处理后菌丝生长量及形态结构、细胞膜通透性和可溶性蛋白含量的变化；采用离体叶片法和灌根法分别测定山苍子精油对辣椒疫病的预防效果和治疗效果。结果表明，山苍子精油对辣椒疫霉的菌丝生长、孢子囊形成与萌发以及游动孢子萌发的有效中浓度EC50分别为161.49、29.68、231.80、90.68 mg/L；EC50和EC75的山苍子精油处理显著降低了辣椒疫霉菌丝的鲜重和干重，抑制率均在49.71%以上，亦可显著降低菌丝中可溶性蛋白含量，抑制率分别为10.77%和18.47%；用山苍子精油处理菌丝后，其顶端生长受到抑制，分枝明显增多、间距缩短；细胞膜通透性增大。1 000 mg/L山苍子精油对辣椒疫病的预防效果达63.33%（离体叶片法），2 000 mg/L精油对辣椒疫病的预防效果和治疗效果分别达80.00%和68.00%（灌根法，7 d），均显著高于对照药剂嘧菌酯。表明山苍子精油是辣椒疫霉的有效抑制剂，在辣椒疫病综合治理中具有较大的应用潜力。
To clarify the application prospect of Litsea cubeba essential oils for controlling Phytophthora diseases, the effects of L. cubeba essential oils on the growth and development of Phytophthora capsici were investigated under laboratory conditions. The results showed that the EC50 values for mycelial growth, sporangiurn formation, sporangium germination and zoospore germination of P. capsici were 161.49, 29.68, 231.80 and 90.68 mg/L, respectively, after treatment with L. cubeba essential oils. The essential oil treatment (EC50 and EC75) led to significant decrease of the fresh weight and dry weight of the mycelia, with an inhibition rate of more than 49.71%. Moreover, the treatments at EC50 and EC75 concentrations could significantly reduce the soluble protein content in the mycelia, with the inhibition rates of 10.77% and 18.47%, respectively. Morphological and structural studies showed that the essential oil treatment led to significant inhibition of hyphal top growth, increase of branches, shortening of mycelium space and even increase of cell membrane permeability. The preventive effect of L. cubeba oil treatment at 1 000 mg/L against pepper blight reached 63.33% (in vitro leaf). The preventive and therapeutic effects against pepper blight were 80.00% and 68.00%, respectively, at the concentration of 2 000 mg/L seven days after drenching roots, significantly higher than that of the control (azoxystrobin). These results demonstrated that L. cubeba essential oil was an efficient inhibitor of P. capsici, and might play an important role in the integrated management of pepper blight.