Effects Of Garlic Allelochemical Diallyl Disulfide On Cucumber Growth And Alleviating Cinnamic Acid/fusarium Wilt Stress

Cucumber is an important vegetable crop.The problems of self poisning and soil borne diseases are very prominent in our country facility production.Garlic is a very important horticultural crop which has stronger allelopathic potential.Intercropping or rotation with garlic can not only reduce diseases and insect pests of receptor plant,but also promote the growth of receptor plants.Diallyl disulfide（DADS）is the main allelochemical of garlic.Studies have shown that DADS can induce double dose dependent effect on tomato root growth,which is at lower concentration improves growth,while at higher concentration causes inhibition.However,it is not clear that the allelopathy mechanism of DADS on cucumber plants,and the alleviation effect of cinnamic acid toxicity and fusarium wilt on cucumber growth.After DADS treatment,cucumber root germination and seedling growth were observed.Moreover,root activity,hormone levels,apical meristem size and mitosis related genes expression were also analyzed.The alleviation effect of cinnamic acid toxicity and fusarium wilt on cucumber growth was explored.The main results are as follows:1.DADS can induce double dose dependent effect on cucumber root growth,which is at lower concentration（no more than 600μl/l）behave promotion effect,while at higher concentration（higher than 1000μl/l）have an inhibitory effect.Our results reveal that the low concentrations of DADS can improves cucumber root architecture and promote main root elongation.The promotion effect at low concentrations of DADS is by regulating hormone balance（IAA,GA₃,ABA and CTK）and inducing of mitosis related genes（CDKA and CDKB）expression.2.DADS itself has strong biological activity.It can inhibit the spore and mycelium growth of fusarium oxysporum and its inhibitory effects are more significant with the increase of DADS concentration.Thus,DADS at higher concentrations completely inhibits the fusarium growth by causing abnormality in mycelium morphology and spores.Furthermore,DADS decrease peroxidase（POD）,catalase（CAT）activities,malondialdehyd（MDA）content,while,increases superoxide dismutase（SOD）activity as compared to fusarium treatment.Suggesting that the DADS maybe scanvenging reactive oxygen species（ROS）,which leads to reduced membrane damage,improved resistance of cucumber,and hence,promotes the growth of cucumber.3.In the condition of hydroponics,the self-toxin cinnamic acid is toxic to cucumber seedling growth,but not in matrix culture.Low concentration of DADS at 200μl/l not only can promote cucumber seedling growth to some extent,but also can ease the low concentrations of self-toxin cinnamic acid stress at a certain level.While at higher concentrations of cinnamic acid,DADS might not have any significant effect.