| Muskmelon（Cucumismelo L.）is an important melon crop in protected cultivation.Fusarium wilt of muskmeloncaused by long-term continuous croppingis the main restriction in worldwidemuskmelonproduction.As important substances for plants to produce autotoxicity,phenols in melon plants and root exudates are accumulated by continuous cropping,which is related to Fusarium wilt of muskmelon.Many studies showed that the occurrence of Fusarium wilt was effected by the content of coumarin,salicylic acid,ferulic acid,cinnamic acid and other phenolics,and the effects of exogenous phenolic substances on the occurrence of Fusarium wilt of muskmelon are unclear.The purposes of this research are toevaluate the influences of coumarin and cinnamic acidwhichwererespectivelythe most inhibitory and promoting growth of Fusariumoxysporum f.sp.melonis（FOM）on the reproduction and pathogenicityof FOM,plant and root growthof muskmelon,and the resistance of Fusarium wilt of muskmelon to provide technical support for the green prevention and control of Fusarium wilt of muskmelon.The main results are as follows:1.The growth of FOM was inhibited by coumarin and salicylic acid,and promoted by cinnamic acid and ferulic acid at 0.25-4.0 mg·L-1.The inhibitory effects on colony diameter and mycelial dry weight of coumarin were stronger than salicylic acid,while the promote action of cinnamic acid were higher than ferulic acid.It was observed that coumarin inhibited the spore germination of FOM andcinnamic acid promoted the spore germination of FOM at0.25-4.0 mg·L-1.The maximum inhibition in spore production and germination of FOM was found in treatment with coumarin at the concentration of 1mg·L-1,which significantly promoted seed germination of muskmelon,while the maximum promotion in spore production and germinationof FOMwas found in treatment with cinnamic at the concentration of 1mg·L-1,which significantly inhibited seed germination of muskmelon.2.The effects of coumarin and cinnamic acid at 1 mg·L-1on the growth and disease resistance of muskmelon plants weredetermined.Pot experiments results indicated thatcoumarin enhancedplant growth and dry matter accumulation,increased root absorption activity and reduced root cell damage,while cinnamic acid significantly inhibited melon plant growth and dry matter accumulation,reduced root absorption activity and aggravated root cell damage.3.Experiments were conducted to test the influence of coumarin and cinnamic acid on roots of muskmelon plants.The results showed thatcoumarin significantly enhanced the activity of chitinase andβ-1,3-glucanase activity in muskmelon roots and increased the content of disease resistant substances such as total phenols,flavonoids and lignin,and significantly reduced the incidence of Fusarium wilt of muskmelon,,while cinnamic acid obviously decreased chitinase andβ-1,3-glucanase activity in muskmelon roots and the content of disease resistant substances such as total phenols,flavonoids and lignin,and significantly aggravated the occurrence of Fusarium wilt of muskmelon,.The above determinations indicate thatcoumarin significantly inhibited the growth,reproduction and pathogenicity of FOM,promoted the growth of melon plants,improved their defense enzyme activity and increased the content of disease resistant substances,reduced the incidence of Fusarium wilt of muskmelon,while cinnamic acid significantly promoted the growth,reproduction and pathogenicity of FOM,inhibited the growth of melon plants,reduceddefense enzyme activity and the content of disease resistant substances,which caused root cell damage,and improved the incidence of Fusarium wilt of muskmelon.Based on the above results,the conclusions can be drawn thatcoumarin inhibited the occurrence of Fusarium wilt of muskmelon by inhibiting the pathogenic factors of FOM and enhanced the disease resistance factors of muskmelon and cinnamic acid promoted the occurrence of Fusarium wilt of muskmelon by enhancing the pathogenic factors of FOM and weakening the disease resistance factors of melon,which can be used to breed the muskmelon varietieswith highercoumarin or lowercinnamic acid for the prevention of Fusarium wilt of muskmelon. |
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