Allelopathy Of Root Exudates Of Different Resistant Muskmelon Cultivars On Fusarium Wilt

Fusarium wilt of muskmelon is one of the most serious plant diseases in China,its control process is very difficult.Due to continuous cultivation for many years,the content of root exudates in soil increased.In this paper,the root exudates of susceptible cultivars（Jingtian 6and Riben Tianbao）and susceptible cultivars（Xinmi 1 and Ludi Guawang）are measured and their phenolic acid contents are determined.The allelopathic effects of the root exudates of the muskmelon resistant cultivar and susceptible cultivar on the mycelia growth,seed germination and seedling growth of Fusarium oxysporum were clarified,which provided a theoretical basis for relieving the occurrence of the Fusarium wilt.1.Resistance identification of of 20 muskmelon cultivars on Fusarium wilt.Isolation and purification of muskmelon Fusarium wilt in parts of Liaoning,Fusarium oxysporum obtained and strong pathogenic strains used to identify resistance of 20 muskmelon cultivars.The results showed that there are 2 resistant cultivars（R）,namely Jingtian 6 and Riben Tianbao,and 10 susceptible cultivars（S）,the incidence of Xinmi 1 and Ludi Guawang are higher,and there are 7 middle resistance cultivars（MR）,1 high sensitive cultivars（HS）,no high resistant cultivar（HR）.2.Allelopathic effects of root exudates from resistant and susceptible muskmelon cultivars.Research on the allelopathy of the root exudates of the tested muskmelon cultivars Jingtian6,Riben Tianbao,Xinmi 1 and Ludi Guawang.The results showed that the root exudates of different resistant cultivars of muskmelon have different degrees of allelopathic effects on seedling growth,seed germination and mycelial growth of Fusarium oxysporum.The root exudates of muskmelon cultivars on the germination of muskmelon seeds under treatment conditions showed allelopathic effects.However,the growth trend of muskmelon seedlings are negatively related to the treatment concentration.The plants of the muskmelon seedlings treated with root exudates of Xinmi 1 and Ludi Guawang muskmelon are the shortest and the fresh weight of roots are least.The seedlings treated with the root secretions of Jingtian 6 and Riben Tianbao are slightly lower than those of seedlings treated with sterile water.The difference in fresh weight is not significant.Jingjing 6 and Riben Tianbao root stem secretions inhibit the growth of Fusarium oxysporum mycelia.As the concentration increases,the growth of F.oxysporum mycelia promoted by Xinmi 1 and Ludi Guawang.The results showed that the tested muskmelon cultivars Jingtian 6 and Riben Tianbao treasure root exudates reduced the incidence of muskmelon Fusarium wilt.The susceptible cultivars Xinmi 1 and Ludi Guawang root exudates increased the incidence of Fusarium wilt.Pot experiment confirmed that the root exudates of tested muskmelon resistant cultivars（Jingtian 6 and Riben Tianbao）have inhibitory effects on the occurrence of muskmelon Fusarium wilt.The incidence of Fusarium wilt significantly decreased,and the root exudates of tested muskmelon susceptible cultivars（Xinmi 1 and Ludi Guawang）could aggravated the incidence of muskmelon Fusarium wilt.3.Comparative research on allelochemicals of root exudates from resistance and sensitive muskmelon cultivars.Separation and identification by HPLC method showed that the benzoyl benzoate,diethyl phthalate,dibutyl phthalate and p-tolyl benzoate benzene are both contained in the root exudates of the resistant cultivar（Jingtian 6）and the resistant cultivar（Riben Tianbao）;The root exudates of the susceptible cultivar（Xinmi 1）and susceptible cultivar（Ludi Guawang）contained cinnamic acid,phthalic acid,syringic acid,and benzoic acid.Different concentrations of benzyl benzoate,diethyl phthalate,p-tolyl benzoate and dibutyl phthalate all showed low concentrations of seed germination and promote high-level inhibition allelopathy.The cinnamic acid and benzoic acid all showed inhibitory effects on seed germination and increased with increasing treatment concentration.Benzoic acid benzoate has the most significant inhibitory effect at a concentration of 0.50mmol·L^-1,When the plate is cultivated for 3 days,cinnamic acid and benzoic acid are treated at a concentration of 0.05-0.50mmol·L^-1,after 5-7d cultivated,showed low concentration promotion and high concentration inhibition.Dibutyl phthalate and p-tolyl benzoatel exhibited inhibitory effects at concentrations of 0.05-0.50mmol·L^-1.4.Effects of muskmelon root exudates on the expression of related regulatory genes in Fusarium oxysporum.Real-time PCR technique is used to research the expression of Fusarium oxysporum related genes in the root exudates of Jingtian 6,Xinmi 1,p-tolyl benzoate and cinnamic acid.Test results showed that in four different treatments,the expression levels of Fochs V gene,FUBT gene,SOD gene,and POD gene in the root exudates of resistant cultivar（Jingtian 6）showed a decreasing trend after treatment,which is significantly different from that of CK;After treatment in the root exudates of the susceptible cultivar（Xinmi 1）,the expression level showed an upward trend,which further indicated that it increased the incidence of disease caused by Fusarium oxysporum.After treatment with two kinds of phenolic acids,the inhibition of p-tolyl benzoate is the most significant,and the difference in expression is obvious.The expression level of Fochs V gene is significantly increased after cinnamic acid treatment.It can be seen that the phenolic acids in resistant cultivars can inhibit the growth of Fusarium oxysporum and reduce the incidence of disease caused by Fusarium wilt.The phenolic acids in susceptible cultivars promoted the growth of Fusarium oxysporum and aggravated the occurrence of Fusarium wilt.