Study On The Biological Characteristics Of FOC-RA-5 And Content Variations Of Several Physiological And Biochemical Substances In Cucumber Leaves Inoculated With It

The morphological characteristic,toxin-producing capability and content of metabolite of the attenuated strains for Fusarium oxysporum f. sp. Cucumerinum (FOC-RA-5) were researched in this study. The attenuated strains for Fusarium oxysporum f.sp.Cucumerinum (FOC-RA-5) was inoculated into the cucumber which called "Jinchun No.4", then the content of physiological and biochemical substances,which included tannins, ferulic acid,chlorogenicacid,free amino acid, reducing sugar,total sugar,nitrite,nitrate and H+ of leaves at the same position were determined respectively 1 day, 3days,5days,7days,7days,9days,11days,13days,15days later,and the correlation analyses with disease index were done.The results were as follows:(1)The average growth rate of FOC-RA-5 and FOC were 7.49mm and 8.02mm per day, and the average growth rate of FOC-RA-5 decreased by 6.66%. There was no significant difference between FOC-RA-5 and FOC about colony morphology in PDA medium. The front side of the colonies were both white like batts,and the back side were brown-black,but the hyphae density and diameter of FOC-RA-5 were both tinner than FOC.The hyphae expansion capability of FOC-RA-5 a little weaken than FOC, the number of bifurcate hyphae and the number of generator cell were less than FOC’s, and the number of spore was extremely less than FOC’s, either.The spores morphologies of FOC-RA-5 and FOC were oblong and colorless transparence,but the spores of FOC-RA-5 ware a little smaller than FOC’s. The germination rate of spores of FOC-RA-5 was extremely less than FOC.(2)The toxin-producing capability of FOC-RA-5 decreased significantly than FOC. The content of fusaric acid in FOC-RA-5 were extremely less than FOC’s,and there was no significant difference between FOC-RA-5 and FOC in the content of soluble protein. The content of malondialdehyde in FOC-RA-5 extremely increased by 18.78% than FOC,and the contents of cellulose,β -D-Glucosidase and pectinase extremely decreased by 69.32%、52.58%、 50.33% than FOC.(3) The content variation of tannin within a gentle decline before the increasing, then decreased,and peak appeared in 11 days after inoculation,and was significantly higher than control’s 7days,9days,11days,13days,15days later.The contents variations of ferulic acid and chlorogenic acid both increased at first and then decreased,and respectively in 7 days,9 days after inoculation appeared peak.The content of ferulic acid was significantly higher than control’s 3days,5days,7days,9days,11days later,and the content of chlorogenic acid was significantly higher than control’s lday,3days,5 days,7days,9days,11days later.Free amino acids presented the trend that fluctuate within a certain scope,and two peaks appeared 5 days and 13 days later. The content of free amino acids was significantly higher than control’s all the time. The content of reducing sugar showed a trend that rise at first and then fall, the peak appeared at 7day after processing.And the contents of reducing sugar were significantly lower than control all the time. The content of total sugar showed a trend that rising after decline first, the minimum and maximum respectively appeared at 3 days,7 days later. The content’s of total sugar was lower than the control within 5 days,and higher than the control’s 7 days later. There was no significant difference between FOC-RA-5 and FOC in the content of nitrite.The content of nitrite in FOC-RA-5 were between 0.04 and 0.06ug/g,and the content of nitrite in FOC were between 0.03 and 0.06μg/g.The content of nitrate fall first,and then fluctuate within a certain range. The content of nitrate in FOC-RA-5 was significantly lower than control’s 3 days,5 days,7 days,15 days later.The content of hydrogen ion concentrations present the trend that rise firstly and then fall,and the peak appeared at 9 days after processing.and was significantly higher than control’s 3 days later.(4)The correlation analyses between substances contents and disease index showed that the tannin, ferulic acid, chlorogenic acid contents, total sugar and plant disease resistance were significant positive correlation, nitrate,reducing sugar and plant disease resistance were significant negative correlation, but there was no significant correlation between free amino acid content, nitrite and plant disease resistance.