Effects Of Light On Biological Characteristics And Enzyme Activities Of Two Ginseng Pathogens

Ginseng(Panax ginseng C.A.Mey.)is a perennial herb of Araliaceae,it has high medicinal value and is a valuable traditional Chinese medicine.In recent years,with the change of ginseng cultivation environment,ginseng gray mold and black spot are seriously harmful in ginseng producing areas in Northeast China,which has become one of the limiting factors affecting the healthy development of ginseng.In this paper,the effects of environmental factors on the growth and development of the two pathogens,the activities of extracellular degradation enzymes and the defense system of ginseng leaves infected by the pathogens were studied,in order to provide theoretical reference for the study of the two ginseng diseases and provide new ideas for disease control.The main findings are as follows:1.The biological characteristics of Botrytis cinerea and Alternaria panax of ginseng were studied.(1)The mycelial growth of B.cinerea was the fastest under the condition of temperature20℃,p H 5 and total darkness;When the temperature was 20℃,the p H was 6,and the light and dark alternated for 12 hours,the spore production of pathogenic bacteria was the largest;The optimum conditions for conidia germination were as follows: temperature 20℃,relative humidity 100%,alternating light and dark for 12 h,p H 5 and 6,under which the spore germination rate was the highest;The most efficient carbon source and nitrogen source were glucose and peptone respectively;The temperature of mycelium death was 50℃,and the temperature of conidia death was 55℃.(2)The mycelial growth of A.panax was the fastest at25℃ and p H was 6.The optimum carbon source was sucrose and the optimum nitrogen source was peptone;When the temperature was 30℃ and p H was 6,sporulation reached the maximum;The germination rate of conidia was the highest at 20℃,relative humidity 100% and p H 7;Total darkness was conducive to mycelial growth,spore production and spore germination.Different light quality had a great effect on the mycelial growth of B.cinerea and A.panax,and blue light had a significant inhibitory effect on the mycelial growth.2.The production conditions of extracellular degrading enzymes from B.cinerea and A.panax of ginseng were systematically studied.The results showed that both pathogens could produce cutinase and cell wall degrading enzymes.The optimum culture days for producing cutinase by B.cinerea and A.panax were 8 days and the optimum p H was 6.The activity of cutinase B.cinerea was the highest at 20℃,while that of A.panax was 25℃;The pectinase activity of B.cinerea and A.panax reached the peak at 12 days,while the cellulase activity of B.cinerea was the highest at 10 days,and that of A.panax was the highest at 6 days.The optimum p H of cell wall degrading enzymes produced by B.cinerea was 6,while that of A.panax was 7.Blue light could significantly inhibit the activity of extracellular degrading enzymes produced by two ginseng pathogens.3.Studies on the changes of antioxidant enzymes in ginseng leaves infected by two pathogens and the occurrence of diseases with different light quality showed that light quality could regulate the activity of antioxidant enzymes in ginseng leaves and the activity of antioxidant enzymes in blue and red light treatments was higher than that in control group and yellow light group before infection.After the pathogen infection,the leaf disease spot expanded less under blue and red light,the disease degree was light,and the antioxidant enzyme increased late and the change range was small.It was proved that blue light and red light could better regulate the defense system of ginseng leaves,improve the disease resistance and reduce the occurrence of diseases.