| In this paper,forty-one tobacco varieties(system)were used as test materials to carry out the artificial inoculation experiment of potato virus Y(PVY),to investigate their incidence and identify the degree of PVY resistance.Based on the disease index(D)and the resistance index(RI),the taxa and subgroups were divided by Euclidean distance-Ward's cluster analysis.Physiological and biochemical indexes such as agronomic traits and antioxidant enzyme activities were determined 36 days after inoculation in twelve tobacco varieties with different resistances.Comprehensive evaluation and anti-inductive ranking were performed using the membership function method.Four representative varieties of high resistance(SY04-3),middle resistance(Yanshai No.6),middle sense(Yunyan 87)and susceptible(NC95)were selected as the test materials,and the changes of physiological indexes such as net photosynthetic rate and protective enzyme activity before and after inoculation were studied.The main findings are as follows:1)Seven materials including SY04-3,Longjiang 981 and CV91 are PVY high resistant varieties;Seventeen materials such as Yanshai No.6,CF209,and Yanji Melaleuca Tower are PVY middle resistant varieties;Fourteen materials such as ZhongYan 90,large yards thin,Yunyan 87 are PVY middle sense varieties;Three kinds of materials such as Zhongyan 100,NC89 and NC95 are PVY susceptible varieties.2)Based on the disease index(D)and the resistance index(RI),the Euclidean distances among different cultivars were analyzed.The greater the difference in resistance between different resistant cultivars,the greater the gap between Euclidean distances.Through clustering analysis,they were divided into two major groups:disease resistance and susceptible,and four subgroups:high resistance,middle resistance,middle sense,and susceptible.There are highly significant differences between the two major groups,but there are significant differences among the four subgroups.The species and lines included in the taxa and subgroups classified by Euclidean distance-Ward's clustering analysis were the same,and the disease resistance classification results were also consistent.3)36 days after PVY inoculation,twelve different resistant tobacco varietieswere selected for inoculation and control treatments to determine agronomic traits,dry matter accumulation,antioxidant enzyme activities and other physiological indicators.In the plant height,leaf area,dry matter accumulation,SOD and CAT activity,photosynthetic rate,chlorophyll,the inoculation treatment was lower than the control treatment,showing a decreasing trend.In POD activity,MDA content and electrical conductivity,the inoculation treatment was higher than the control treatment,showing a trend of increase.The comprehensive ordering of the membership functions of 12 tobacco varieties against PVY is strong and weak:SY04-3>Longjiang 981>Yanshai No.6>Jiyan N0.9>Laohe-1>CF222>Yanshai No.7>SZ08-4>Yunyan 87>Large yards thin>Jiyan NO.10>NC95.The SY04-3 had the highest membership function value among the twelve tobacco varieties with 0.9165,the strongest resistance,the NC95 has the lowest membership function value,0,and the weakest resistance.4)In terms of plant height,leaf area,and dry matter accumulation,the values of inoculation or non-inoculation treatment showed an upward trend with the increase of inoculation time.35 days after inoculation,the inoculation treatment was lower than the control,and the decreasing range was SY04-3,Yanshai No.6,Yunyan 87,and NC95 in ascending order.In the three aspects of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities,it was characterized that with the increase of inoculation time,the enzyme activities of all varieties that had undergone the control treatment showed an upward trend,and all varieties that had taken the inoculation treatment showed a trend of increasing first and then decreasing;7-21 days after inoculation,those of the four varieties with the inoculation treatment were basically higher than with the control treatment,the largest increase was SY04-3,the smallest was NC95;but 35 days after inoculation,those of the varieties with the inoculation treatment were basically lower than with the control treatment,and the descending order from small to large was SY04-3,Yanshai No.6,Yunyan 87,and NC95.With the increase of inoculation time,the photosynthetic rate of all varieties which had been treated with the control treatment increased gradually,and all varieties reduced gradually with the inoculation treatment.7-35 days after inoculation,the photosynthetic rate of the four varieties treated with the inoculation treatment was lower than that of the control treatment of the same variety.After inoculation,the photosynthetic rate of the four varieties had a decrease,and the decrease of photosynthetic rate of SY04-3 was the smallest,and the decrease of NC95 was the largest.The change law of chlorophyll content is almost the same as that of photosynthetic rate.With the advance of the inoculation time,the relative conductivities of the four varieties treated with the control treatment showed no obvious regularity and the amplitude of fluctuation was small,but that of the four varieties treated with the inoculation treatment increased gradually and there were significant differences(P<0.05).14 days after inoculation,the relative conductivities of the four varieties treated with the inoculation treatment was higher than that of the control treatment of the same variety.35 days after inoculation,compared to the control treatment,relative conductivity of SY04-3 had the lowest increase,and NC95 had the highest increase.Thus,it can be seen that on the physiological and biochemical indicators at 0-35 days after inoculation,the best-performing variety is the high resistance variety(SY04-3),followed by the middle resistance variety(Yanshai No.6),and again the middle sense variety(Yunyan 87),the last is the susceptible variety(NC95). |
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