| Seeds are the first and crucial step in agricultural production.Once the seed is infected,the plant is at risk of disease in the first step of production.Seeds are also known as the primary source of plant diseases and the main way of disease transmission.Seed-borne diseases seriously threaten the yield and quality of cucumber,leading to yield reduction or even loss of harvest,and causing huge economic losses to farmers.In production,chemical pesticides are usually used to prevent and control seed-borne diseases.Although the control effect is good,long-term use of chemical pesticides not only causes drug resistance in plants,but also seriously pollutes the agricultural ecological environment.Pesticide residues in food directly harm people’s health.On the basis of the pre-test,cucumber seeds were dry-heat treated for 2h,4h,6h,8h,10 h and 12 h at 60℃,70℃,80℃,90℃ and 100℃ respectively.The control(CK)was the same batch of cucumber seeds without dry-heat treatment.The effects of dry heat treatment on cucumber seed pathogen activity,growth and development were studied by measuring germination index,cucumber seed pathogen activity,cucumber growth and development index after field planting,and the occurrence of powdery mildew,downy mildew and keratosis.The optimal temperature and time to inactivate cucumber seeds through dry heat treatment without significantly reducing seed germination were selected to provide reference for green cucumber production.The specific results are as follows:1.Effect of dry heat treatment on cucumber seed germination: the germination potential of dry heat treatment at 60℃,70℃ and 80℃ was significantly higher than that at 90℃ and 100℃,and the germination potential of dry heat treatment at 90℃ and 100℃was significantly lower than that of control;At 60℃ for 4h,6h,8h,10 h,70℃ for 2h,4h,6h,8h,10 h,80℃ for 4h,6h,the germination potential was higher than that of the control,with no significant difference,and the germination potential was 72.67%-78.00%,among which the highest germination potential was 70℃ for 4h,the germination potential was78.00%.The germination rate of 60℃,70℃ and 80℃ was significantly higher than that of90℃ and 100℃,and that of 90℃ and 100℃ was significantly lower than that of the control.The germination rate of 60℃ for 6h,8h,10 h,12h,70℃ for 2h,4h,6h,8h,10 h,80℃ for 4h,6h was higher than that of the control,with no significant difference,and the germination rate was 90.00%-98.00%,among which the highest germination rate was70℃ for 4h,the germination rate was 98.00%.2.Effect of dry heat treatment on pathogen activity of cucumber seed: in PDA medium(for fungal pathogen detection),there was no significant difference in pathogen activity between different treatments and control when the dry heat treatment temperature was 60℃;When the dry heat treatment temperature was 70℃ and 80℃,the activity of fungal pathogens in each treatment was significantly lower than that in the control and other treatments.The inactivation rates of 70℃ for 2h,4h,6h,8h,10 h and 80℃ for 4h,6h were 88.00%-91.33%.The highest inactivation rate was 91.33% for 4h at 70℃.In LB medium(for bacterial pathogens detection),the inactivation rate of each treatment at 60 ℃ was 0,no significant difference from the control.Under dry heat treatment at 70℃ and 80℃,the activity of bacterial species transmission was significantly lower than that of control and other treatments.The inactivation rates of 70℃ for 2h,4h,6h,8h,10 h and 80℃ for 4h,6h were 90.00%-96.67%.The treatment with the highest inactivation rate was 4h at 70℃,and the inactivation rate was 96.67%.3.Growth indicators: The plant height,stem diameter,number of leaves,maximum leaf area,number of female flowers within 10 nodes,number of female flowers within 10 to 20 nodes and yield of each treatment were higher than those of the control.The plant height,stem diameter and maximum leaf area of the treatment at 70 ℃ for 4h were significantly higher than those of the control,while the node position of the first female flowers was lower than that of the control,with no significant difference,and the plant height increased by 10.43 cm compared with the control.An increase of 9.28%;Stem diameter increased by 2.06 mm and 30.16% compared with the control.Compared with the control,the number of leaves increased by 1.33 and 8.81%.Compared with the control,the maximum leaf area increased by 24.60%(64.93cm2).The node position of the first female flower decreased by 0.24 nodes(6.54%)compared with the control.The number of female flowers in 10 nodes increased by 0.60,28.57% compared with the control.The number of female flowers from 10 to 20 nodes increased by 0.90 and 33.33% compared with the control group.The average melon weight per plant,melon number per plant,melon weight per plant,melon number in plot,plot yield and converted per mu yield of all treatments were higher than those of the control.The average melon weight per plant,plot yield and converted per mu yield of all treatments were significantly higher than those of the control at 70℃ for2 h,4h,6h and 10 h.The average melon weight increased by 17.50g(11.06%)at 70℃ for4 h compared with the control.The average number of melons per plant increased by 0.47 and 6.83% compared with the control.The average melon weight per plant increased by191.41 g and 17.64% compared with the control.The number of melons in the plot increased by 12,6.70%,compared with the control.The yield of plot increased by 5.31 Kg and 18.22% compared with that of control.The yield per mu increased by 494.51 Kg and18.22% compared with the control.4.The disease index of field experiment: in the field investigation of cucumber powdery mildew,the onset of powdery mildew at 70℃ for 4h and 80℃ for 4h was 3 days later than that of the control.In the last investigation,the diseased plant rate,diseased leaf rate and disease index of each treatment were lower than those of the control.The diseased plant rate,diseased leaf rate and disease index of the treatment at 70℃ for 4h were significantly lower than those of the control and other treatments,and the diseased plant rate,diseased leaf rate and disease index were 36.67%,21.68% and 15.73% lower than those of the control,respectively.In the field investigation of cucumber downy mildew,the onset of cucumber downy mildew at 70℃ for 2h,6h,8h,10 h and 80℃ for 4h was 3 days later than the control,and the onset of cucumber downy mildew at 70℃ for 4h was 6 days later than the control.In the last investigation,the diseased plant rate,diseased leaf rate and disease index of each treatment were lower than those of the control.The diseased plant rate,diseased leaf rate and disease index of the treatment at 70℃ for 4h were significantly lower than those of the control and other treatments,and the diseased plant rate,diseased leaf rate and disease index were 16.67%,10.36% and 5.56% lower than those of the control,respectively.In the field investigation of cucumber horn spot disease,the onset of cucumber horn spot disease at 80℃ for 6h was 3 days later than the control,and the onset of cucumber horn spot disease at 70℃ for 4h,10 h and 80℃ for 4h was 6 days later than the control.In the last investigation,the diseased plant rate,diseased leaf rate and disease index of each treatment were significantly lower than those of the control.The diseased plant rate,diseased leaf rate and disease index of the treatment at 70℃ for 4h were lower than those of other treatments,and the diseased plant rate,diseased leaf rate and disease index were30.00%,7.18% and 4.68% lower than those of the control,respectively.In conclusion,the germination index of cucumber seeds under dry heat treatment for4 h at 70℃ was the best.The inactivation rate of fungal and bacterial seed-borne pathogens was significantly higher than that of control.The growth and development indexes of cucumber plants were the best after field planting.The morbidity of cucumber powdery mildew was 3d later than that of the control,the morbidity of cucumber downy mildew was 6d later than that of the control,and the morbidity of cucumber horn spot disease was6 d later than that of the control.The morbidity of cucumber powdery mildew,cucumber downy mildew and cucumber horn spot disease were lower than that of the control and other treatments. |
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