Jie XU, Wenting ZHU, Li SUN

1. Zaozhuang Academy of Agricultural Sciences, Zaozhuang 277899, China; 2. Zaozhuang Denghai Detai Seed Industry Co., Ltd., Zaozhuang 277116, China; 3. Zaozhuang Cotton Original Seed Breeding Plant, Zaozhuang 277300, China

Abstract In recent years, potato soil-borne diseases have occurred severely. The investigation shows that potato Fusarium wilt greatly affects potato yield, leading to a yield reduction rate of 21.8%. Potato powdery scab shows very mild symptoms on potato tuber, basically with no symptoms in some plots, but shows obvious symptoms on the root system. A large number of nodules which are produced on one side of the root system seriously affect water and fertilizer absorption function of the potato root system. Potato tubers expand slowly, leading to small potato tuber, low yield and low commodity rate. The fungus can survive in soil for more than 10 years. Potato soil-borne diseases are harmful and are difficult to control. Susceptible plants can be detected by high definition chromatographic control method and pathogen detection. For prevention and control of potato soil-borne diseases, first of all, disease-resistant varieties should be chosen and virus-free potato seeds are used for sowing. Secondly, metham and dazomet can be used to treat soil in order to prevent and control potato soil-borne diseases. The results showed that the dead seedling rate treated by metham was reduced from 35% to 12.5% compared with the blank control, and the yield was increased by 44.09 kg/ha, with an increase rate of 18.2%. Compared with the blank control, the dead seedling rate treated by dazomet was decreased from 35% to 7.5%, and the yield was increased by 38.10 kg/ha, with an increase rate of 15.7%. The soil treatment received obvious yield increase effect.

Key words Potato, Soil-borne disease, Prevention and control

1 Introduction

Zaozhuang is an old potato planting area. As of the end of 2019, the potato planting area of Zaozhuang has grown to about 56 700 ha, with a total output value of 1.75 million yuan. Because potatoes are grown all year round, soil-borne diseases occur severely. For example,Verticilliumwilt, tarspot, black shank,Fusariumwilt, scab, powdery scab occur from time to time, with the incidence area getting bigger and bigger and the incidence getting heavier and heavier. Soil-borne diseases are caused by the infection of soil-borne pathogens, including fungi, bacteria, actinomycetes, nematodes,etc.Soil-borne diseases can lead to a large reduction in potato yield, and even plant death, resulting in crop failure and greatly affecting farmers’ income. Therefore, the application of prevention and control technology against soil-borne diseases can effectively prevent the occurrence of soil-borne diseases, reduce farmers’ losses and improve farmers’ income.

2 Investigation of potato soil-borne diseases

PotatoFusariumwilt, potato tarspot, potato scab and potato powdery scab were specially investigated by members of Zaozhuang comprehensive experimental station of potato industry system from May 6 to 8, 2020.

The survey results showed that potatoFusariumwilt had great impact on potato yield, and the yield reduction rate reached 21.8%. Potato powdery scab showed very mild symptoms on potato tuber, basically with no symptoms in some plots, but showed obvious symptoms on the root system. A large number of nodules which were produced on one side of the root system seriously affected water and fertilizer absorption function of the potato root system. Potato tubers expanded slowly, leading to small potato tuber, low yield and low commodity rate. The fungus can survive in soil for more than 10 years.

Due to heavy damage and difficulties in prevention and control, potato soil-borne diseases, especially potatoFusariumwilt and powdery scab, have become the main diseases that harm potato industry in Zaozhuang City.

3 Detection technique of potato soil-borne diseases

3.1 High definition chromatographic control methodSoil-borne diseases, such as scab and black shank, can be easily detected by comparing high definition chromatogram with real potato.

Potato scab mainly harms tubers. When tubers are infected, light brown small projections are produced in the epidermis, which gradually expand and suberize with rough surface. Later, raised or sunken scab-like hard plaques are formed on spot surface. The lesions are confined to the epidermis and do not penetrate into the potato.

Potato black shank mainly infects the stem and tuber, which occurs from seedling stage to growth stage. Most plants that are infected by black shank will lose water and droop, with leaves rolling up but no changes in color as well as dark brown rot in black shank part, and the whole plant wilts.

The incidence at the seedling stage will lead to dwarf plants, shortened internodes, roll-up leaves, chlorotic leaves, black rot tissue at stem base, wilting plant, and no tuberization.

The onset of tuber starts from umbilical region which is dark brown, rotten and stinking, and then extends a few centimeters above the stem or to the entire stem. The lesions are dark brown, and the vascular bundle is dark brown in cross section.

3.2 Pathogen detection

3.2.1Detection of the pathogen causing potato scab. Potato scab is a serious economic disease caused by the pathogensStreptomycesscabies,Streptomycesacidiscabies,etc., which are transmitted by seed or soil. With the increase of planting years, the morbidity risk rate of scab increases year by year, and the harm of scab becomes more and more serious[1].

The soil in the arable layer was detected by bioelectrochemical method, microcolony technology and gas chromatography to check the presence ofStreptomycessp. and to further determine the infection of potato scab.

3.2.2Detection of the pathogen causing potato black shank. Potato black shank is caused by the infection ofErwiniacarotovora. Potato black shank causes serious harms and can lead to a significant reduction in potato yield.

It is possible to determine whether potato plants are infected by black shank by testing the soil in the arable layer and fungus-carrying information of potato seed.

4 Selection of potato seed

4.1 Selection of disease-resistant varietiesAlthough potato soil-borne diseases occur severely, the selection of disease-resistant potato varieties can effectively control potato soil-borne diseases,e.g., Kangyi 1, Shengli 1.

4.2 Application of virus-free potato seedVirus-free potato seed is the original potato seed without pathogenic fungi. The virus-free potato seed can be obtained through stem tip stripping, virus-free seedlings propagation, indoor breeding of breeder’s seed and breeding of potato seed under a series of isolation conditions. The use of miniature whole potato will also reduce the chance of pathogen infection, which greatly reduces the occurrence of pathogen soil-borne diseases.

5 Integrated prevention and control of potato soil-borne diseases

5.1 MaterialsThe potato variety, Favorita, was used in the test. The plots severely attacked by potatoVerticilliumwilt in the past year were selected as the plots to be tested.

5.2 Methods

5.2.1Prevention and control of potato soil-borne diseases by metham soil treatment. The crop plants and weeds in the field were removed. To prevent secondary infection of farm manure, the farm manure needed for potato growth was applied before pesticide administration. Subsequently, the soil was loosened by plowing, and ditches were opened in the field, with a depth of 15-20 cm and a space of 20-25 cm. Metham 100 times dilution was administrated evenly at the dose of 300 kg/ha, and the soil was covered immediately. The field was watered appropriately based on soil moisture content, making the soil humidity reaching 65%-75%. The plastic film was covered immediately to prevent the volatilization of pesticide.

After administration, the field was fumigated in a closed environment for more than 15 d. When the film was removed, the soil was deeply ploughed on the same day to loose the soil and the air was dispersed for 5-7 d. After the air was cleared, potatoes could be sown. The occurrence of potato soil-borne diseases was observed and recorded, and the experimental data were analyzed and summarized[2].

The plot covered an area of 12.6 m2, with a row spacing of 0.63 m, and a plant spacing of 0.25 m.

5.2.2Prevention and control of potato soil-borne diseases by dazomet soil treatment. The crop plants and weeds in the field were removed. To prevent secondary infection of farm manure, the farm manure needed for potato growth was applied before pesticide administration. The soil was irrigated with water to maintain the soil moisture content at 60%-70% for 3-5 d. Dazomet was broadcasted evenly at the dose of 450 kg/ha, and the soil was deeply ploughed with a rotary cultivator to a depth of 30 cm, making the pesticide fully contact with soil particles. Afterwards, the field was covered with plastic film, and the joint of plastic film was sealed by furrow pressing method, leaving no dead angle.

After administration, the field was fumigated in a closed environment for more than 20 d. The soil was deeply ploughed to a depth of 30 cm on the same day to loose the soil, and the air was dispersed for 15 d. After the air was cleared, potatoes could be sown. The soil was finely raked before sowing and applied with fungicide. The occurrence of potato soil-borne diseases was observed and recorded, and the experimental data were analyzed and summarized[3].

The plot covered an area of 12.6 m2, with a row spacing of 0.63 m, and a plant spacing of 0.25 m.

5.3 Results and analysis

5.3.1Prevention and control results of potato soil-borne diseases by metham soil treatment. The results (Table 2) showed that the dead seedlings in potato plots treated by metham decreased significantly, and the dead seedling rate decreased from 35% to 12.5% compared to the blank control. Meantime, the yield increased significantly, with an increase of 44.09 kg/ha and an increase rate of 18.2%.

Table 1 Survey of potato soil-borne diseases

5.3.2Prevention and control results of potato soil-borne diseases by dazomet soil treatment. The results (Table 3) showed that the dead seedlings in potato plots treated by dazomet decreased significantly, and the dead seedling rate decreased from 35% to 7.5% compared to the blank control. Meantime, the yield increased significantly, with an increase of 38.10 kg/ha and an increase rate of 15.7%.

Table 2 Experimental data of prevention and control of potato soil-borne diseases by metham soil treatment

Table 3 Experimental data of prevention and control of potato soil-borne diseases by dazomet soil treatment

6 Conclusions and discussion

The experimental results showed that metham and dazomet treatment had obvious control effect on potato soil-borne diseases. Compared with the blank control, the dead seedling rate treated by metham decreased from 35% to 12.5%, and the yield increased by 44.09 kg/ha with an increase rate of 18.2%. Compared with the blank control, the dead seedling rate treated by dazomet decreased from 35% to 7.5%, and the yield increased by 38.10 kg/ha with an increase rate of 15.7%.