Management techniques for grafted tomato seedlings in high altitude areas

Management techniques for grafted tomato seedlings in high altitude areas

With the development of agriculture, the planting area of ​​tomatoes continues to expand, and vegetable farmers plant crops continuously all year round. Coupled with problems such as extensive management, backward technology, and irregular use of pesticides and fertilizers, the problem of soil-borne diseases has become increasingly prominent. This article combines the actual local conditions and summarizes the management technology of tomato grafting and seedling breeding in high-altitude areas from aspects such as facility environmental treatment, rootstock and scion variety selection, sowing management, grafting management, and pest control, etc., aiming to provide reference for relevant practitioners.
Keywords: high altitude; grafting and seedling raising; tomato grafting; seedling raising management.

Seedling facilities, equipment and raw materials
Intensive plug seedling cultivation should be carried out in a greenhouse, supplemented by shading and cooling systems in the high temperature seasons of summer and autumn, and heating and lighting equipment in the low temperature seasons of winter and spring [2]. A 40- to 60-mesh silver-gray insect-proof net is installed at the air outlet of the greenhouse. A buffer room is set up at the entrance and exit and a 40- to 60-mesh silver-gray insect-proof net is installed. According to the structure and size of the greenhouse, a mobile or fixed seedling bed of appropriate size is installed. The irrigation system is divided into two types: a self-propelled irrigation system and a manual irrigation system. Infrastructure such as mechanical transportation and pedestrian passages, drainage systems, and emergency power supply systems are also reasonably configured. Facilities such as planters, germination rooms, and healing rooms are flexibly selected according to actual conditions. Before starting the seedling cultivation work, prepare the substrate, plug trays, seedling fertilizer, pesticides, mulch and other materials required for seedling cultivation, and ensure the normal use of water and electricity.

Greenhouse environmental treatment
Before the start of each season's seedling production, in order to eliminate residual germs and insect eggs in the greenhouse, the seedling greenhouse needs to be disinfected. KMnO4 1.65 kg, CH2O 1.65 L, and boiling water 8.4 kg per acre are used for disinfection. CH2O is added to the boiling water, and then Add KMnO4 to produce a smoke reaction. Note that there are no less than 4 reaction points. You can also use finished sterilizing and insecticidal aerosols, ignite them to produce smoke, first seal and fumigate for 48 hours for disinfection, and then continue to ventilate them until the smell has dissipated before use. Key production areas such as the mixing yard and germination room should be sprayed and sterilized with 2000 times of KMnO4 or 800 times of 40% chlorothalonil suspension.

Grafting rootstock and scion selection
As the number of grafted tomato seedlings increases, more and more varieties of tomato rootstocks are commercialized on the market, with outstanding characteristics such as affinity, disease resistance, stress resistance and adaptability. Among them, Shanghai Huihe Seed Industry's '405' tomato rootstock, Japan's Sakata Seeds '150 Tomato' rootstock, Shouguang Vegetable Seed Group's 'Zhiyumi Tomato' rootstock are available for selection. The selection of scions is based on the main market varieties, product requirements, planting stubble and disease resistance requirements in the planting area.

sowing work
Sowing period
With the changes in climate conditions in different seasons, the sowing period and sowing interval of rootstocks and scions change greatly. The sowing time in winter and spring low-temperature seasons should be carried out 50 to 60 days earlier than the planting time; the sowing time in summer and autumn high-temperature seasons should be carried out 50 to 60 days earlier than the planting time. It is better to do it 25 to 30 days in advance. According to the characteristics of the rootstock and scion varieties, if the growth period of the rootstock is longer than that of the scion, the rootstock should be sown 5 to 10 days in advance; if the growth period of the rootstock and scion are basically the same, the rootstock and scion should be sown at the same time; if the growth period of the scion is longer than that of the stock, the scion should be sown 5 days in advance. ~10 days to sow
Substrate Selection and Treatment Tomato seedling cultivation substrate generally chooses 200 L of imported peat soil per bag and 100 L of perlite mixed in a ratio of 1:2. Substrates that are self-prepared or reused should be disinfected, and 68% caustic acid should be added to each cubic meter of substrate. Mix evenly with 0.2 kg of mold·thiram wettable powder or 0.1 kg of 70% thiophanate methyl wettable powder. After the substrate is prepared, put it into a 72-hole plug tray, scrape it flat and wait for sowing.
Seed Treatment Regularly packaged seeds on the market are generally screened, coated and sterilized before leaving the factory, and can be sown directly without separate treatment. Untreated seeds are generally heat treated using a simple and practical method. Soak the seeds in clean water for 8 to 12 minutes to remove deflated seeds and impurities. Then soak the seeds in warm water of 55 to 58°C for 15 to 20 minutes. Stir continuously during the period. When the water temperature drops to about 32°C, soak for 6 hours. Remove the seeds and dry them before sowing.
Sowing methods: Sowing methods are divided into manual sowing and mechanical sowing. If the degree of mechanized management is low, manual seeding should be used when using germinated seeds or small batches of seedlings. When using ungerminated seeds in large batches, it is better to choose more efficient mechanical seeding.
Artificial sowing is to use a hole punch or suitable tool in the center of the hole tray with the substrate installed to drill a hole with a depth of 0.5 to 1.0 cm in the center of the hole. One seed is placed in each hole. After sowing, it is covered with perlite or vermiculite. Then the substrate is smoothed. After the sowing process is completed, place the plug tray neatly on the seedbed and water it. The first watering must be done thoroughly. Intensive seedlings should be installed with self-propelled or manual irrigation systems for watering. Mechanical sowing is to use a seeder to automatically sow
The working parameters of the seeding machinery are adjusted according to the requirements of seed size, plug tray specifications, sowing depth, watering amount and watering method. The seeder automatically completes substrate loading and scraping, drilling holes, seed sowing, vermiculite covering and seedbed watering. Water and other procedures. When sowing, personnel need to be arranged to conduct inspections to avoid missed or multi-sowed seeds. Materials should be replenished in a timely manner to remove the sown plug trays. After the sowing process is completed, the plug trays should be arranged neatly and orderly on the seedbed. Seeds that have been germinated are not suitable for mechanical sowing.

Seedling management
After sowing is completed, temperature control management should be carried out in seedling facilities such as solar greenhouses, multi-span greenhouses and plastic greenhouses. The daytime temperature before germination and emergence is 28-30°C, and the night-time temperature is 15-20°C. When about 80% of the rootstock or scion seedlings are exposed to the substrate, gradually manage the temperature from high to low. The daytime temperature is 20-25°C and the night-time temperature is 13-16°C to prevent the seedlings from growing too much.
In high-temperature seasons, you can choose to take measures such as opening the greenhouse air vents, activating the sunshade system, and using a greenhouse cooling system to reduce the temperature in the greenhouse; in low-temperature seasons, you can take measures such as reducing the size and ventilation time of the air vents, adding insulation quilts in a timely manner, and activating temporary heating systems. Take other measures to increase the temperature in the greenhouse. When the weather continues to be cloudy and rainy for more than 5 days, the supplementary light system can be used to supplement the light.
In order to shorten the germination time and ensure neat emergence, the seeds can also be germinated in plug trays after sowing. If there is a germination room, it is advisable to germinate in the germination room, and the room temperature should be controlled at 25-30°C. If there is no germination room, place the plug trays on the seedbed, cover it with a layer of mulch film to moisturize, add a layer of non-woven fabric on the film, and control the temperature at 25-30°C. When more than 5% of the seedlings are exposed to the substrate, remove the mulch film and non-woven fabric covering the plug tray. During tomato germination, the plug trays should be inspected 2 to 3 times a day to observe the matrix moisture and seed germination conditions in the plug trays, and randomly select 3 to 5 plug trays each time. Adjust the plug position and seedbed temperature in a timely manner according to the inspection situation.
The relative moisture content of the matrix should be maintained at 70% to 85% from the stage of seed germination to the seedlings exposing the matrix; from the cotyledon expansion to the 2 leaves and 1 heart stage, the relative moisture content of the matrix should be 65% to 75%; from the stage of seedlings with 2 leaves and 1 heart to the emergence of the seedlings, the relative moisture content of the matrix should be maintained at 70% to 85%. Moisture content 70% to 90%. The air humidity in facilities such as solar greenhouses, multi-span greenhouses and plastic greenhouses should be maintained at 60% to 75%.
After the rootstock and scion cotyledons are fully expanded, fertilizers should be flushed with water. Using nitrogen fertilizer concentration as a reference index, the concentration should be 55 to 75 mg/kg. Fertilize 2 to 3 times every 7 days before the seedlings have one leaf and one heart; before the seedlings have one leaf and one heart, the nitrogen fertilizer concentration should be 90 to 120 mg/kg, and fertilization should be done in water. It is advisable to choose N-P-K=20-10-20 macroelement water-soluble fertilizer and N-P-K=17-4-17 macroelement water-soluble fertilizer to be applied alternately. If necessary, add water-soluble fertilizers such as amino acids and humic acid. It is recommended to choose a regular brand of special fertilizer for tomato seedlings. In high-temperature seasons, watering frequency is high, and the fertilizer application concentration should be low. In low-temperature seasons, watering frequency is low, and fertilizer application concentration should be appropriately increased.

Grafting management
Preparation before grafting
Before grafting, the rootstocks should be screened in advance to select weak seedlings and small seedlings, so that the sizes of the rootstocks in each tray are basically the same. If the artificial conditions of the scions permit, they can also be screened according to the same standards. When the rootstock seedlings (3 to 5) have 1 heart of leaves The suitable period for grafting is when the scion seedlings (2 to 4) have one leaf and the stem diameter of the rootstock and scion reaches 3 to 4 mm. One day before grafting, water both the rootstock and scion so that the moisture content of the substrate reaches more than 80%. Ensure that grafting is completed without watering for 2 to 3 days, and spray a comprehensive insecticide and fungicide once. Choose to avoid strong light and graft under shading conditions.
Grafting method 6.2.1 For the pasting method, select a casing with a length of 1.2 to 1.5 cm. The inner diameter of the casing should match the diameter of the rootstock and scion incision. The rootstock should be kept 1.0 to 1.5 cm above the cotyledons, and below the growth point of the scion, which is the same or close to the diameter of the cutting part of the rootstock. Use a blade to cut off the rootstock and scion at a 45° angle. First insert the casing from the top of the rootstock and put it on the rootstock. At the incision site, insert the scion into the casing from the top, so that the cut surfaces of the stock and scion are closely connected, and be careful to clamp them firmly to prevent the scion from slipping. After grafting, the entire tray of seedlings should be immediately placed on the seedbed. All plug trays should be arranged in the same manner, and should be covered with a film to moisturize in time to prevent excessive water loss of the scion.
6.2.2 Split grafting method: Leave 4 to 5 cm of the rootstock stem from bottom to top, cut it flat with a blade to remove the growing point, use the blade to cut vertically downward in the middle of the stem, and cut the joint about 1 cm lengthwise. Cut off the scion horizontally below the 2nd to 3rd true leaves at a point with the same or similar diameter to the rootstock interface, and cut the incision into a wedge shape of about 1 cm. Insert the scion into the rootstock interface and align it so that the rootstock interface and the scion incision are completely tight, and secure them firmly with a special tomato grafting clip. Other operation methods are consistent with the bonding method.
Management after grafting After grafting is completed, cover the seedlings with plastic film and press tightly around them to seal the seedbed. It is not advisable to let the air out for the first 3 days, and the air humidity should be kept at 85% to 90%. In case of high temperature weather, the film can be appropriately removed for ventilation. Due to strong ultraviolet rays and low air humidity in Tibet, high-pressure mist spray equipment can be installed to ensure air humidity.
Or use a sprayer to spray at the bottom and around the seedbed from time to time to ensure that the air humidity is within the appropriate range; 3 to 5 days after grafting, remove the film at the right time in the morning to ventilate, and restore the film in time to prevent the air humidity from dissipating too quickly. The air outlet increases from small to large, and the air release time increases from short When the plant grows, gradually increase the ventilation volume and air release time, and sprinkle water appropriately during the period to ensure the normal needs of the seedlings and improve the survival rate; in 6 to 8 days, the rootstock and the xylem of the scion junction will be completely integrated, and the grafted seedlings will no longer wilt. Remove the plastic film and return to normal management
In the early stage of grafting, the temperature in the facility must be strictly controlled. Hang a thermometer or other temperature detection equipment about 10 cm above the seedlings. The daytime temperature is maintained at 24-30°C and the night-time temperature is 18-22°C. After grafting, the daytime temperature is 22-28°C and the night-time temperature is 16-20°C. The night temperature should be appropriately lowered before the grafted seedlings leave the nursery to increase the temperature difference between day and night.
Excessive light will cause the temperature under the film to be too high, which can easily cause diseases such as yellow leaves or rotten leaves on seedlings. Under normal lighting conditions, the outside of a solar greenhouse, multi-span greenhouse or plastic greenhouse should be covered with a shading rate of 75% to 80%. Black or silver-gray sunshade nets should be used to cover the internal sunshade inside the facility during high temperature seasons, and cooling facilities such as fans and wet curtains should be turned on to ensure that the temperature is within a suitable range.
For the first 3 to 4 days, it is advisable to cover the sunshade net all day long on sunny days, and only cover it with a film on rainy days. After that, gradually increase the exposure time between 08:00-10:00 and 16:00-18:00, and shorten the noon shading time. Until the sunshade net is completely removed. When the grafting interface of the grafted tomato seedlings is completely healed and the heart leaves begin to grow, switch to normal fertilizer and water management. Depending on the substrate moisture and weather conditions, water once every 2 to 3 days, and fertilize with the water. Apply fertilizer concentration within the range of 1 to 2 g/kg.

Pest and disease control
Common diseases and insect pests during intensive plug grafting and seedling cultivation of tomatoes include damping-off, blight, blight, viral diseases, whiteflies, aphids, thrips, etc. Give priority to agricultural control, physical control, and biological control, and when necessary, use low-toxicity and low-residue chemical pesticides accurately to carry out green prevention and control. Hang yellow or blue armyworm boards in solar greenhouses, multi-span greenhouses or plastic greenhouses, inoculate plant growth-promoting rhizosphere bacteria into the seedling medium, and spray plant or biological agents such as anisate, nicotine, and rotenone to prevent pests and diseases.
Spray once every 5 to 10 days after emergence, and alternately use 50% dimethomorph suspension, 58% armor frost·manganese zinc wettable powder, and 12% copper rosinate suspension to prevent damping-off and blight. To treat disease and late blight, use 25-30 mL, 80-100 g, 150-175 g water spray per acre respectively. Pests such as aphids and whiteflies can be controlled by spraying 15-20 g of 20% flonicamid water-dispersible granules per acre mixed with water when the pest rate reaches 0.5%.

Seedling standard
The healing rate of the grafting interface of tomato grafted seedlings reaches over 95%. The plant height is 10-15 cm, the stem thickness is 4-6 mm, and the plant shape should be uniform. Leaves (3 to 4) have one core, and the leaf age consistency rate should be greater than 90%; the leaf color is the inherent green color of the selected variety, and there are no obvious symptoms of pests and diseases; the root system has many white roots and is well developed, and tightly wraps the substrate, so as to When the root is pulled up in the hole tray, the root lump will be formed and the lump will not be scattered. In order to make the seedlings better adapt to the planting environment, the seedlings can be properly trained before leaving the nursery. The main measures include increasing ventilation, lowering the temperature in the facility, reducing the amount of watering, increasing light intensity and time, and increasing the spacing between plug trays.