by Many gardeners are used to collecting tomato seeds themselves. It is simple and convenient: in the spring you do not need to waste time looking for the necessary seeds. And if the variety is rare or is no longer available for sale, then you need to try very hard to save it and collect seeds from your fruits. But what if the tomatoes start to get sick?
Of course, it is very undesirable to take fruits from diseased bushes for seeds: after all, we know that many tomato diseases are transmitted with seed material (this mostly concerns viral and bacterial infections). But it often happens that after the first manifestations the disease is stopped, the bushes are treated, the diseased parts of the plants are removed, and the fruits subsequently ripen and look absolutely healthy.
It is especially important to act quickly at the first signs of late blight. This disease develops so rapidly that in a few rainy days it can lead to the complete death of the bushes. Then, of course, there can be no talk of any healthy fruits.
How Tomatoes Get Infected with Late Blight
The causative agents of tomato late blight are oomycetes Phytophthora infestans, occupying an intermediate position between algae and fungi. The vegetative body of this phytopathogen is a well-developed non-cellular mycelium that grows in the cells and intercellular fluid of the plant.
During asexual reproduction on the underside of leaves, the phytopathogen appears as sporangiophores with lemon-shaped zoosporangia, which are carried around the area by splashes of water and wind. When a zoosporangium falls into a drop of water, it splits, resulting in the formation of 6-8 mobile zoospores, which actively move in the water with the help of flagella. Each zoospore subsequently germinates with a germ tube and penetrates into the tissue of the leaf or fruit through the stoma. Under favorable conditions (humidity above 75% and temperature 10-20°C), the time from infection to new sporulation is only 3-4 days. At elevated temperatures (above 20°C), zoospores are not formed, and the zoosporangium germinates entirely, as a single spore – a conidium.
The release of zoospores from zoosporangia, their germination and infection can only occur in the presence of water falling on plants as a result of rain or fog – in dry air, the spores die after 2-3 hours. Air temperature is also of significant importance: at temperatures above 26°C, the viability of spores decreases, and at 30°C, the development of late blight stops.
In addition to asexual reproduction, Phytophthora infestans a sexual process is possible, resulting in the formation of oospores, which have a dense shell and are capable of surviving for a long time in the soil, on plant residues and seeds of infected plants. Under favorable conditions, oospores are the source of primary reproduction and germinate into zoosporangia with zoospores. Oospores are capable of withstanding temperatures above 40°C for 12 hours, and 46°C for up to two hours. So after heating for two hours at a temperature of 46-50°C, the seeds can be considered disinfected from late blight.
The most favorable conditions for the development of the disease:
- high humidity;
- large difference between day and night temperatures;
- poor air circulation;
- moderate air temperature (10-20°C).
How to stop the development of late blight
At the first signs of the disease (dark brown spots on the lower leaves with light green edges), it is necessary to take action quickly:
- Cut off all affected parts of plants. Remove plants with significant stem and leaf damage completely.
- After removing diseased parts of tomatoes, treat the tools with an antiseptic.
- Cut off side shoots and tops of shoots that thicken the bushes and interfere with air circulation.
- Provide ventilation for the greenhouse or hotbed.
- Treat the bushes with fungicides based on azoxystrobin or mandipropamid (Provisor, Revus). Among biological preparations, the most effective are those based on the soil fungus Trichoderma (Trichoderma Veride, Trichoplant, etc.), which should be used not only for treating the bushes, but also for improving the soil.
You cannot leave parts of plants affected by late blight in the garden bed or put them in the composter – this will lead to the spread of the infection throughout the area.
What fruits can be taken for seeds?
Let’s assume that the disease has been stopped, the bushes continue to develop, the fruits ripen on them and healthy shoots grow. For seeds, you can take tomatoes that have ripened on the bushes without signs of late blight or any other infection. Select the largest fruits, wash them, blot them with a napkin and put them for one or two weeks to ripen until the fruits become slightly soft.
If tomatoes are infected with late blight, the disease will appear in a few days. Therefore, you should periodically inspect the fruits and remove those that show signs of the disease.
How to collect seeds and ferment
The day before collecting the seeds, wash the fruits again and dry them. Extract the seeds together with the juice in which they will ferment. Fermentation will disinfect the seed material and destroy the mucous membrane around the seed, which will facilitate germination in the future.
After extracting the seeds from all the prepared fruits, add a few drops of liquid Fitosporin-M or another preparation based on hay bacillus, which is suitable for soaking and disinfecting the seed material, to the container with the pulp. The hay bacillus will help to cope with the infection already at the fermentation stage, while the seed shell is soft.
After adding the hay bacillus preparation, place the pulp with seeds in a dark place to ferment for several days. Stir the contents of the container from time to time. And after the seeds have settled to the bottom, rinse and dry them, laying them out in a sunny place.
How can you disinfect seeds before sowing?
If you did not disinfect the seeds during fermentation or, say, someone shared their seeds with you, they need to be disinfected before sowing, as they may be populated with various phytopathogens. What can be used to disinfect seeds?
- Biological preparations based on hay bacillus, trichoderma or pseudomonads (Fitosporin-M, Trichoderma Veride, Trichoplant, Sporobacterin, Ekomik Urozhainy, etc.). Beneficial microorganisms of biological preparations, settling on the surface of seeds, protect them from the effects of various phytopathogens, increase germination and strengthen the immunity of future plants.
- Pharmaceutical preparations: chlorhexidine bigluconate, hydrogen peroxide (3% solution), potassium permanganate (1% solution). The seeds are kept in these solutions for 15-20 minutes, and then washed with running water.
- Folk remedies:
Infusion of garlic. Chop 3-4 cloves of garlic (20 g), pour in water (100 ml), cover and leave for at least 2 hours. Soak tomato seeds in the infusion for 30 minutes, then rinse them with running water.
Aloe juice. Cut off the lower leaves of an aloe plant that is at least three years old, wash them, dry them and put them in the refrigerator for 10-14 days. Then squeeze out the juice and dilute it in a 1:1 ratio with water. Place the seeds in the solution and leave for six hours. Since aloe juice is not only a disinfectant but also a growth stimulant, old tomato seeds can be soaked in undiluted aloe juice – this will improve their germination.
Turmeric infusion. At least a day before seed treatment, prepare an extract: pour 5 g of turmeric powder and a pinch of ground black pepper into 100 ml of vodka or alcohol. To disinfect the seeds, dilute 5 ml of the extract in 200 ml of water. Keep the seeds in the solution for 6-12 hours.
Healthy seed material does not guarantee that tomatoes will not get sick in the next season, since phytopathogens can be in the soil and overwinter on plant debris. Therefore, special attention should be paid to the treatment of the soil, greenhouse and garden tools, especially if the bushes were sick with late blight or something else.
