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Video: Harvest Components: Resistance Of Varieties And Hybrids To Various Diseases
Read the previous part. ← Harvest components: the use of biostimulants
Seed varieties, hybrids
Let's talk about seed varieties. First of all, I want to say that, in my opinion, in our climatic conditions it is more rational to use heterotic F 1 hybrids for sowing. Once upon a time, gardeners had already noticed that varieties were degenerating, and resorted to various tricks to preserve the properties of the variety.
I will cite an excerpt from an old magazine: “The germination ability of cucumber seeds lasts even up to 10 years; but seeds that are three to five years old are considered the best for sowing. This ability of cucumbers to maintain germination for many years makes it possible for seed growers to breed several varieties of seeds without fear of their degeneration or mixing; for this, only one variety should be bred for seeds in one year. The stock of seeds from each year is made such that it would last for several years, and in this way it is possible to have clean seeds of different varieties, albeit from different years”(“Village”, 1885, No. 2)
Now breeders have learned how to create heterotic hybrids, which has solved a lot of problems. When creating heterotic hybrids, the selection of parental lines is carried out on several grounds.
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Therefore, the ability of such plants to withstand temperature extremes, pests and diseases, to give stable yields in any abnormal summer is much higher than that of traditional varieties. The resistance of F1 hybrids to diseases, due to the combination of the traits of the two parental lines, is always higher than that of conventional varieties.
Before talking about specific hybrids, I want to say a few words about the "popular" diseases of vegetables to which the hybrids are resistant. These are:
Verticillium dahliae (Va) - the causative agent of verticillium wilting.
Fusarium oxysporum f.sp.licopercici (Fol) is the causative agent of fusarium wilt.
Cladosporium fulvum (Ff) Cladosporium cucumerinum (Ccu) - cladosporium or brown leaf spot of tomato. Cladosporium or olive spot of cucumber, squash.
I will not bore you with tragic pictures from the life of vegetables, I think that sometimes you met with them in your garden practice. I will just list the short designations of diseases, which are usually written on a bag of seeds, using the example of tomato and cucumber. It is clear that other types of vegetables are also affected by diseases, it is also clear that there are hybrids resistant to certain diseases in their groups.
But everything is not so simple, because pathogenic bacteria mutate, forming new strains, to which there may be a hybrid and unstable. New stable hybrids appear - there is a competition between breeders and pathogens. And also the whims of nature add their own component. So try to select resistant hybrids based on your conditions. For example, recently the nematode "raged", and only stable hybrids withstood its pressure and were recommended for planting.
And if we talk about cucumbers, then powdery and downy mildew destroyed many ancient varieties. It is difficult to determine a specific disease in appearance, even for a specialist, expensive studies are needed, and the gardener should not delve into these subtleties. Try to look after the plants and plant the right hybrids, then the weather will be favorable for you.
For example, I will list the short designations of diseases that are usually written on a bag when characterizing the resistance of a hybrid.
Wi - silvery leaves.
TSWV - tomato bronze.
TYLCV - yellow curling of tomato leaves.
ToMV - tomato mosaic.
Ff - brown (olive) spot.
Рс - late blight.
Fol - Fusarium wilting.
For - Fusarium root rot.
Lt - powdery mildew.
On - downy mildew.
Va - Verticillium albo-atrum - Verticillium wilting.
Vd -Verticillium dahliae - verticillary wilting.
Ma - Meloidogyne arenaria - nematode.
Mi-Meloidogyne incognita - nematode.
Mj - Meloidogyne javanica - nematode
CMV is a common cucumber mosaic.
CVYV - yellowing of cucumber vessels.
ZYMV - yellow mosaic.
Ccu - cladosporium or olive spot.
Cca - leaf spot.
Sf - powdery mildew. Sometimes, the designations change, but you can use the reference literature.
The result largely depends on the realization of the genetic potential of the productivity of the variety, on the extent to which this is possible in the specific conditions of the culture. In this regard, it is very important to know the ecological parameters of the variety, its adaptive capabilities when changing the intensity of manifestation of environmental factors. It is also a reaction to temperature: the temperature range of the crop. Reaction to the transition from low to high temperatures and, conversely, a reaction to night temperatures of air and soil.
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Here are the important hybrid metrics:
The early maturity of the hybrid is determined by the biologically active temperature (BAP). This is the minimum temperature at which a particular plant species grows. Knowing this important parameter, it is possible to roughly determine whether this or that variety will grow in a given area, and how the microclimate of the site, its instability, will affect its growth and development. It is necessary to know the heat requirements of the hybrid for full maturation and fruiting.
In some years, it is impossible to count on yields from mid-season and late varieties in our climatic zone, therefore it is safer to use early-maturing hybrids. Let me give you an example. At + 15 ° C, seeds germinate, heat-loving vegetable crops (cucumber, zucchini, pumpkin, tomato) are actively developing. The amount of BAP, degrees for a cucumber is 800-1000, active - not lower than +15 o С and not higher than + 42 ° С. Optimal for the growth and development of cucumber plants is the daytime temperature + 25 … + 30 ° С, and at night - + 15 … + 18 ° С. Different varieties have different optima, and this is where the selection of hybrids is important.
Optimum temperatures may not be the same for the growth of different organs of the same plant. Typically, the optimum temperature for growth of root systems is lower than for aboveground organs. For the growth of side shoots, the optimum temperature is lower compared to the growth of the main stem. For the growth of many plants, the changeable temperature during the day is favorable - increased during the day and lowered at night. This phenomenon is called thermoperiodism.
The phenomenon of thermoperiodism is also manifested in tomato culture. Lower night temperatures accelerate the growth of root systems and side shoots in plants. This must be taken into account when caring for a plant. If we talk about the forecast of climatic changes on Earth, then Japanese experts believe that the current appearance of four magnetic poles on the Sun will cause a temporary cessation of global warming. Similar phenomena on the Sun took place in the 17th-18th centuries. Then it coincided with a significant cooling on the Earth. But there is another point of view - about warming. One way or another, but the climate is an unpredictable value.
If we talk about cucumber hybrids, then in our climatic zone it is possible to plant both parthenocarpic or self-fertile F1 hybrids, and insect pollinated ones. Parthenocarpics have a higher yield, continuous fruiting, resistance to adverse weather conditions, and increased shade tolerance.
An important factor in the selection of a variety, a hybrid is taking into account its reaction to light. Of course, sometimes the producers of varieties are a little cunning, advertising them as shade-tolerant, but in fact they are light-loving plants. Let's take a look at the example of a tomato. The minimum illumination for its transition to flowering is 4-5 thousand lux (lux is the international unit of illumination), and for continuous development and fruiting - at least 10 thousand lux.
The so-called shade-tolerant varieties differ by about 3-5% from these values, although this is something. Seven phytochrome genes have been found in tomatoes, thanks to which the adaptation of the photosynthetic apparatus of plants to changing conditions and unfavorable environmental factors is ensured. And indeed, selection is being carried out in this direction, but the creation of shade-loving tomatoes is still far away.
Gardeners know from experience that a good harvest cannot be obtained from frail seedlings, no matter how wonderful the hybrid or variety is. In addition, all diseases come to visit a weakened plant. The variety shows its genetic qualities fully only under certain conditions, so its nature is arranged. If we grow healthy, strong seedlings, then they are much more likely to endure all the hardships of our climate.
And here light comes first. In tomato, cucumber, pepper, with an improvement in illumination, there is an acceleration of the beginning of flowering, the timing of the formation of the first brush and the number of leaves located before it decreases, the fruits are formed faster.
Read the next part. Harvest components: light - blue, red, violet … →
Vladimir Stepanov, Doctor of Biological Sciences