We are starting our breeding program and we have a few questions. We are using clones which we bought or traded with other growers, along with a few varieties which we purchased as seed. The varieties from seed were all hybrids so we decided to self-cross them to get more uniform plants. We are in our third generation now. With each generation the plants look more alike, but the yield has gone down. Why is this happening?
The varieties from clones are only females. We were successful at producing stress-induced hermaphroditism using heat. We bring the temperature in the rooms up to about 100?F (38?C) and maintaining that temperature for a few days. So we have female pollen from the plants, but we were told that using induced males for breeding is not a good idea.
What do you think? If we can’t use the female pollen for breeding how should we go about it?
The original breeding stock was a hybrid and exhibited hybrid vigor. The plants which you are inbreeding through self-crosses are showing lower yield each generation because the genetic pool is becoming more homogeneous. This is to be expected. With rigorous selection your variety should be very stable in another two or three generations.
Using stress-induced pollen from female plants for breeding purposes is not a good idea. When inducing pollen from females, not every plant in the population produces it. The plants most likely to produce the pollen have more of a tendency to hermaphroditism than the plants that are not induced. By using these plants each generation, you are inadvertently selecting for hermaphroditism. The female-to-female cross is best used only for the last generation which are to be used only for bud production. These plants are much less likely to be naturally hermaphroditic than a group which was the result of several generations of female-to-female crosses.
Probably the best way to begin a breeding program with a clone is to cross the clone with a male from a similar variety to create a male population. Then backcross the male with the female clone you are interested in breeding. In five or six generations you will have a stable variety which is ready to breed.
Once the varieties are inbred or backcrossed so they are stable (that is, that plants from a batch of seeds will be quite similar), the plants are ready to be crossed. The homogeneous genetics of each line has resulted in uniformity at the cost of hybrid vigor. By crossing two inbred lines hybrid vigor will be restored and the f1 plants will be uniform because they are genetically similar.
This f1 line, which is to be used for production, would be a good candidate for a female-to-female cross. All the resulting plants will be uniform and female with just a slight tendency to hermaphroditism.
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