Theory mentions that cross-breeding will introduce new genes in a population, for which it would be better prepared to face pathogens. However, in my bacterial challenge the improved families had a 70% mortality while the pure lines had only 20%. Does anyone know what this can be?
dear José Hernández
The cross-breeding would be better prepared to face pathogens if choice the best the parent of the cross with maximum Genetic distance and selected rightly in segregating population.
Yes I agree with Muthana. Your selection gives you more randomness within the genome which might be good to fight against other pathogens.
Crossbreeding combines multiple breeds in very tightly controlled ratios. From your description ("cross-breeding will introduce new genes in a population ") I assume that your pure breed is resistant whilst the second breed is not. The offspring will be always 50/50 mix of the two parent breeds, so if only one has the desired caracter, the result is twice diluted. Or maybe your pure genetic line is 80% resistant due to an additional immunomodulator favoring that resistance, which was not transmitted or significantly diminished via cross-breeding.
The issue is that the individual evaluation of the three parental lines (which are three crayfish populations with different origin), all three showed a greater survival than all the crosses generated. There isnt a mixture of the offspring.
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