Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 131

The genetic consequences of inbreeding were alluded to in Section 3.8. The tendency toward homozygosity with inbreeding provides an opportunity for recessive alleles to be homozygous and hence expressed. Whereas inbreeding generally has little or no adverse effect in inbred species, crossbred species suffer adverse consequences when the recessive alleles are less favorable than the dominant alleles. Called inbreeding depression, it is manifested as a reduction in performance, because of the expression of less fit or deleterious alleles. The severity of inbreeding depression varies among species, being extreme in species such as alfalfa in which inbreeding produces homozygous plants that fail to survive. Further, the effect of inbreeding is most significant in the first five to eight generations, and negligible after the eighth generation in many cases.