Crosstype

Crosstype is a label used in genetics and plant and animal breeding to describe the design of a genetic cross. In experimental records, publications, and breeding databases, crosstype identifies how the parental lines were chosen and how the offspring were produced. The term is often used interchangeably with "cross type" or "type of cross."

Common cross types include self-cross (selfing), where an individual is fertilized by its own pollen or gametes; backcross (BC), in which the offspring are crossed back to one of the parental lines to introduce or fix specific alleles; reciprocal cross, where the same two parental genotypes are used in two crosses with swapped sexes; diallel cross, where all possible crosses among a set of lines are performed to evaluate general and specific combining ability; and test cross, in which an unknown genotype is crossed with a homozygous recessive tester to reveal recessive alleles.

Usage and interpretation: The crosstype informs expectations for heterozygosity and segregation patterns and influences the design of experiments and subsequent data analysis, such as mapping or quantitative trait locus studies.

Notation and standards: Because the term is not universally standardized, crosstype codes vary by field and software. Typical records may encode self-cross as SC or S, backcross as BC, reciprocal cross as RC, and diallel as DI or DIAL.

Limitations: In some contexts, "crosstype" may be insufficient to describe complex crossing schemes or poly-cross designs; researchers should provide a complete description of parental genotypes and crossing schedule.