Recombination behaviour and gene transfer in Petunia hybrida after pollen irradiation

Summary

The genes An2, Rt and An1 are located in chromosome VI and closely linked. Pollination of the triple recessive line W127 (an2an2rtrtan1) with irradiated pollen of the triple dominant line M1 (An2An2RtRtAn1An1) led to the recovery of at least 3.3% induced an2 recessives. Karyotype analysis and genetic data showed that these mutants all contained a deletion on the short arm of chromosome VI, ranging from “non-detectable” (a non-transmissable mutant, showing no visible deletion) to the complete short arm. It is concluded that An2 is located distally in the short arm, Rt and An1 in the long arm of chromosome VI. Deleted chromosomes are not transmitted to the next generation, neither through the male nor through the female; transmission of the dominant markers in the long arm of chromosome VI is possible after completion of the chromosome by crossing-over. There is a relationship between the length of the deletion in the short arm and the recombination frequency between the markers (Rt and An1) in the long arm: recombination increases with increasing length of the deletion. After completion of the chromosme by crossing-over, the normal recombination frequency is restored.