MOLECULAR CYTOGENETIC ANALYSIS OF RADIATION-INDUCED NEW TRANSLOCATION FROM A WHEAT LINE WITH A RYE DITELOSOME 2RL CARRYING THE HESSIAN FLY RESISTANCE GENE H21

The Hessian fly resistance gene H21 is present on the wheat-rye whole-arm translocation T2BS?2RL and was recently transferred to durum wheat. However, homozygous lines for this translocation have poor plant vigour; low seed set, and are almost completely sterile, making it impossible to use this germplasm directly in durum wheat improvement. The objective of this study was to reduce the rye segment in T2BS?2RL using irradiation, thereby making this gene available for wheat breeding. The plant material used in this study consisted of the H21 durum ditelos lines for chromosome 2RL. The mature pollen was collected from grown ditelos 2RL lines and was irradiated using the X-rays and then used to pollinate normal durum wheat plants. The Hessian fly resistant lines were analyzed using C-banding and GISH techniques. These techniques have revealed two newly recovered translocations. The resistant lines have retained distal part of rye chromosome 2R that carries the resistance gene H21 in the form T2AS.2AL-2RL translocation. Such recombination events are not of agronomic interest because they retain a nearly complete 2RL arm that has deleterious effects. Whereas, the susceptible lines had a small segment of proximal rye chromosome 2RL in the form of T2RL-2AL. This part of rye chromosome does not carry the resistance gene. This study has confirmed the utility of using the irradiation technique to reduce chromosome arms of the wild relatives such rye. Also, we have confirmed that irradiation is still random in breaking chromosomes and several translocations could be generated but the cytogenetic techniques such as C-banding and genomic in situ hybridization are very powerful techniques for identifying and selecting more interesting translocations.