Potato germplasm enhancement with disomic tetraploid Solanum acaule. I. Efficiency of introgression

Abstract

The wild potato species Solanum acaule (acl) was used as a model of a disomic tetraploid Solanum species to develop systematic methods of germplasm enhancement for disomic tetraploid species. The objective was to develop a genetically efficient method to overcome the inherent technical problems encountered in the utilization of disomic tetraploid wild species. Accessions of acl were selected from CIP's wild germplasm collection and from the collection of University of Birmingham, with emphasis on genetic attributes such as PLRV resistance and (or) PSTV resistance. Four methods were tested: (i) triploids from crosses between 4x acl × 2x potato were selected for 2n gametes production and were crossed to tetraploids or to diploids with 2n egg production; (ii) axillary buds of triploid hybrids were treated with colchicine to double chromosome numbers to generate hexaploids; (iii) in vitro chromosome doubling to obtain hexaploids from triploid hybrids; and furthermore (iv) the selected acl clones were directly crossed to tetraploid potatoes followed by a combination of second compatible pollinations with IvP 35 and subsequent embryo rescue. The combination of second compatible pollination and embryo rescue was found to be the most genetically efficient method for the utilization of the valuable genetic attributes of acl.Key words: inter-EBN crosses, ploidy manipulation, polyploid, potato breeding, wild species