ENDOSPERM BALANCE NUMBER MANIPULATION FOR DIRECT IN-VIVO GERMPLASM INTROGRESSION TO POTATO FROM A SEXUALLY ISOLATED RELATIVE (SOLANUM-COMMERSONII DUN.)

Diploid (2n = 2x = 24) Solanum species with endosperm balance number ( EBN) = 1 are sexually isolated from diploid 2EBN species and both tetr aploid (2n = 4x = 48, 4EBN) and haploid (2n = 2x = 24, 2EBN) S. tubero sum Group Tuberosum, To sexually overcome these crossing barriers in t he diploid species S. commersonii (1EBN), the manipulation of the EBN was accomplished by scaling up and down ploidy levels, Triploid Fl hyb rids between an in vitro-doubled clone of S. commersonii (2n = 4x = 48 , 2EBN) and diploid 2EBN clones were successfully used in 3x x 4x cros ses with S. tuberosum Group Tuberosum, resulting in pentaploid/near pe ntaploid BC1 progenies, This provided evidence of 2n (3x) egg formatio n in the triploid female parents, Two selected BC1 pentaploid hybrids were successfully backcrossed both as male and as female parents with S. tuberosum Group Tuberosum, The somatic chromosome number varied gre atly among the resulting BC2 progenies, which included hyperaneuploids , but also a number (4.8%) of 48-chromosome plants, The introgression of S. commersonii genomes was confirmed by the presence of S, commerso nii-specific randomly amplified polymorphic DNA markers in the BC2 pop ulation analyzed, The results clearly demonstrate the feasibility of g ermplasm introgression from sexually isolated diploid 1EBN species int o the 4x (4EBN) gene pool of the cultivated potato using sexual hybrid ization, Based on the amount and type of genetic variation generated, cumbersomeness, general applicability, costs, and other factors, it wo uld be interesting to compare the approach reported here with other in vitro or in vivo, direct or indirect, approaches previously reported.