Cytological characterization of potato -Solanumetuberosumsomatic hybrids and their backcross progenies by genomic in situ hybridization

Abstract

Four somatic hybrids derived from a diploid wild species Solanum etuberosum and a diploid tuber-bearing Solanum clone 463-4, together with five BC1and three BC2plants, were analyzed by genomic in situ hybridization (GISH). None of the four somatic hybrids had the expected chromosome constitutions, i.e., 24 chromosomes from each fusion parent. Either one chromosome from S. etuberosum or one from the potato parent 463-4 was lost in the hybrids. Three BC1plants had exactly one set of S. etuberosum chromosomes. The other two BC1plants either had one extra or one fewer S. etuberosum chromosome, possibly because their somatic hybrid parents had an extra or had lost one S. etuberosum chromosome. The presence of one set, or close to one set, of S. etuberosum chromosomes in all BC1plants suggests a preferential pairing and segregation of the S. etuberosum chromosomes in the somatic hybrids. Two of the three BC2plants had 52 chromosomes, deviating significantly from the expected chromosome number of 48. These results suggest poor pairing between S. etuberosum and S. tuberosum chromosomes in the BC1plants. The present study demonstrates the importance of combining GISH and DNA marker analysis for a thorough characterization of potato germplasm containing chromosomes from different species.Key words: potato germplasm, Solanum etuberosum, molecular cytogenetics.