Meiotic behavior of pollen mother cells in relation to ploidy level of somatic hybrids between Solanum tuberosum and S. chacoense

Abstract

Potato somatic hybrids obtained by protoplast fusion between Solanum tuberosum (4x) and Solanum chacoense (2x) were investigated for genome stability and meiotic behavior associated with the pollen viability in order to elucidate the mechanism influencing the fertility of the somatic hybrids. The ploidy level detections conducted in 2004 and 2007 demonstrated that 68 out of 108 somatic hybrids had their ploidy level changed to be uniform and euploidy after successive in vitro subcultures, which mainly occurred in octaploids, aneuploids, and mixoploids, while 74% hexaploids were still stable in their genome dosage in 2007. Different types of abnormal meiotic behavior were observed during the development of pollen mother cells (PMCs) including the formation of univalents, multivalents, laggard chromosomes, and chromosomal bridges, as well as triads and polyads. A higher proportion of abnormal meiosis seemed to be accompanied with a genome dosage higher than the hexaploids expected in this study. A significant positive correlation between defective PMCs and the number of small pollen grains and negative correlation between number of small pollen grains and pollen viability strongly suggested that abnormal meiosis could be a causal factor influencing the fertility of the somatic hybrids. The hexaploids with stable genome dosage and a certain level of fertility will have great potential in a potato breeding program.

Backcrossing to increase meiotic stability in triticale

“…The cross of F 2 with 'Embrapa 53' (resulting in BC 1a ) also presented 9% more normal cells than 'Embrapa 53'. Similar results to those of the present study have been described regarding backcrosses in Brassica sp (Hauser et al, 1998), as well as in Solanum tuberosum and Solanum chacoense (Guo et al, 2010). Considered together, these results indicate that genomic stability in triticale may be improved by performing crosses between more stable lines and their respective parents.…”

“…Several studies have reported improvements in the number of normal cells during meiosis when segregating genotypes are crossed with their parents (Hauser et al, 1998;Guo et al, 2010). However, these studies have been conducted and confirmed in relatively few species.…”

Development of somatic hybrids Solanum × michoacanum Bitter. (Rydb.) (+) S. tuberosum L. and autofused 4x S. × michoacanum plants as potential sources of late blight resistance for potato breeding

“…It is responsible for the late blight disease, which results in 10–15 % reduction of the global production of potato tubers (Kamoun and Smart 2005; Park et al 2009). Identification of new sources of resistance to P. infestans and introgression of novel resistance genes from wild potato species into the tetraploid potato genepool is a way to achieve the progress in breeding of the cultivated potatoes resistant to late blight (Zimnoch-Guzowska et al 2003; Guo et al 2010). Due to differences in the ploidy level or in the Endosperm Balance Number (EBN) many wild potato species cannot be used as late blight resistance donors in crosses with tbr (Borgato et al 2007; Tiwari et al 2010).…”

Protoplast fusion in the genus Gentiana: genomic composition and genetic stability of somatic hybrids between Gentiana kurroo Royle and G. cruciata L.

“…Some hybrid lines of P. malacoides (+) P. obconica showed a decrease in DNA content during the plant regeneration process (Mizuhiro et al 2001). More recently, Guo et al (2010) reported that somatic hybrids between S. tuberosum and S. chacoense underwent gradual DNA elimination during 3 years of in vitro culture. This phenomenon was most evident when hybrids had an initial DNA content greater than the sum of parental species DNA, or they were aneuploids and mixoploids.…”

“…However, regeneration of plants from fused protoplasts is often accompanied by polyploidization and/or the elimination of genome parts of either one or both fusion parents (Babiychuk et al 1992;Oberwalder et al 1998;Mizuhiro et al 2001;Guo et al 2010). Thus, detailed investigation is needed, not only to confirm the hybrid status of regenerants, but also to characterize precisely their genome size and composition, which is essential for their further efficient exploitation (SmydaDajmund et al 2016).…”