Search

Polyploidy is an important factor in plant evolution that may trigger drastic genome reorganization and phenotypic differentiation. In the last decade, extensive studies have been carried to understand the consequences of allopolyploidization, where the effects of ploidy change may be confounded by interspecific hybridization. By contrast, less is known on autopolyploidization, which only involves doubling of homologous chromosomes. This study was undertaken to assess leaf anatomical modifications and gene expression changes occurring after doubling the somatic chromosome complement of diploid (2n = 2x = 24) potato species Solanum commersonii Dunal and S. bulbocastanum Dunal. Polyploidization did not induce qualitative changes in leaf structure and, for several leaf traits, anatomic modifications were stochastic. In addition, in both species a diploid superiority was generally observed, suggesting the occurrence of a high-ploidy syndrome. Expression change study was carried out on eight important cell cycle-regulatory genes in plant. It revealed a strong alteration of the expression patterns in the 4x genotypes with respect to the 2x parents. Changes often exceed the twofold, with no consistent trend towards up- or down regulation when comparing 2x vis-à-vis 4x. We discuss the possible relevance of epigenetic changes in controlling the expression of duplicated genes. [ABSTRACT FROM AUTHOR]

We report the accurate determination of the allelic configurations of a total of eight new citrus tetraploid hybrids by means of SSR analysis, coupled with capillary electrophoresis, and PCR based dosage effects. Tetraploid hybrids were spontaneously obtained from different interploid crosses (2x × 4x) between diploid ‘Femminello’ lemon and the allotetraploid somatic hybrid (2 n = 4x = 36) ‘Key’ lime + ‘Valencia’ orange, and between diploid ‘Wilking’ and ‘Fortune’ mandarins and an autotetraploid ‘Dancy’ mandarin (2 n = 4x = 36). To understand the opportunity to employ them in further backcross programs, the cytological mechanisms underlying their ploidy level were unambiguously determined using six SSR primers. PCR conditions were optimized and skewness in template/product ratios were verified. Tetraploid allelic configurations were determined from PCR based dosage effects using electropherogram peak heights to estimate the copy number per allele. In all the tetraploid hybrids we found out that diploginy (2 n eggs) has occurred, contributing the extra haploid genome in the tetraploids. According to the marker genotypes, it was further inferred that the 2 n eggs in ‘Femminello’ lemon resulted from first division restitution (FDR), while in ‘Wilking’ and ‘Fortune’ mandarins 2 n eggs occurred in second division restitution (SDR). These new genotypes, with their improved genetic female background, can be therefore considered very valuable in our citrus genetic improvement program as pollen donors in backcrosses suitable to eliminate negative traits. [ABSTRACT FROM AUTHOR]