Karyotype analyses and studies on the nuclear DNA content in 30 genotypes of potato (Solanum tuberosum) L.

Abstract

The cytophotometric estimation of 4C DNA content, and karyotypic and somatic chromosome number analyses were carried out in 30 genotypes comprising seven cultivars and 23 advanced breeding lines of Solanum tuberosum. Detailed karyotype analysis revealed genotype specific chromosomal characteristics and structural alterations in chromosomes of the genome, with a rare phenomenon of aneusomatic (2n = 4x + 2 = 50) condition in cv.K. Chandramukhi. The origin of this variation could be attributed to mitotic non-disjunction in the shoots giving rise to aneusomatic roots. Highly significant variations in the genome length, volume and total form percentage were noted at the cultivar level. The total chromosome length varied from 84.56 microm in cv.K. Pukhraj to 127.62 microm in MS/89-60, with an average value of 100.94 microm +/- 1.82. Total chromosome volume varied from 57.22 microm3 in MS/92-1090 to 132.64 microm3 in JW-160. Significant variations in the 4C DNA content (7.28-15.83 pg) were recorded at the cultivar level, with an exceptionally high DNA content (22.24 pg) in cv.K. Chandramukhi. This could be due to the aneusomatic condition of this genotype. Correlation studies revealed interdependence between the chromosomal and nuclear parameters of the genotypes. Structural alterations in the chromosomes, as well as loss or addition of highly repetitive sequences in the genome, caused variations in DNA content at the cultivar level. Variations in genomic structure and nuclear DNA content of the 48-chromosome genotypes suggest a genetic drift during microevolution, leading to the development of new cultivars.

Karyotypic Evolution and Molecular Cytogenetic Analysis of Solanum pinnatisectum, a New Source of Resistance to Late Blight and Colorado Potato Beetle in Potato

“…Using pachytene analysis of haploids, Yeh and Peloquin (1965) found no gross structural differences between haploids of the groups Tuberosum and Andigena. However, recent karyotypic analyses and studies on the nuclear DNA content showed that highly significant variations were observed in the genome length, volume and total form percentage at the cultivar level in 30 genotypes of cultivated potato (Mohanty et al 2004). In the present study, karyotypic analysis of diploid Mexican S. pinnatisectum and tetraploid S. tuberosum for the number of metacentric and telocentric chromosomes demonstrated that, although most of the chromosomes were morphologically similar, there were large structural differences between these 2 species.…”

“…Identification of the potato chromosomes based on their length, centromeric position, arm ratio, and morphological characteristics is possible at mitosis using the present technique. There has been no detailed karyotype studies published for diploid Mexican species S. pinnatisectum, although some preliminary karyotype of dihaploid and tetraploid cultivated potato had been analysed (Yeh and Peloquin 1965, Visser et al 1988, Mohanty et al 2004. Using pachytene analysis of haploids, Yeh and Peloquin (1965) found no gross structural differences between haploids of the groups Tuberosum and Andigena.…”

“…This indicated that structural rearrangements, such as deletions and translocations had occurred during the evolution of potato from diploid to tetraploid species. The reduction of the number of metacentric and constriction-like chromosomes might have occurred during the course of the evolution through mutations, and structural and physiological changes (Schultz-Schaeffer 1960, Mohanty et al 2004). The longest chromosome 1 in both diploid and tetraploid species had constriction-like regions on the long arms.…”

“…However, chromosome identification is more of a challenge in many plant species with small chromosomes, such as potato. Although some karyotype descriptions have been reported in potato (Yeh and Peloquin 1965, Visser et al 1988, Mohanty et al 2004, cytogenetical information still lack for both diploid and tetraploid in the genus Solanum, especially for the diploid Mexican wild species (Wilkinson 1994). This is mainly due to problems associated with difficulties in the preparation of good chromosome spreads, small chromosome size with very similar morphology, and the low natural frequency of synchronously dividing cells in root-tip meristems (Hawkes 1979).…”

Determinación de la ploidía en accesiones de papas nativas (Solanum tuberosum grupo Andigenum) procedentes del Banco de Germoplasma vegetal de CORPOICA

“…Mohanty et al [15] identificaron alteraciones estructurales en cromosomas produciendo un fenómeno raro de aneugénesis (2n = 4xC2 = 50). Esta variación fue atribuida a la no disyunción mitótica de los tallos, dando origen a raíces aneusomáticas, sin embargo, se pudo confirmar que estas accesiones contaban con una dotación cromosómica de 48 y 24 cromosomas perteneciendo al grupo andigenum (Tabla II).…”