Epigenetic consequences of interploidal hybridisation in synthetic and natural interspecific potato hybrids.

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (that is genetic, epigenetic and phenotypic novelties). Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and single sequence repeart (SSR)), epigenetic (MSAP), and cytological comparisons in: (1) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum × rechei (2n = 2×, 3×) and its parental species, the triploid cytotype of Solanum microdontum (2n = 2×, 3×) and Solanum kurtzianum (2n = 2×); and (2) newly synthesised intraploidal (2× × 2×) and interploidal (3× × 2×) S. microdontum × S. kurtzianum hybrids. Aneuploidy was detected in S. × rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S. × rechei compared to its parental species in nature. These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation.

Somaclonal variation in Asparagus officinalis plants regenerated by organogenesis from long-term callus cultures

Somaclonal variation in plants regenerated by organogenesis from long-term cultured calluses of two diploid staminate genotypes of Asparagus officinalis cv. Argenteuil was characterized by plant phenotype, ploidy, meiotic behavior, pollen viability, fruit and seed set, and AFLP profiles. Phenotypic deviations from the donors were detected in foliage color, flower size, and cladode and flower morphology. Ploidy changes were observed in 37.8 percent of the 37 regenerants studied. Meiotic alterations in 12 out of 21 regenerants included laggards, dicentric bridges, micronuclei, restitution nuclei and polyads. Of the 408 AFLP markers screened in 43 regenerants and the donors, 2.94 percent showed polymorphism. High pollen viability was observed in the 22 regenerants analyzed. All crosses between one pistillate plant and 35 regenerants, as well as the controls, produced fruits and seeds; however, no plump seeds resulted in 35.3 percent of the crosses with regenerants, and no seeds germinated in 12.5 percent of those with apparently normal seeds. Fruit and seed set was similar in crosses with diploid regenerants with normal meiosis and the controls but was lower in crosses with diploid and polyploid regenerants with abnormal meiosis. Our results show that the regenerated plants exhibited conspicuous somaclonal variation that could be eventually exploited for in vitro selection systems.

Somatic embryogenesis in Asparagus officinalis L. cv. Argenteuil: interactions between genotype, explant type and growth regulators on callus induction, growth and embryogenic differentiation

Callus induction, growth and embryogenic differentiation were studied in two selected genotypes of Asparagus officinalis L. cv. Argenteuil, to develop a protocol for somatic embryogenesis. Two experiments were carried out. In the first, four explant types (spear sections and lateral buds, both of in vivo and in vitro origin), and three levels of 2,4-D (1.5, 5 and 10 mg.l-1) and two of KIN (0 and 1 mg.l-1) added to MS basal medium, were tested during the three initial culture stages (90 d period). All factors were included in one factorial design to statistically analyze interaction effects. Interactions between genotype, explant type and time of culture initiation were significant for callus induction and growth during the two initial culture stages. The addition of kinetin enhanced callus induction and growth, and high levels of 2,4-D depressed callus growth. The average embryogenic differentiation was < 2 overall (11 with the best factor combination). In the second experiment, another explant type (bud clusters) was tested; the average embryogenic differentiation was 1.9 (best combination: 5.6). For the two genotypes studied, the best factor combinations were the culture of in vivo lateral buds or bud clusters on MS basal medium with 1.5 mg.l-1 2,4-D and 1 mg.l-1 KIN.(AU)

Somatic embryogenesis in Asparagus officinalis L. cv. Argenteuil: interactions between genotype, explant type and growth regulators on callus induction, growth and embryogenic differentiation

Callus induction, growth and embryogenic differentiation were studied in two selected genotypes of Asparagus officinalis L. cv. Argenteuil, to develop a protocol for somatic embryogenesis. Two experiments were carried out. In the first, four explant types (spear sections and lateral buds, both of in vivo and in vitro origin), and three levels of 2,4-D (1.5, 5 and 10 mg.l-1) and two of KIN (0 and 1 mg.l-1) added to MS basal medium, were tested during the three initial culture stages (90 d period). All factors were included in one factorial design to statistically analyze interaction effects. Interactions between genotype, explant type and time of culture initiation were significant for callus induction and growth during the two initial culture stages. The addition of kinetin enhanced callus induction and growth, and high levels of 2,4-D depressed callus growth. The average embryogenic differentiation was < 2 overall (11 with the best factor combination). In the second experiment, another explant type (bud clusters) was tested; the average embryogenic differentiation was 1.9 (best combination: 5.6). For the two genotypes studied, the best factor combinations were the culture of in vivo lateral buds or bud clusters on MS basal medium with 1.5 mg.l-1 2,4-D and 1 mg.l-1 KIN.