Abstract: Background: Polyploidy (whole-genome duplication) is an important speciation mechanism, particularly in plants. Gene loss, silencing, and the formation of novel gene complexes are some of the consequences that the new polyploid genome may experience. Despite the recurrent nature of polyploidy, little is known about the genomic outcome of independent polyploidization events. Here, we analyze the fate of genes duplicated by polyploidy (homoeologs) in multiple individuals from ten natural populations of Tragopogon miscellus (Asteraceae), all of which formed independently from T. dubius and T. pratensis less than 80 years ago. Results: Of the 13 loci analyzed in 84 T. miscellus individuals, 11 showed loss of at least one parental homoeolog in the young allopolyploids. Two loci were retained in duplicate for all polyploid individuals included in this study. Nearly half (48%) of the individuals examined lost a homoeolog of at least one locus, with several individuals showing loss at more than one locus. Patterns of loss were stochastic among individuals from the independently formed populations, except that the T. dubius copy was lost twice as often as T. pratensis. Conclusion: This study represents the most extensive survey of the fate of genes duplicated by allopolyploidy in individuals from natural populations. Our results indicate that the road to genome downsizing and ultimate genetic diploidization may occur quickly through homoeolog loss, but with some genes consistently maintained as duplicates. Other genes consistently show evidence of homoeolog loss, suggesting repetitive aspects to polyploid genome evolution.

Abstract: One partial asynaptic mutant of Vicia faba (2n=12) was isolated from M2 population of 0.2% EMS (Ethyl Methane Sulphonate) treated seeds. The mutant was designated as ‘medium strong asynaptic mutant’. At diakinesis/metaphase I of meiosis number of univalents ranged from 2–8 in 90% of PMCs in M2 and 2–4 in 44% of PMCs in M3. There was a significant decrease in the number of chiasmata in this plant as compared to the control. The metacentric chromosome pair did not show univalence. The pollen fertility was also reduced by 35%. The inheritance of this asynaptic mutant was probably of monogenic recessive type.

Abstract: In the present study, 30 seeds of Vicia faba (2n=12) treated with 0.005% colchicine for 8 h produced 15 polyploids. The success of induction of polyploidy by this method was 50%, which is very high as compared to any other methods used so far in this species. Presoaking the seeds in distilled water for ∼20 h proved more effective in inducing the polyploidy. Typical polyploid characters like gigantism, bigger leaves, flowers and pods etc. were exhibited by the induced colchitetraploids, however, they had reduced pollen fertility and number of seeds/pod and plant as compared to diploids. Polyploidy was confirmed by chromosome counts (2n=4x=24) at meiosis as well as at root tip mitosis. The method is easy and reliable for successful induction of polyploidy with colchicine in this species. We also recommend this method for induction of polyploids in other leguminous crops.

Abstract: Seven translocation heterozygotes (5 with gamma rays and 2 with EMS treatment ) and 2 paracentric inversion heterozygotes (both in gamma ray treated materials) were induced in broad bean (Vicia faba). Three of the translocation gheterozygotes involved the metacentric chromosome pair where as the remaining 4 had translocations in the acrocentric chromosomes pairs. The induced translocations showed a ring or chain of 4 chromosomes in most of the PMCs at diakinesis/metaphase I. The paracentric inversions were detected as a distinct bridge and fragment or loop-fragment observed at meiotic anaphase I/II. All the induced mutants showed reduced vigour, less number of basal branches, delayed flowering, low flower number, low pollen fertility, reduced number of pods and low seed set as compared to those in control plants.

Abstract: