I irradiated the seeds of a summer onion variety, BARI Piaz-2 with 75 an 100 Gy doses of gamma rays, raised seedlings along with an unirradiated control of the parent. After 55 days, I planted the seedlings in the field and found in M1 generation all the irradiated plants in both the doses flowered and produced seeds but the plants from un-irradiated control parent did not. I grow the seeds obtained from the he M1 plants and seedlings were transplanted on 15th December at an age of 50-55 days in the next year .Again, I found most of the M2 populations flowered and produced seed unlike the parent and till M10 generation similar result. In case of the parent, some ( very negligible) plants flower and also produce seed. But when the temperature rises in the later part of January and February the parent can not flower at all but the mutants can. In Bangladesh, the lowest temperature prevails in mostly December and January although winter season starts from November and ends in January.
I studied the chromosomes also of the onion mutants and found that the length of the individual chromosome and total chromosomes increased
considerably compare to the parent. The structure of the chromosomes based on centromeric positions also changed in the mutants compare to parent. But the chromosome structure studies did not give the same result in both the studies.
I would suggest for you to cross each of the original M0 or M1 putative mutant lines (or any later generation putative mutants) to the wild type (original mother plant line).
1) Once you get the progenies (seeds), plant each of them and generate vegetative planting materials (grow the seeds, generate bulbs from each seeds but prevent them from flowering). You want to harvest at least two bulbs per seed (the more, the better).
2) plant one of the bulbs from point 1 (save the clonal counterpart), let them produce seeds (keep seeds separately for each pedigree), and use the seed family for progeny test (plant 20-25 progeny seeds/family)
3) evaluate the segregation for the annual flowering ability among plant growing from 20-25 seeds/plant. If the progeny test resulted in either 💯% flowering or 0% flowering, you may disregard the related clone bulb in step 1. But if the progeny test yield segregated phenotypes, i.e. some plants in progeny test flower and the others are not. Go back to the related clone bulb and go to the next step.
4) grow the selected bulbs, identified based on progeny analysis in step 3 to maturity, let them flower and backcross the plants to the wild type. Safe the back cross progenies separately and use them for segregation analysis.
5) plant the backcross seeds to maturity and evaluate the backcross progenies flowering abilities. If the phenotype is controlled genetically, by mutated single gene in the original mutant lines then you will see a 1:1 segragation between flowering vs. non-flowering progenies (you may possibly find different phenotype ratio, depending on the genetic control of the annual flowering phenotype. If you do not see specific segregation ratios, then possibly the phenotype is not genetically controlled. Do plan enough seed progenies in step 5 to capture the segregation ratios with 5% level of alpha. Please evaluate the ratio using the expected model and test the model acceptance by Chi-Square distribution test.
Those steps are just scenario you can follow, off courae there are many other waya to answer your same queations. Good luck.
Dear S. Sudarsono
Thank you very much for your detailed activities to be followed to prove whether the mutants are really mutation derived or just admixture.
Regards,
Azad
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