I think for two reasons or more

1- dependent of the source of variety from introduction, selection or hybrids.

2- The ideal or suitable spaces 300 meters for isolation of purity in sesame variety not 100 meters.

1. What is the portion of the contaminated seeds (ex. how many white seeds in the harvested black seeds)?

2. You might also already had seed contamination in the seed stock you used for propagation!?

3. Have the genes/alleles which control the 'color' been carefully studied? Can the 'different color' due to some kind of genetic interactions on the molecular level?

By the way, see the link below for the paper regarding genetic study of sesame color alleles (2014).

Paper title: Inheritance of seed coat color in sesame

http://www.scielo.br/scielo.php?pid=S0100-204X2014000400290&script=sci_arttext

They proposed:

"Sesame seed color is determined by the maternal genotype. Proposed names for the alleles participating in sesame seed coat color are: Sc1, for brown color; and Sc2, for white color; Sc1 is dominant over Sc2."

When dealing with just one clone or individual there is still a bit of lose genetics so that interlopers will creep in .  To produce hybrid lines for the breeding of annuals  two separate individuals are crossed and then the best of the desired characteristics are selected and crossed again . This process is repeated 6x , after which there should be no variation in the desired offspring ,  prior to 6x generations there is still some residual genetics that could show up.  I do not know about seeds but I do know that white in flowers is a recessive trait and while will quickly dissipate if out crossed in anyway .  Hence the rules of 6x generations.

That may be due to residual variation before released variety

Thank you very much for quick response of my question. I thick that one of the reason for such kind of variation may be residual genetics. But what about the transposeble element (Jumping gene theory)? Is there any possibility  of causing black seed in white seeded varieties and white seed in black seeded varieties due to the effects of transposeble element  (Jumping gene theory) as occurs in Maize. Anybody come across such references?

Hi Bachubhai,

For your last post:

1. Transposon elements (TEs) can be one possibility, but you need to have  evidence. To verify, the gene(s) or alleles controlling this trait need to be cloned and sequences are known. Then you can sequence the alleles to see whether there is an insert or 'footprint' of the TE in the specific alleles. But, according to the 2014 paper I attached for you earlier, they JUST proposed the 'names' of the alleles. So, I bet that the alleles most likely have not been cloned and sequenced yet. It will be a long way to go.

2. Through your request, I attached a page of document and a picture describing 'Color change due to TE insertion', in animals and plants, for your reference. The info is taken from 2007 Nature Reviews Genetics  [ http://www.nature.com/nrg/journal/v8/n4/fig_tab/nrg2072_F2.html ].

Sesame has natural outcrossing, so the isolation distance recommended in one location may not be ideal for another. Insect activity and wind and its directions need to be taken into consideration. I have my doubts if this is due to transposons, but can not be excluded without genetic studies of the progenies from black seeds.

sesame is one of the crops that is highly selfpollinated, however sometime due to insects movement, outcrossing may occur, which during seed multiplication of the foundation seed  might lead to segregation for the genes that controlling seed color in sesame. this of course needs further genetic study, considering isolation distance

Thank you very much for sparing your valuable time to updating my knowledge. Thanks again.

1.  @ Bachubhai, according to previous posts from other members, to understand the pollination type of sesame is also important in answering your question.

2. Regarding to the pollination style ('outcrossing' or 'self-pollinated') of sesame :

According to the paper (2014) attached below, the authors think "....it is still lack of info on the pollination of sesame in the literature and its contradictions...... They have therefore conducted a research on this topic and get some results. Please see the yellow-highlighted paragraphs (especially the 'Conclusions') in the paper.

Thanks for taking pain to provide me valuable information