You could potentially create tetraploid marigolds, but they may not have the nematicidal activity that you are hoping for since you would have no idea what doubling the genome would do to the progeny plants. A better approach would be to identify the genes involved in nematode defense and duplicate and/or over-express the genes in the roots and/or whole plant. You would have to take a cisgenic approach with promoters specific for the roots (to express in the roots) or use the 35s promoter to over-express in the entire plant.

Thank you very much for your answer A G , i am private researcher and work alone to resolve my current problems (and possibly problems in my future commercial bulb plantation) with pests and disease by "WHAT I HAVE IN MY HAND" i have searched for nematicides and found nothing due to trade embargo only some soil fumigants that is useless for me because they are highly toxic .I can try to product tetraploid plants with Oryzalin with my limit equipment's but production of transgenic plants is impossible for me .I talk with our agents of Agriculture department in our province but they have no experience with nematodes.I read some articles from Hawaii , that they use marigolds to attack nematodes and i decide to work on marigolds that are easy to grow and breed for me .

I totally agree with Dr. Laney. But as you do not have any facility to develop transgenic plants, the process of creating tetraploidy or mutants and testing each new tetraploid for their nematacidal activity is very cumbursome. Apart, as mentioned by Dr. AG, you would not know what the genomic outcome may be. Directed cisgenic approch is always helpful in such studies. However, give the tetraploid idea a try, can't say, you may get a mutant that may have high nematacidal activity. All the best.

cheers

Vivek Kempraj

If your goal is to try and control nematodes and other soil-borne pathogens, you may want to investigate using mustard as a cover crop and/or soil solarization:

http://www.plantmanagementnetwork.org/pub/cm/research/2003/mustard/

http://www.ext.colostate.edu/pubs/crops/00505.html

Mustard cover crops seem to be a likely alternative to fumigation, they make their own, and it adds nutrients back into the soil. As is, mustard has been shown to be effective so you wouldn't have to mess around with the marigolds which are generally less effective. Soil solarization can kill off beneficial microorganisms, but it also kills off pathogens as well. A big issue is that it is labor intensive to place the plastic and then collect it after solarization.

I have read some articles about mustard's too , My goal is to plant marigolds close to lily bulbs to see if marigolds can help to protect bulbs and their roots , mustard's are effective too but they work well if i use them as green manure before planting bulbs but bulbs are planted , for future trials mustard's are good idea to enrich the soil and reduce nematodes but for now I think that living roots of marigolds are only way .

The population dynamics of PPNs need to be understood before going for specific biocontrol and management practices. Marigold may be effective for a particular set of nematodes, However the kind of species will determine the suitability of your module as the allelopathic interactions at molecular level shall be dependent on what molecules are released by plants and their effectiveness against which nematode species. Even cis or trans genic approach with suitable promoters shall be effective only with known chemistry between the allelochemicals and nematodes.

Hi

Induction of nematicidal activity by doubling the number of chromosomes just like that does not seem to be a very promising alternative. In that case screening of induced mutants might do, but that is a long shoot. It might be better to look for resistance on the primary, secondary and/or tertiary relatives (gene pools) of marygold. Once you find a resistant individual it would be easier to transfer genomes or chromosomes carrying the trait to select for stable lines with resistance to nematodes. That would be done just by traditional crossing. In such case you will still need recombinant technology to identify and characterize the resistant individuals.

Hi

Marigolds have nematicidal activity in their root so there is no need to induce nematicidal activity i just want to increase it and breed new varieties with ability to attack more nematode species .different marigold species have ability to attack different kind of nematode species but with a hybrid between these species or with stronger nematicidal activity we may can breed new marigolds with more nematode control .

I've done a bit more research on the matter and I don't think that you are going to see the results that you are hoping for. Many tetraploid marigolds already exist with the first ones being created in the 1930s. I have been looking online and I have found no reports that tetraploid marigolds have more nematode resistance than the diploid ones; and even then not all types of nematodes are controlled. Some species of nematodes actually increase with marigolds (like the sting and stubby-root nematodes). And studies intercropping susceptible plants with marigolds really haven't shown any successful results, but there are several with negative or ambiguous results. You can try obtaining some seeds for tetraploid marigolds and compare them to diploid if you want to go that route. I still think your best bet is either a transgenic or a cisgenic plant if you are sticking with marigolds as a control method. But like I stated above using mustard as a green manure would be the best option as it is broad spectrum.

A link on nematode control with marigolds:

http://edis.ifas.ufl.edu/ng045

Here is a link on the history of tetraploid marigolds:

http://www.mpiwg-berlin.mpg.de/Preprints/P393.PDF#page=261

Thank you A.G for your valued information . i find some good mustard variety in USA but sellers don't accept to send seeds to Iran , i send email and message to my friend in USA to see if they can receive seeds and resend me . Mighty Mustard "Kodiak" impress me with its high biomass and highest bio fumigants .I want to order about 200 seeds to grow and test them here .I don't find any research or experience about using mustards as bio fumigants in Iran and i hope that i can be first .

Hi, Mohamed; If you can easily double the chromosome number from your marigolds (you may use colchicine), just try it and see what happens... See if you can get different marigold accesses in your trials. It will not be that expensive doing tests like that. Of course, as indicated by our colleagues above, there is no guarantee you will get what you are expecting... Good luck.