Sunflower cross-pollination isolation distance ?

[nicollas]

Hi,

i would like to maintain several sunflower populations on a small space. I'm not in a quest of a big purity, but i'll cant spot population-hybrids if some cross pollination occurs. Have you an idea of the minimal distance to maintain to limit the cross pollination to maybe 5% ? Thanks

Maybe i'll make relay plating but i dont know yet the number of day until flowring and i expect variability among each population so i dont know if it is relevant.

[Joseph Lofthouse]

I get around a 5% cross pollination rate on squash separated by 100 feet. I got about a 5% viable seed rate on a sunroot clone (self incompatible) that was growing 70 feet away from a pollen source.

I expect single sunflower plants to flower over an extended period of time, and a genetically diverse population would have an even longer flowering time, so I don't know how possible it would be to separate the populations by planting dates. I've been struggling though with sunroots, because I want to make a hybrid, but flowering times between my two strains do not overlap most years.

[nicollas]

Thanks for th inputs Joseph. 70 ft is already a great distance for my land, i'll have to figure how to proceed if i want 2 or 3 populations