I am aware the said plant is a x species Hybrid. My Jusbertii has just produced some small flower buds and I have a few thoughts.

Due to it being a Hybrid I need to cross this plant with an echinopsis to produce seed. I have several Trichocereus sp that will flower pretty soon and I wonder if I can use one of these to do it. Given Trichos are clasified as echinopsis now there should be no poblem....right ?? I'm not very exprienced when it comes to this area and any help appreciated.

Harrisia and Tricos are related?

Well...I guess in a round about way. They will be closer related if this works

The idea behind it is this. H.Jusbertii is an intergeneric hybrid and was prouced by crossing Harrissia Sp with a Echinopsis Sp (Eyriesii). Now due to the Harissia being the mother when Jusbertii flowers you need an echinopsis father to produce seed .

I'm just wondering, if Trochos are in essence classified an echinopsis then in theory it should work ?

im guessing it will work seeing as a Trichocereus is essentially just a tall Echinopsis, which is why they are in the same genus now. in any case it is worth a shot!
try also crossing it with 'real' echinopsis like E. oxygona and eyresii too if you have the chance.

Well only one way to find out. Lewis I would try a cross with another echinopsis but I don't have any. Mine are all Trichos. If anyone has an echinopsis that will flower in the next say 3 weeks send me a PM and we can split the resulting seed

all you can do it is try i have only tried selfing them and that has gotten me nowhere lol. i would love to see how this works