Issai variants


#1

Hello all,

Some of you may know me from the old Gardenweb site as Kiwinut. I stumbled across the Growing Fruit site a few months ago (kudos to Scott!), and have read a lot, but I’m just now getting around to posting. I used to do a lot of kiwifruit growing and breeding, but now only dabbling a bit with grapes, kiwi and passionfruit.

I wanted to share some relatively new info based on recent research regarding Actinidia collections in the US and more specifically relating to the cultivar(s) ‘Issai’. The reason I say cultivars, is that there are more than one genotype sold as ‘Issai’ in the US. ‘Issai’ is a name used in Japan for any precocious, parthenocarpic Actinidia arguta selection, as it translates to “year one” or “first year”. For many years, what we called ‘Issai’ was thought to have a possible hybrid origin from a cross of A. rufa x A. arguta and is hexaploid. We now know that there are populations of wild hexaploid A. arguta in the snowy mountain areas of north central Japan, as well as tetraploid A. arguta. The ‘Issai’ selections very likely originated in these areas.

In 2017, researchers at the Univ. of New Hampshire developed genetic markers for hardy kiwi species and analyzed the germplasm available at the USDA repositories, university collections and a number of nurseries. The markers can distinguish between A. arguta, A. kolomikta and A. polygama. They found that the majority of A. arguta cultivars in the US are duplicates of the same genotypes that have been given new names by nurseries, or were mixed up over the years. The genetic analyses could also be used to determine the ploidy of all the cultivars. The work can be read here, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170580.

One of the more interesting results involved ‘Issai’. It was determined that there are two different genotypes sold in the US as ‘Issai’. One is referred to as the “long-fruit variant” and the other as the “small fruit” or “round fruit” variant. It turns out that the small/round fruit variant is hexaploid, but the long-fruit variant (the more common one?) is actually tetraploid. Both seem to be very closely related, although I don’t know how close that really is. The other interesting discovery is the male ‘Flowercloud’, was also found to be very closely related to the 'Issai’s and most closely related to the tetraploid variant. They also found that ‘Flowercloud’ is just a precocious tetraploid A. arguta, and not a hybrid with A. kolomikta as claimed by many nurseries.

The main reason I am posting this is to ask everyone growing ‘Issai’, which version do you have and where did you get it? Both versions are present in the repositories, but there is no clear list of which version is sold by various nurseries.

I bought an ‘Issai’ from One Green World this spring, and it turned out to be the small/round fruit hexaploid variant. Many years ago, I had a long-fruit version that I think was from Edible Landscaping.

Small/round fruit variant from OGW

Long-fruit variant, photo from Edible Landscaping.
Issai%20EL

Cheers!
Hal


#2

I bought one from Ison’s and it seems to be small round.

Do you know anything about Lone Star from Just Fruits and Exotics? Is it a renamed Issai? They call for Issai for better pollination but it may just be that they are use to seeing Issia as small and round where their fruit looks more like Edible Landscaping.


#3

I haven’t grown ‘Lone Star’, but the photos look exactly like the long fruited ‘Issai’. However, photos don’t always reflect what one will actually get. One Green World has a picture of the long fruit version, but I received the small version. I assume some nurseries just use stock photos, which is why I thought I would ask what others have received.


#4

Would having the two different types help with pollination?


#5

I just looked at Ison’s site and their picture does not look like my fruit.


#6

Both types are females with sterile pollen, so probably not. However, the non-viable pollen still seems to be able to stimulate parthenocarpic fruit set, so maybe there would be some effect if they cross pollinated each other. However, the fruits are probably smaller when selfed due to not having seeds, and that would not change.


#7

The Ison’s photo is the same one used by One Green World.


#8

Very interesting, thanks for posting. I just planted an Issai this year, so can’t contribute any info yet, but when it does start fruiting I will post here. We got ours at Lowe’s, so who knows. The tag on the plant had a photo of the long fruited variety.


#9

mine is the round one im curious too JFE has a self pollinating one but different name hope it is not the same but renamed.


#10

The issai i picked up from Home Depot in 2017 looks to be the smaller round shape variant.

I notice very little amount of seeds in the pictures i have seen of the long issai variant.
This is my first year that the vine held fruit this long & im curious if the round ones will have more seeds and look more like the fuzzy kiwi interior.


#11

Both variants have female flowers that produce non-viable pollen, so technically self-pollenizing, but not self-fertile, as selfed fruits will be seedless. If the fruits are full of seeds, then there was a male pollenizer around.


#12

Just noticed this thread. My Issai came from Edible Landscaping and I just shared a photo in the link below (the second of the two photos). It’s the long-fruited type.


#13

Thanks! That confirms what I suspected.


#14

I am now in possession of a ‘Lone Star’ kiwi. I was immediately able to see that it is not either version of ‘Issai’, as it has prominent pinkish red petioles. Both versions of ‘Issai’ have pale green petioles without any red pigments.


#15

I looked at the pictures above and see the green petioles. Here is a picture I took of my Isons Issai in the middle of June showing reddish petioles.


#16

I’ve grown both Issai’s and I’ve never seen red in the petioles. I wonder if this is something that varies depending on climate or soil?


#17

I have both long and the round issai. Long has not fruited, but round is self pollinating and has fruited. Round also does not taste much like kiwi. More like hard candy with a fake taste.