The Tropical Fruit Forum

Fruit set is another area needing further research, despite all the work done by the Israelis and others.  I have some plants that have never set fruit with hand self-pollination and thus require cross-pollination.  Even the pollen source for cross-pollination has an influence.  Some crosses will not set fruit, which I assume is because the plants are too closely related.  Also the pollen source for the cross-pollination has an effect on the resulting fruit size.

yes this is common in Cactaceae, not only tropical vine genera.  it is also common for a mix of reproductive abilities within a genera.  I am not sure with Hylcoereus, but in many other genera i have work with it is common to find some species that are closely related to be self-fertile while other species are not.  In some it can happen within a single species, though are often at least considered different varieties.

Pollen source can matter a lot i think too.  I am thinking if pollination is in fact an indicator of fruit size, i wonder if it may simply be a pollen germination or pollen tube problem (which can be likely in case of hybrids).

I think you have identified the root problem.  Since Hylocereus spp. cross so easily between one another, even wild-collected plants can be hybrids.  Some of the early work by Y. Mizrahi would indicate that the species cited in his research were based upon the names provided by the germplasm suppliers.  Later works cited the ID number in the Israeli collection.

yes it big hurdle to deal with.  And the fact that early work wasnt very thorough (not to discredit, but its true) makes it ahrd to go back on sometimes.

If you are at the university, I would recommend tissue culture for the rare species.  This works well for many Cactaceae species.

I am not at university, i do study and breed cactus for many years though.  Fruit is actually my newer passion.   i work in friends personal home TC lab sometimes.  we are building new farm which will have a tc room, but i dont find it necessary for Hylocereus as it grows and grafts very easy.  It funny, when using Hylcoereus as graft stock in humid times i can actually grow callous tissue in open air in my greenhouse.  Not clean, but fun to see.  also shows that despite Hylocereus resistance to moisture, bacteria/fungal rot is still a problem.




fyliu  thank you for link, that is a very interesting site!  I will email him when we return from vacation and see if he would like to chat.  I know there are lots of people working on Hylcoereus here, maybe not like Israel.  Here more basic breeding and culling to get better table fruit.  one breeder i know is working on yellow skinned red fleshed fruit, that was a few years ago, not sure how its going.

About being self-sterile... Hybrids can have any combination of problems that prevent them from setting fruit: dysfunctional ovaries, lack of pollen, stamen too far outside the flower, flowers refuse to take pollen from the same genotype, weak pollen that take too long to travel to ovaries. If it's simply the stamen being too long, it's self-fertile but not self-pollinating. Pollen from reds tend to travel slower than pollen from whites, and that contributes a lot to red fruits not setting. You should really have a true white H. undatus to use as a pollinator.

yes that is true.  here there are numerous species and hybrids growing wild. everything hylcoereus here is open pollinated unless part of special breeding groups.  and there is little fruit set problems here.  but there are "varieties" known locally that just rarely set fruit.  they are well known and farmers can ID them (i cant).   I strongly suspect more than anything it is as simple as natural pollinators.

That is a good observation.  Moths, bats, some species of bees and even a butterfly in the Maduca genus are reportedly possible pollinators.  Another possibility is that the self-pollination trait has been cross bred into a red-fleshed type.

Yes lots of possibilities.  but i think personally that dragon fruit isnt truly self-sterile, it just has good flower morphology to prevent self fertilization.  Do the people who have to hand pollinate ever get any fruit at all if they have a number of flowers that are not hand pollinated?

This is a very common misconception - identifying Hylocereus species based on the flesh color rather than the traditional morphological characteristics of the flowers and plant.  Looking at the original descriptions by Britton and Rose, they made no such distinctions. Some of the distinguishing characteristics related to stems used by researchers are number of spines (ranging from 0 to 8 or more per areole), distance between areoles, depth of the undulation between areoles, stem color, and those that apply to the flower are too numerous to list but include flower size, color, whether or not the stigmas are forked, etc.

 

yes this is why i find it so hard.  cactus taxonomy is basically bad at best, but seems Hylcoereus classification puts a lot of weight behind rib form and flower morphology.  I have keyed out plants to find they are wrong as to their description leading me to the belief the study is incomplete/under studied (usually the case with cactus) or that all the plants we have grown were hybrids, although we used to grow wild collect seed too and still have variation outside of descriptions.  Are PDFs allowed to be posted here if we dont own them or have permission?

here, no one really knows much about the taxonomy other than those in science parks, museums or schools.  market place has Chinese varieties but their origins are barely known and people here unfortunately dont keep records well for this kind of thing, so it is commonly just said undatus = white and poly = red, which isnt very accurate i agree.

I never know about hormone treatment used with Hylcoereus, thank you for saying.  I have interest in inducing flowers in rarer cactus species which are harder to grow up form seed, so more flowers and seed better chance.


Roy, apparatus Hylocereus polyrhizus is now a synonym of Hylocereus lemairei.

As plant get reclassified they get new names but a record of the old name must remain, and is called a synonym. 
http://www.tropicos.org/Name/5100478

Do anyone know the English variety names of ones we have in Taiwan called "Yu-wen" and "I-wen"?

Skin is pink-yellow, can get up to 700g, not much fiber.  just huge and really nice eating.  but bruise easy and not ship well i dont think.  I try find English info but not have much luck.

Hello.  Next week 3 of use travel to Sabah again to see everything.  We are really hoping to try new types of durian, especially red color ones which look very amazing!  Last time we go Borneo we dont find any durian, even the more common commercial ones.  I am wondering if its is very seasonal or maybe we look in wrong places?    Our trip start in Kota Kinnabalu and we rent car and go sandakan, do river kinnabatangan and also go out to Pulau Tiga.  Are those areas have chances to try durian?

How can we find market for some of the interesting different kinds we see on internet?  So far we get to try Thailand varieties and Malaysian varieties on penninsula.  But Borneo not yet.

Thank you for any suggestions.  Unfortunately slightly too cold for Durian where I live, so we have to have import or travel to eat.