Though we are often taught in highschool biology that A x B is identical to B x A when plants cross, the reality is that is often not the case. And in many cases the different sides of a single cross is radically distinct.
Here we have a case of a diallel cross where the sides are, once again, radically distinct. This one was tricky because one of the plants involved is a specimen of Trichocereus grandiflorus, which has a lot of synonyms incidentally, which is variegated, so it is called VRG for Variegated Red-flowered grandiflorus. When this plant is used as the mother the seeds germinate well enough but they do not grow well because they often lack chlorophyll. Out of more than a hundred seeds planted in this container on one side very few of the seedlings were able to grow and they do so with considerably difficulty and slowly.
On the other hand, the other side of the cross is a plant called Malo4, it is a Trichocereus hybrid having T. scopulicolus and T. huarazensis genetics in it, which are essentially both distinct forms of the plant commonly called Trichocereus pachanoi. When this plant is used as the mother the seedlings germinate and grow quite well.
In this image we can see the seedlings with the VRG mother and Malo4 as the father in the foreground of the image. These are the exact same cross as the taller plants behind them, which are the same age and have been grown in the same conditions. The seedlings in the back had Malo4 as the mother and VRG as the father. All plants are depicted at six months after germination.
You can see that the two sides of this diallel cross are extremely different from one another. Once again here is an example of seedling showing that A x B is, in many cases, not the same as B x A when it comes to plants. It is noteworthy that this cross is one that can be considered as an interspecific cross, with each parent representing a distinct cactus species in the same tribe or clade of cacti. I'm using the specific epithets or species names most commonly employed by those who study these plants, but as mentioned they have synonyms and can both be considered Echinopsis. Interestingly, the VRG is a day blooming plant with a red flower, which grows much shorter, rounder and has more ribs than Malo4, which is a night blooming plant which grows much taller and more slender and with less ribs than VRG.
Of note is that in both cases of the examples I share in this thread, the plants with the shorter many ribbed rounder mothers are in fact shorter, have more ribs and are rounder, while the opposite is true when the mother is a taller, thinner form with fewer ribs. This is not uncommon with regards to these types of crosses.
Plants like these are commonly used for breeding to attempt to combine the traits of a large night blooming flower from things like Malo4 with the smaller, day blooming colored flowers from things like VRG to result in a plant with gorgeous colorful and large day blooming flowers that is much smaller and more manageable than the taller parent. I have to thank the breeder for the quality of their seeds, I think they are the most interesting cactus seeds on the planet at this time.
