Homemade Hybrids:

Using cement and MSG for evolutionary innovation

In the interest of spreading plant breeding techniques to as many growers as possible, this article highlights two simple, easily-accessible methods. Individually or in combination, these can be useful in developmening new crop diversity. One (cement powder) promotes the success of distant crossing, and the other (monosodium glutamate) is for inducing mutations and polyploidy (doubling the chromosome number).

Wide hybridization—the crossing of distantly related species—holds a lot of potential in plant breeding. Sometimes it’s only a matter of getting the timing right, making some pollinations, and growing out the seeds.

However it’s often more of a high hanging fruit situation, requiring painstaking work to get past crossing barriers. For the breeder, the extra effort may be rewarded with novel traits and adaptations. Luckily, these barriers can be flexible and susceptible to bypassing. Cement powder turns out to be one way of getting across some initial barriers, in particular fertilization and fruit formation. In the cacti growing community, people have been reporting success with cement since around 2012. In the Cactaceae family in particular, some species from different genera can hybridize readily, but in other distant combinations the flowers drop off soon after pollination. Using the “cement method” or “cement pollination,” several new intergeneric hybrids have been obtained in the cactus family. The basic technique: Apply a tiny of bit of cement powder to the stigma 30 minutes prior to the distant pollen (repeat the process). Experimenters have confirmed that other high pH powders such as CaCO3 can be used similarly.

Note: this technique can be used to break both self incompatibility and out-cross incompatibility. There are some shared mechanisms preventing both kinds of pollination, therefore some methods can break both kinds of incompatibility.

The original thread and instructions:

“1. Get yourself some Cement from the DIY Store. Very fine powder. The finer the better. But the typical Commercial grade works fine as well.

2. Get yourself a small brush and apply some of the cement dust on the Stigma of the flower on the plant that you want to produce seeds with. Also try to blow a little bit of the dust inside the flower.

3. Cement works as some kind of irritator that makes the flower create some Anti-Bodies that enable her to accept her own pollen.

4. Then wait for half an hour and brush some of the own pollen on the flower and repeat this numerous times.”

Pretty simple! A friend of mine at Urban Food Forest tested the cement method on shark fin melon (Cucurbita ficifolia) x watermelon (Citrullus lanatus) this season, and reported that with the cement method the ovaries (the base of the flower) began to develop and swell for a few days before the flower dropped. Without cement, the flowers didn’t show any sign of fertilization and dropped promptly the next day. This simple, cheap method deserves broad experimentation.

MSG to induce polyploidy. Another helpful household ingredient for the plant breeding toolkit is the umami food flavoring monosodium glutamate (msg). Msg has been recently used by researchers in India as a mutagen to generate polyploids and novel variation. Polyploidization, the doubling of chromosome number, is used in plant breeding for various purposes such as increasing stress tolerance, vigor, fertility, and plant size. As a result of this mutagenic process, novel variation also can appear. Polyploidization is a crucial tool in wide hybridization, used to restore fertility to sterile hybrids.

Photo of hybrid passionfruit seedlings: typical diploid leaf on the left, larger darker polyploid leaf on the right. These seedlings are all from the same seed parent, but the polyploid outgrew and out-flowered all the rest of the (~30) diploids. In this case the polyploid appeared spontaneously and not as a result of treatment.

One of the most commonly used chemicals use to induce polyploidy is oryzalin, a commercial herbicide. It’s therefore astounding that a food ingredient can also be used to generate polyploids. The ease of acquiring and handling msg opens the door for many more gardeners and independent plant breeders to experiment with it. There are many minor root and tuber crops for example where increasing their size would make a significant difference in the crop’s utility. Wild species can also benefit from this process, which can speed up selection and domestication.

Here is the protocol (source):

“Uniform sized fresh bulbs of Urginea indica Kunth (Fig. 2) were selected and their roots were removed completely  with scalpel. Five different concentrations of Monosodium Glutamate were prepared, viz. 0.1g/l, 0.2g/l, 0.3g/l, 0.4g/l and 0.5g/l. The bulbs were then soaked discretely in different concentrations of Monosodium Glutamate for six hours, subsequently the bulbs were washed carefully with running tap water for few minutes. Finally, the treated bulbs were planted in the prepared plots to raise M1 Generation.”

It’s interesting to note that more polyploids appeared in the second vegetative generation after soaking in msg (M2 vs M1). In this experiment, the lower concentration of .2g/l msg was the most successful in inducing polyploidy. Higher concentrations up to .5g/l were too mutagenic to efficiently generate polyploids. They end the paper with a discussion of the need to develop ideal msg concentrations for various different species. They subsequently made msg polyploids with another medicinal bulb Drimia indica (source). Protocols for the msg treatment of seeds and shoot tips should also be developed. Selecting out the polyploids generally involves looking for larger thicker leaves. Microscopes are used to count a more precise number of chromosomes. Sometimes recently converted polyploids are slower to get growing at the beginning, but they frequently end up outpacing diploids.

We have discussed some of the reasons to use polyploidy in breeding, such as restoring fertility to a newly created distant hybrid. The combination of polyploidy and hybridization is called allopolyploidy, which took place many times in crop domestications such as in sweet potato, wheat, peanut, quinoa, rutabaga and others. Another reason to generate polyploids that you may not hear about as much is to induce plasticity. The process of polyploidization, and strong stressors generally, cause genome shock to an organism. This can help a crop adapt to novel conditions, such as acclimatization to a new ecology. With continued cultivation and stabilization of the variety, plasticity will then decrease—the jumping genes are quieted into dormancy by epigenetic mechanisms. In the context of graft hybridization, plasticity is important because the genome instability promotes trait transfer from across the graft union. It may also help with increasing distant graft compatibility. The traditional recommendation has been to use hybrid seed for mentor grafting, again because of the genome instability. If for some reason hybrid seed isn’t able to be used, soaking seeds in msg could be an acceptable substitute. See this essay on for more information on the technique of graft hybridization.

Stay tuned for more discussions of simple DIY plant breeding techniques !