herbaceous grafting and genomic shock in plant breeding

[agrorev]

Grafting in general is a tool for propagation, disease resistance of rootstock, or novelty (tomtato).  For a good discussion of the uses of grafting in plant breeding (not propagation) look into Ivan Michurin's writings.  One possible use of an herbaceous graft in plant breeding could be grafting yacon onto a sunflower to initiate flowering in order to harvest pollen or attempt a cross earlier in the season than normal.  The shock of grafting can cause the scion to flower in some cases.  Grafting can also be used to influence and transmit characteristics.  This can be minimized or maximized depending if parents are more homologous or more wide hybrids, age and size (altered by plucking or leaving leaves) differences of the stock and scion, and the amount of time of the graft, or if the plant intended to be influenced has been shocked or destabilized in some way by for example recently induced polyploidy.  These factors have to be combined together in an intelligent way for this to work from what I gather.  Wide grafts that would otherwise fail can be achieved if the plant is a new hybrid or otherwise shocked into "plasticity," when its means of genetic control and suppression of transposable elements are disrupted.  If you are trying to influence a wide hybrid plant through grafting and that hybrid is a 30 year old tree however, its developmental genetics will have stabilized to the point that there will be but a very minimal influence by grafting.  Grafting a shocked plant thats in a receptive/plastic state onto a wild relative will have a degrading influence, making the cultivar deviate strongly towards the wild one.  It may be possible to do the reverse by careful arrangement of causes/conditions, but the wild types seem to have in general an intrinsically unilateral influence (often true with seed hybrids also).  For most perennial veg. type plants we will probably want to use an herbaceous approach graft plus a humidity dome.  These types of techniques should be combined with others such as pollen mixtures, bud pollination, polyploidy etc. for the most effect and widest application.  Imagine for example grafting a skirret seedling recently shocked by polyploidy conversion (since we can't shock it by crossing) onto say arracacha.  It may fail, but according to these principles, it should have a higher success rate.  Least likely to work would be a older skirret (either diploid or polyploid) that has been propagated vegetatively for a long time. 

Discussion of herbaceous grafting from 1895, when they seemed to be a lot more adventurous with different grafts.  Also mentions the disproportional influence of wild types.  Root grafting was reported most successful for herbaceous plants: bulbnrose.x10.mx/Heredity/Daniel/Daniel1895.html

Link to summary of Michurin's principles and methods.
www.ias.ac.in/jbiosci/mar2011/13.pdf‎

[nicolas]

Very interesting, thanks agrorev ! Your examples make me dream

Grafting to induce flowering/seeding have just be noticed for potatoes in a HG thread

[starry]

Great info!

I wonder if grafting squash onto buffalo gourd would help with successful crosses?

[nicolas]

Maybe that grafting on the same variety (or even on the same plant !) could at least synchronize flowering, if no more.

[starry]

I vaguely recall reading somewhere that Michurin would use grafting as a technique to aid in wide crosses. I'll see if I can locate the reference.

[agrorev]

fruit snacks, I found a reference to preliminary vegetative approximation with cucurbits in Selected Works, p. 160

As another case in point, let me quote an instance when two plants of different species were crossed following preliminary vegetative approximation by grafting...Seeds of the Nerosimy cucumber were planted in a hothouse frame on Feb. 24, 1924, they sprouted on Feb. 28. On March 15th, for the purpose of vegetative approximation, sprouts of the hybrid noodle squash (complex hybrid of Cuburbita pepo x Cucumis melo backcrossed to melo multiple times) and of the Kommunarka melon were grafted respectively onto the axial shoot and the two main branches of the cucumber plant. At the time of grafting, the cucumber plant had 5 leaves, while the squash and melon seedlings had only fully developed cotyledons. The stock and scions joined very quickly, the grafts soon began to grow and develop runners, which, after being pinched off at the third leaf, produced flowers on May 20.

These were fertilized after careful castration--20 melon flowers with squash pollen and 12 squash flowers with cucumber pollen. Of this number only one melon and one squash flower successfully produced fruit on the cucumber-runner as stock. As the fruits developed, the melon ovary deviated greatly from the maternal form: the resultant fruit was small, green in color and of conical shape, coming to a point at the calyx end. It contained 31 seeds of peculiar bevelled form. In the case of the squash fruit, the only manifest change was that it was half the normal size, with 40 seeds circular in shape and half of the usual size.

Some historical/conceptual background:
Darwin's Theory of Epigenetic Inheritance

Nonrandom directed mutations confirmed
They are referring here to experiments on bacteria, but idea applies to higher organisms.

Cairns and colleagues concluded their 1988 review on the origin of mutants as
follows [3]: “Curiously, when we come to consider what mechanism might be the
basis for the forms of mutation described in this paper, we find that molecular
biology has, in the interim, deserted the reductionists. Now, almost anything
seems possible In certain systems, information freely flows back from RNA to
DNA, genomic instability can be switched on under conditions of stress, and
switched off when the stress is over, and instances exist where cells are able
to generate extreme variability in localized regions of their genome. ”

[nicolas]

That come to mind :



In french "greffe par approche". I dont know the english term.

Here an herbaceous graft (with tomatoes)

www.greffer.net/?p=107

[agrorev]

Selected Works P. 167

THE TECHNIQUE OF CROSSING INDIVIDUAL PLANTS

In hybridization when crossing plants belonging to different species, particularly if they are distant ones, I have been using a completely original method that has never been used by anyone else. This method gives much better results than the simple methods of crossing formerly used which in the majority of cases prove to be utter failures. My original method has been elaborated on the basis of the considerable changes that the properties of a small part of a young plant (a cutting) undergo when grafted onto a crown of a different variety. These changes take place under action that entire root and leaf system of the latter exerts upon a very small part of a young plant that is rather unstable in respect to various changes. (By this method vegetative hybrids are most easily obtained, if the grafted cutting is kept under such influence for 3-5 years then transferred on a separate young stock.) I use this vegetative change as an auxiliary means of approximating two different plant species so as to obtain a sexual hybrid by crossing them in the future.

THE RESULTS OF CROSSING VARIOUS SPECIES AND GENERA

This is the secret of my success in obtaining interspecific plant hybrids, such as crosses between the apricot and plum, sweet and sour cherry, Pyrus salicifolia and the local cultivated pear varieties; between the various species of walnut, the various species of grapes, the various species of quince; between the pear and the mountain ash; between distant species of apple; between species of currant and other small fruit shrubs; between pumpkins and muskmelon, musk and watermelon; between the various species of lilies; between Physalis and tomatoes, etc.

Therefore in the cases where simple crossing between different species of plants failed to give good results, the introduction of preliminary preparation by means of vegetative approximation helped me to produce more than a hundred new varieties of plants. Besides a number of plants hitherto unknown to our region have been introduced into culture. Half of these new fruit and berry cultures will be suitable for the Northern districts of Russia and Siberia, whereas the second half may serve to increase the number of selected excellent varieties in the central part of European Russia. Thus, there is still the possibility of considerably pushing northward certain varieties and species of plants, since these new varieties when raised from seed in our region and grown under the constant influence of its climatic and soil conditions have proved to be quite stable in our parts.

THE DETAILS OF THE METHODS OF CROSSING INDIVIDUAL FORMS

To make these clear I shall dwell in greater detail on the working of my method. When a simple cross between parents belonging to different species fails to take place, preliminary vegetative approximation is effected. This is done by taking cuttings from a one- or two- year old seedling belonging to a certain species, preferably a crossbred (that is a plant that is a hybrid itself) and not a pure species type; several cuttings are always taken, since not every individual possesses the ability of coalescing with plants of another species. In the spring these cuttings are grafting by means of a Geissfuss onto several branches of a mature (about 10 year old) tree belonging to a plant of a different species--a parent plant in the future. Here the grafts develop and are gradually altered in structure under the influence of the entire root and leaf system of the tree up to the first simultaneous blossoming of both species; this is the time when a more or less successful crossing is effected. The is no need to be discouraged if the cross fails to take place at the first blossoming or if the seeds obtained from the cross fail to germinate, since after the second bearing on the following year, these defects almost always disappear, with very rare exceptions.

The same method, only taking into account the short cycle of development, may be applied to annual vegetables; cuttings taken from the end shoots of one species are first grafted into slanting notches on the runner or shoot of a more vigorous plant of another species, for example, a muskmelon or watermelon grafted onto a pumpkin, Physalis on a tomato, a tomato on a potato, etc. (but not the reverse), and after than a sexual cross between the two species is effected.

[starry]

Thats the one I was thinking of...thanks agrorev

[agrorev]

It would probably make sense to use "preliminary vegetative approximation" prior to crossing in the case of the Phaseolus and Cucurbita crosses we've been discussing in the other threads. If we are going to induce polyploidy prior to doing the interspecific cross, we might as well do the reciprocal grafting before crossing since the polyploid seedlings will be already in a state of genomic instability.

[agrorev]

www.youtube.com/watch?v=iWs48z-UPkQ

The cellulose paper/hydrofilm he uses makes total sense: its breathes but keeps in moisture. Herbaceous grafts, besides the approach graft, are virtually bound to fail otherwise through humidity loss. It still must be out of direct sun. He says to not take the hydrofilm off abruptly but to drill holes through it as the graft starts growing then cut the paper off later.

[nicolas]

It seems that grafting could also induce changes in the seeds and some traits could be heritable !

Helianthus tuberosus, Xanthium, Cirsium, Carthamus and Matricaria were successfully grafted on sunflower. The reciprocal grafts gave a lower survival rate. Even in the year of grafting the seeds formed differed from those of the initial plants in shape, colour and oil content.

www.cabdirect.org/abstracts/19731609869.html

In addition to maize, referred to below, heritable changes were induced by graft hybridization in sunflower, radish, beetroot and tomato. The young plants were in each case grown on their own roots and supplementary roots of another variety. Maize plants which developed from dent scions grown on their own roots and on supplementary roots of a flint variety produced ears with 39.4% flint grains on selfing. The reciprocal graft had ears with 73-9% dent grains.
www.cabdirect.org/abstracts/19631600140.html

Grafts of Helianthus occidentalis (perennial) on annual sunflower varieties altered the leaf and seed type of the stock and increased its vegetation period. When annual varieties of different vegetation period were grafted, an effect was observed on the scion; alterations in the oil content of the scion were also observed. Abnormalities were observed also in the progeny of the grafted plants.

www.cabdirect.org/abstracts/19421600223.html

"vegetative hybridation" give interesting results

Maybe one could perennialize an annual solely by grafting on perennial rootstock and save seeds ?

[nicolas]

grafting can influence the rootstock/tubers too

Grafts were made of Smyslowskii (Fürstenkrone) and Katahdin on Wohltmann, a variety very rich in starch; grafts of Wohltmann on Wohltmann served as control. Grafting with Fürstenkrone caused several alterations in the tuber shape, whilst grafting with Katahdin produced no such changes. The plants arising from the altered tubers from the grafts with Fürstenkrone gave rise to plants which also differed from the controls, and the tubers they produced bore a still stronger resemblance to Fürstenkrone than those of the first year. They contained 3-5% less starch than the controls and were 25-30 days earlier in maturity.

Grafts were made of Solanum demissum on Wohltmann and Alma. The tubers of the grafted plants gave rise to plants which showed no morphological deviations from the maternal type but proved to be resistant to phytophthora in the field and were very little attacked when artificially inoculated. Grafts of Alma on to S. demissum produced a number of suckers from the rootstock, and some of these were used as cuttings to produce new plants. The plants produced had 48 chromosomes and were of the cultivated type, though showing certain characters of S. demissum, including blight resistance; their tubers were deep bluish-violet in colour, thus differing from both parents but resembling sexual hybrids between the two. The plants obtained from these tubers were also pigmented. No such changes were observed when Fürstenkrone and Lorch were grafted on S. demissum.

www.cabdirect.org/abstracts/19441600236.html