Solanum aviculare - n=23

So following on from last week, where I found out that the chemical oryzalin could be used to accelerate plant breeding by doubling chromosomes - I was attempting to find out whether I needed to obtain a Growsafe certificate in order to obtain the hazardous chemical. Well it turns out that one of my work colleagues happened to be a GrowSafe Instructor in a former incarnation, and most likely has some Surfluran herbicide in his garden shed. So he may just give me a little bit, and then I can try soaking some poroporo seeds in different dilutions this coming season to see if I can double the ploidy. Maybe polyploidy could be a good cheats way to get bigger fruit, faster!

Also today I came across a 1954 paper by Baylis in the Transactions and Proceedings of the Royal Society of New Zealand 1868-1961 which discusses ploidy in Solanum aviculare (poroporo) and S. laciniatum, and guess what? S. aviculare has exactly the same number of chromosomes as humans (n = 23)!! The other New Zealand Solanum, S. laciniatum, has twice the number of chromosomes as poroporo (n = 46). This ensures their genetic isolation. Apparently most Solanaceae have only 12 chromosomes, so this is an example where polyploidy has already occurred (allopolyploidy). Baylis makes the comment that S. laciniatum pollen is larger, its flowers, seeds and stone-cell masses (in the fruit pulp) are larger, and it has deeper corolla colour than poroporo. So this means that if I were to create a straight doubling of chromosomes using oryzalin, to obtain a tetraploid poroporo, it would probably just resemble S. laciniatum. The two aren't cross-breedable back to a triploid (46 crossed with 23, divided by 2 is an odd number, so no going there). I wonder what the maximum number of chromosomes a plant can have? Is 92 a bit excessive, do you think? What about an octoploid (n=92 crossed back with a triploid n = 46 to obtain a pentaploid n=69?). I'm not sure how this would work....

Some additional reading: "Species of this group in Australia are S. aviculare, S. capsiciforme, S. laciniatum, S. linearifolium, S. simile, S. symonii and S. vescum. The 8th species, S. multivenosum, is found in the highlands of New Guinea.
For a treatment of the group as a whole see D.E.Symon (1994). Kangaroo Apples. Solanum sect. Archaeosolanum. (D.E.Symon: State Herbarium of South Australia)."

Solanum laciniatum

Revenge to the killer caterpillars...

Brassicas are high-maintenance. I mean you can plant out a whole patch of silver beet everything runs smoothly, but Brassicas... oh boy, do they ever need some protecting from those infernal cabbage whites!
They're fine in the garden for the winter sowings because the white's simply aren't around. But from late Spring onwards it's virtually impossible to get your kales, cabbages, and broccoli through to harvest without some form of protection.

I don't like to use chemicals, like Derris dust. I would be OK with genetically modified Brassica's, transformed with a Bt gene to express itself in the young plants (killing newly emerged caterpillars at their first wee nibble), but in New Zealand I might be alone on this one. Certainly GE Free NZ and Soil & Health wouldn't share my feelings that these plants would be totally OK to human health and the environment! A good old-fashioned cloche could do the job, or caging the plants in a frame covered in bird-netting to keep the butterflies from unloading their round cargo on the young plants.

Must build something like this for next year.

For this season I've employed another method, which involves hand-plucking caterpillars and feeding them to the chickens.... not terribly effective in preventing damage, but revenge is a dish best served wriggly...

Truffles via Agrobacterium rhizogenes - of course!

I have been musing on how one would go about getting truffle fruiting bodies to form on agar plates, in vitro, and came across a section in Ian Hall's latest book (Taming the Truffle: the history, lore, and science of the ultimate mushroom, co-authored with Gordon Brown and Alessandra Zambonelli) which describes a technique for doing just this.

It would be fair to say I've had a wee obsession with truffles ever since I read The Black Truffle (also by Ian Hall) in my university years. Truffle oils are definitely more in my budget than the real thing, so I can only imagine what they might taste like.  But as to growing them myself - then the whole delightful venture takes on an appearance mid-way between science and magic! The first truffiere set up in New Zealand was in my home town Gisborne, and produced truffles within 5 years of planting. This is really fast - many more truffieres have been planted around the country which are still waiting on their first treasure.

Growing truffles on agar plates is quite possibly a holy grail - ingeniously dispensing of the need to inoculate roots of living trees with the fungus, and all of the orchard set-up and ongoing management.  Instead, infected root is produced using transformed roots which are able to grow without an attached shoot. This kind of system has also been used for arbuscular mycorrhizal fungi, and is described by Varda Kagan-Zur (2006) and colleagues. Derooted rockrose (Cistus incanus) seedlings are inoculated with Agrobacterium rhizogenes, a bacterium that carries the Ri (root-inducing) plasmid which induces root galls on some trees. The roots then produce thin, delicate hairy roots 8-11 days after inoculation, and can be transferred individually to liquid culture medium containing antibiotics.

The inoculated roots are then grown on a solid culture medium containing lower concentrations of antibiotics and nitrates, and transferred to solid media capable of supporting the endomycorrhizal association.   A piece of agar containing actively growing perigord black truffle hyphae is placed in the middle of a bunch of hairy roots growing on solid medium and voila! after 3 months, mycorrhizae forms in the elongated roots, and about 2 months later, short, club-like root forms can be observed. These are then further encouraged to produce truffles, probably even in a commercial way.

Heck of a lot easier than asking a sow to give it up once she's sniffed one out too!!

IAPB - Plant Biotech meeting

I'm just back from Hanmer Springs, where I attended the 19th New Zealand branch meeting for the International Association for Plant Biotechnology. Just loved it! There were some really great presentations on tissue culture, plant developments and new technologies in plant breeding, and Hanmer Springs is the most incredibly scenic place.

I mentally refreshed some of the techniques I used during my time as a Research Associate at AgResearch many years back - using plasmid vectors and restriction enzymes to clone DNA, and PCR to check whether all the pieces went together in the right order. Someone asked a very good question in one talk about whether concatemers were formed, and I knew what they were talking about! My AgResearch work used electroporation techniques to then get the plasmids into E. coli and Mycobacterium bovis (or bovine Tb). But plant transformation uses completely different techniques of course - neither of which I have tried yet. The biolistic guns methods look especially cool - perhaps science would appeal more to school kids if they got to see some of these guns shooting DNA-covered pellets into plants to transform them!  The 007 approach to modern day science!

Another presenter showed how oryzalin can double the somatic chromosome number in plants, from diploid 2n to the tetraploid in Sandersonia, which completely altered the plant's architecture. These were then crossed back with the 2n to obtain an infertile triploid which looked pretty marvelous. I wondered whether this might be a good option for increasing fruit size in my poroporo? Oryzalin is apparently found in the herbicide surfluran, which apparently cannot be bought over the shop counter. I might need to obtain my GrowSafe certificate in order to buy it and use it, so I'll investigate this a bit further.

Another brilliant presentation was the production of mature stigma-like structures from saffron in vitro (on agar plates basically), which release an exudate containing compounds associated with the saffron taste (picrocrocin), aroma (safranal) and colour (crocins) in very pure form.

Another talk discussed the potential for removing viruses, phytoplasmas and bacteria through cryotherapy (a two-step cooling process getting down to temps of -35 to -40 degrees Celcius), where ice nucleation crystals kill the pathogens. This could be useful! And another brilliant talk on micrografting in apples to reduce the breeding time - now that the apple genome has been sequenced and a huge deal of work has been done in mapping the genes and QTLs.

Very inspiring to get among plant scientists again and have a jolly good geek out, and of course enjoy the wonderful surroundings of Hanmer, the hot springs, sunshine and beautiful scenery!