Building with Brix

Although tomato fanatics will argue on relative taste of various tomato varieties, it is generally recognized that there are three major components to taste in tomatoes: sugar content, acidity, and volatile flavor compounds (reference).  The right balance of sweetness and acidity is crucial, but generally higher sugar content makes  for better tasting tomatoes (reference). Sugars are the predominant component of soluble solids in tomatoes.  Soluble solids content (Brix units) is easily measured with a hand held refractometer. 

Brix level in most tomato varieties varies between 4-6%, with popular cherry hybrids like SunGold and Sweet Million being notably higher.  To boost soluble solids content in tomatoes, breeders have recently incorporated genes from wild relatives.  This has resulted in a new generation of super sweet tomato hybrid cherry and grape types with reported >10% Brix.  Many of these new hybrids also contain the rin gene for longer shelf life, and have improved resistance to fruit cracking.  Seed for most of these is only available to commercial growers, so thanks to my various Tomatoville friends for helping us to access seed this winter.

This summer we are growing out F1 and/or F2 generation plants of several new super sweet grape/mini-plum hybrids for crossing to our best striped cherries, saladettes, plums, hearts and beefsteak types.  We hope to incorporate higher Brix, longer shelf life and improved disease resistance from the commercial hybrids to our “heirloom derived” breeding lines.

  

TGRC photo

A particular TGRC accession of S. galapagense (L.cheesmanii minor) from the Galapagos Islands has been reportedly widely used as a breeding source for high soluble solids.  In this research study (publication link) LA530 tips the scales at 13% Brix, more than double any of the commercial cultivar checks.  We are also growing this beast this summer, probably making a few crosses, but mostly out of curiosity.  Note the strikingly different fruit type.  Seedling vigor is also unique, and not in a good way.  An interesting side note is that LA530 also has high salt tolerance and under salty conditions gets even a little sweeter!

Taste is not all about Brix, but we are betting high Brix is a good building block for improved flavor (pun intended).  We should have F2 populations from these new crosses to taste test in 2012.

Pine Mushroom Season

Last year Pine mushrooms made me make a delightful pasta dish. This year it wasn't much different and the delights went with some other mushroom

and this

and this from the balcony garden

and turned into this.

YUM! I love Pine Mushroom season at the Victoria Markets (even if they are a little expensive.)

Crazy Cukes

Before we hit crazy cuke land let's remember what a normal one looks like. This is a usual bush cucumber that I grow.

And here are three of a normal variety that I also grow.

And now there is one crazy cuke - my lovely piggy tail cucumber. Here he is growing, just to prove there was no tampering. His uniqueness was just mother nature having a giggle.

And then, finally, I picked him.

He was enjoyed in a salad both last night and today. Inside him was a sweet and slightly oversized-seed-filled centre, no different to the straight cukes. I love mother nature's little oddities. Any random growings in your gardens this year?

Harvest Monday

I am so so so close to getting the first full draft of the thesis done, but yet so far from the end goal. In the meantime here is what I have been harvesting of late ...

There have been cucumbers, plenty of cucumbers, enough that I have to eat them every day to keep up, but here is just one. I am going to post soon about the world's funniest cucumber which is shaped like a piggies tail but for now it is normal cucumbers.

The seeds were a little big, maybe I left it on there too long, but it is hard to keep up with them. Tasty in a salad.

That was my lunch, these little red lovelies went in something else,

my breakfast!

I have been going through a phase of eating fruit salad in the morning, usually blueberries and rockmelon with whatever else is affordable at the markets. It was lovely to be able to supplement it with my own home grown strawberries.

In the garden harvest there were eggplants and beans, both of which made it into curries.

I am planning on trying salt and pepper eggplant with some of the rest. I have been harvesting chillis to give to friends, basil leaves for lasagnes and silverbeet as needed. Even in this strange weather it seems to be putting out some good food. With more eggplants, the crazy corn possibly beginning to come good and the figs turning colours it might be an interesting harvest next week. For more harvests from around the world pop on over to Daphne's Dandelions.

Breeding for the Blue Tomato

Our darkest F2 fruit

Blue tomatoes, not really - the fruit are really more of an indigo color; the pigmentation more like an eggplant.  So what's the fuss about and what's the genetic basis for the accumulation of anthocyanin pigment in tomato fruit?  Here's what we've learned from the literature and from our experience in breeding for the trait.

In the last several years there’s been significant interest in breeding tomatoes with improved nutritional quality.  One approach has been to increase fruit concentration of anthocyanin and related phenolic compounds that also have anti-oxidant activity.  Professor Jim Meyers, and various graduate students working with him at Oregon State University (including Jones, Mes, Boches and Dalotto), have used TGRC lines to introgress, into cultivated tomato, two genes from wild relatives that independently regulate anthocyanin synthesis in tomato fruit.  This group has published most of what is known about the genetic basis for the trait (see Jones, 2003 link).  We are among a group of several tomato breeders working on incorporating these genes into various tomato breeding lines.  The Aft/atv parent we used in crossing was a single plant selected in our breeding nursery from OSU Blue for intense anthocyanin accumulation in the fruit and acceptable horticultural type.  Taste of this OSU Blue "donor plant" was not very good.

Aft fruit cross section - pigmentation
accumulation limited to surface
layers of cells  (P. Boches photo)

The Aft (anthocyanin fruit) gene, from S. chilense, is a regulatory gene (An2 transcription factor) that is induced by UV light and that triggers up-regulation of anthocyanin biosynthesis in tomato fruit, and to a lesser extent in vegetative tissue.  In Aft plants anthocyanin accumulates in and just below the fruit epidermis, where light penetrates the first few layer of cells.  It is believed that such accumulation is a stress and protection response to UV light (think melanin accumulation in human skin cells in response to UV light – tanning).  Typically those parts of the fruit exposed to light will accumulate anthocyanin and turn black/purple, while those parts of the fruit not exposed to light will have the normal background fruit color.  Anthocyanin accumulation begins very early during the green fruit stage and masks normal fruit color in mature fruit.  Anthocyanin appears to accumulate preferentially in the green stripes of gs and Fs fruit.

 Todd Dalotto photo

The atv (atroviolaceum) gene, from S. cheesmaniae, induces anthocyanin accumulation in vegetative tissue and, in combination with Aft, to anthocyanin accumulation in tomato fruit.  Plants homozygous for atv accumulate anthocyanin in leaves, stems and petioles, especially in conditions with high light and cool temperatures. 

Co-expression of Aft and atv have a synergistic effect on fruit anthocyanin production (see Povero 2012 link).  For this reason a breeding program for anthocyanin accumulation in tomato fruit needs to select for both Aft and atv.  Here’s what we have learned from evaluating several hundred plants from six F2 populations segregating for both Aft and tav:

Under cool high light conditions seedlings homozygous for atv will begin accumulating anthocyanin in the cotyledons and the epicotyl.  This accumulation will become more obvious as the seedlings get larger.  Maintaining cool temperatures and high light is critical for successful selection of atv/atv seedlings at this stage.

F2 seedlings segregating for
pigmentation in cotyledons

This dark purple PL seedling did not produce

fruit w/ any anthocyanin pigmentation

Once the seedlings establish in the field and the temperatures increase, the anthocyanin accumulation in leaves/stems fades quickly.  Later in the season when the temperature begins to drop, anthocyanin accumulation in vegetative tissue (especially growing points) starts anew.

Differences in pigmentation at transplanting within a F2 family,
each selected weeks earlier for seedling "purpling"

Some of seedlings with the darkest “purple” foliage had no anthocyanin accumulation in the fruit (atv positive/Aft negative).  In fact there was no significant relationship between seedling score for anthocyanin and anthocyanin accumulation in fruit.  This was a surprise, and suggests not being too rigorous in screening seedlings.  In 2010 we selected < 5% of the F2 seedlings for transplanting – based on the anthocyanin phenotype in seedlings.  This is probably more severe than needed.  Among seedlings showing some anthocyanin acculation, there is a considerable variation in degree of purpling (see photo above).  This may be an interaction between atv and Aft or other unknown genes.

Early fruit pigmentation 

Pigmentation is local and only where fruit is exposed
to direct sunlight

Anthocyanin shading on the sunny side of this F2 fruit

4    Anthocyanin accumulation in fruit (primarily due to Aft) begins very early in fruit development – but only in young fruit exposed to light.  Because early fruit is often deep in the canopy, we do some early pruning to improve light exposure, enabling the Aft phenotype.  Late in the season, with better fruit exposure to sunlight and cooler temperatures, we saw stronger expression of the Aft phenotype.

5    Among F2 segregants showing some anthocyanin accumulation in fruit, there was very significant variation in early season intensity of the pigment, and how sensitive such accumulation was to light.  Part of this may be due to whether Aft was homozygous vs heterozygous (i.e. partial dominance – suggested by Jones), but it appears there may also be interactions with other unknown genes.  We should learn more from the F3 generation.

Our best tasting F2 - a bicolor orange w/ indigo highlights

6    In the F2 generation there didn’t appear to be any relationship between anthocyanin accumulation in the fruit and flavor/taste.  Taste of fruit from the best F2 plants with a strong Aft fruit phenotype were 7.5-8.0 on a scale of 10.  There’s still some work to do here.  This year we will have F3 progeny from the best Aft lines and backcrosses of these to our best tasting non-Aft breeding lines.

Aft/gs

Indigo striped cherry

      As described in our “Genetic control of fruit stripes” blog, we saw a preferential accumulation of anthocyanin in green stripes in fruit of F2 plants co-segregating for gs and Fs.  This should yield some pretty interesting and novel looking F3 fruit in Aft/gs  and atv/gs plants with various fruit color/shape combinations.  Purple Dragon is Dean Slater's name for a F3 line combining Aft/gs.  Black and Brown Boar was the striped parent in the F1, which I think is evident here.

Late season w/ plenty of light exposure to fruit and cooler temperature

High pigment mutants hp1 and hp2 dg are lesions in regulatory genes (transcription factors) that regulate light-signaling in tomatoes.  Homozygous hp plants show several novel developmental and metabolic phenotypes, including increased fruit pigmentation and accumulation of various flavonoid phytonutrients.  A combination of hp1 or hp2 dg with Aft and atv show >20x enhanced anthocyanin accumulation in tomato fruit, see photo here.  The hp  phenotype generally also results in negative effects on plant vigor and fruit yield.  The combination of hp and Aft/atv is subject to a U.S. patent application (patent application link).

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Here's a 2012/13 update.  With a few exceptions it appears that to get exceptional flavor in an Aft/atv line it will require two generations of crossing (a cross and a backcross/modifed backcross) of P20 to a high flavor parent.  We have several nice MBC1 lines now in the breeding program  One exception is the Indigo Tiger cherry shown above and now in the F5.  In 2012 I planted the new OSU release Indigo Rose (OSU press release).  Good anthocyanin expression but flavor was just fair, not good enough for me to want to plant again.  I've also tried several of Tom Wagner's Aft lines and found a few interesting plants in these widely segregating populations.  One of the best was a green when ripe (GWR) line with anthocyanin stripes, from a line he called Muddy Waters.  We used this in several crosses in 2012, and some interesting F2s from these in 2013.

Selection from Muddy Waters

MW x GWR breeding line - F2

We had a chance to visit Brad Gates (Wild Boar Farms) in 2012 and he had several Aft/atv lines, including a couple of ours.  Here's a photo from his nursery of an Aft line tracing to a breeding line of ours we call Freckled Strawberry.  Note the indigo freckles and shoulder on this unripe fruit.  The bottom photo is from a similar Aft Freckled Stawberry line from our 2013 Pennsylvania nursery - top fruit from within the canopy (no light, no anthocyanin) and bottom fruit exposed to light on one side with anthocyanin present.

Aft Freckled Strawberry

We've found another interesting manifestation of Aft/atv in a segregating breeding line tracing to our cross P20 x Beauty King.  Note the "tiger stripes" pattern.  Although we are yet unable to stabilize the phenotype, anthocyanin accumulates in lateral stripes on developing and ripe fruit (coexpression w/ Fs gene).  The Fs phenotype appears to be highly influenced by environment, complicating the breeding.  This photo is also from our 2013 Pennsylvania nursery - nickname for now is Bengal Tiger
.

Bengal Tiger

Wet Weather and the Balcony Garden

Overnight we have had rain, not a lot, just a light and steady smattering which means I won't have to water today and possibly even tomorrow (depending on if the sun comes out and if the wind stays away.) This gives me a good 20 minutes in my day in which to blog. With the final few memoirs for the thesis to be read and significant other work on my life has been busy. A little too busy for a regular blog and even too busy to remember to photograph things in a timely manner. Time management skills can only work for 24 hours in a day and until I master the art of getting 36 hours out of a day I will have to make to with these little snatches of spare time. But yay to now getting to post.

I love when it rains. Just look at the picture above of my lovely little chilli all covered in drops. Not only is the hand watering a non-necessity, I get to sit by my large windows and watch the rain fall onto the garden. Drops collecting on the green (and slightly yellow) plants, pooling into their soil. A few hours later they look taller, stronger, happier. Rain just has this natural boost for plants that they simply cannot get from tap and/or grey water. Mind you this summer has been the wettest on record, and it hasn't been that good for many gardeners and farmers. Some had their crops and top soil washed away while others like stone fruit growers were damaged by wind and hail. It has also caused a few problems in the little balcony garden, such as increased risk of powdery mildew, problematic pollination and issues with drainage. What are these problems, how have I gone about fixing them and what do these excessively watery days mean for balcony gardeners?

1. Powdery Mildew

In a warmish moist environment powdery mildew is pretty much a given. Zukes, Cukes and others in that family usually fall victim to it. The picture below shows the beginning of it on a yellow zucchini (if you strain your eyes.) White dots appears on leaves, under leaves and on stems. They slowly defoliate the plant and kill it.

Though hard to prevent it is pretty easy to control. I have always used a milk spray, one part whole milk (skim, lactose free which I have in my tea won't cut it, it has to be the full cream stuff) to 9 parts water. This ratio makes it work for my balcony garden though you might have to tweak it for yours. Spray all affected areas including the underside of leaves and stems on your plants in the morning and the evening and the powdery mildew tends to fix right up. It also helps to remove any really badly affected leaves and dispose of them (no composting of those or it wont help.) While the weather is favourable to powdery mildew you may have to keep spraying but it isn't too much hassle and the small amount of milk in it means it won't smell too bad.

2. Pollination Issues

Plants need to be pollinated to produce the good bits, the yummy bits, the foodie bits. The tassles from corn need to meet with the silks to make heads of corn. The eggplant and tomato flowers need to be shaken at just the right speed and at just the right time to mingle the male and female bits. For cucumbers and zucchinis you need to introduce Mr male flower to the bits of Mrs female flower (she is the one with the baby zuke or cuke attached) for anything to happen. Wet weather isn't good for this. Corn particularly wont set well in the rain. But what to do besides a backwards rain dance? The best policy is just to keep trying. Hand pollinate again and again. Perhaps save some of the bits like the corn tassles or the male flowers of cucurbits in the fridge overnight and then see if the weather has improved thus hand pollinate the next day. Rain doesn't completely stop pollination from happening, it just gets in the way. So when wet weather sets in practice some hand pollination and time it well, otherwise you mightn't get much from your balcony crops.

3. Drainage.

Drainage, good drainage that is, has to come from the very beginning. It can be rectified later on if needs be but it is tricky and some plants wont survive the move. My advice is make sure you have the right pot for the right thing, and make sure it is big enough. If it isn't a self watering pot make sure to include plenty of drainage holes. If these holes are only on the bottom then make sure the pot is up away from the ground or off a surface otherwise they get closed over. Make sure you have enough holes, but don't go overboard otherwise you will lose too much water. Plates underneath the pot are a great way to collect water but it is best to raise your pot off them again as otherwise it could lead to drainage issues.

The plant below, my lime tree, doesn't drain that well and at times the new growth will wilt when there is too much water (and indeed when there is too much sun but that is a whole different matter.) See how the supple green limbs are hanging loose in the picture below. That shows poor drainage.

In the bottom of your pots add things like stones or foam or something to add pockets for drainage. I prefer the latter as it is cheap, light and effective.

In this weather, for balconies, make sure your drainage pipes are clear of debris. Dirt, leaves and other bits a pieces can accumulate in them and black them making your balcony a virtual swimming pool and dooming your plants.

Overall these problems are seasonal, and not always a summer issue. But with the world's weather wildly changing it is good to know what to do in these times. Do you have any other issues that come with the wet weather? Any other solutions to the problems listed here?

Genetic control of fruit stripes in tomato

Over the last few years we’ve made many dozen crosses between various striped types and the best tasting heirlooms.  Most of the striped parents were from Brad Gates at Wild Boar Farms, but there were others too.  In studying the F1 and F2 progeny from these crosses, reading what is in the literature, and listening to the experience of a couple respected colleagues – here’s what we’ve learned about genetic control of stripes in tomatoes.

We believe there are at least three different patterns for fruit striping in tomato, all under different genetic control.  All three result in tomatoes that are striking in appearance, and since there seems to be no relationship between fruit stripes and taste or horticultural traits, a tomato can be both great looking and great tasting.

homozygous gs in unripe fruit

According to the Tomato Genetic Resources Center (TGRC) the green stripe (gs) gene causes "irregular longitudinal green stripes in the epidermis of unripe fruit; retaininng chlorophyll for longer period during ripening, and eventually assuming paler color in fully ripe fruit; changes limited to the epidermis".  Generally the color of the stripes in mature fruit is green in fruit with the gf trait (purple, brown and GWR flesh types with retained chorophyll)) and yellow in non-gf types (e.g. red and yellow).  There are exceptions.  The pattern and boldness of the stripes can vary widely.  Casady's Folly shows bold lightning bolt-like stripes.  Others appear to be washed with a gold or metallic green paint (conditioned by gs), with the underlying fruit color appearing as stripes (see photos below). Although the gene is generally considered to be recessive, the gs/+ heterozygote may show faint striping - but not always.  Clearly there are one or more genes interacting with gs which provide for the rich diversity of striping color and patterns.  We know now for example that in anthocyanin fruit (Aft) types the anthocyanin pigment accumulates preferentially in the green stripes - evident in both green unripe and ripe fruit.  Some examples of the diversity are shown in photos below.

gs - yellow stripes on red

gs = green stripes on brown

F2 segregates

Heterozygous gs - faint striping

Casady's Folly

Aft/gs combo

Red - dipped in gold

Red - dipped in green

Fs drawing (from Keith Mueller)

The fruit stripe gene (Fs) causes dark green radial stripes opposite the fruit locules.  These radial stripes tend to fade as the fruit matures.  I have only seen radial stripes on ripe fruit on green flesh (gf) types, for example Indian Stripe or Arbuznyi.  An exception to this may be with Aft fruit, where again anthocyanin appears to preferentially accumulate in the stripes (e.g. Siberian Tiger and Bengal Tiger).  I’ve only seen this one example on a red/orange Aft fruit, so there’s more to learn here.  Expression of the Fs trait is highly dependent on environment - a real frustration when it comes to breeding for these striking radial stripe patterns.

Prominent Fs on ripe purple fruit

Fs in apricot background, unripe fruit (Keith Mueller)

Siberian Tiger - Aft/Fs

Bengal Tiger

We believe there is a third unrelated striping pattern that is evident in some bi-color types.  These broad (often red or orange) stripes radiate in a regular pattern from the blossom end, and I’ve only seed this in orange/red/yellow or green/red bi/tri-color type fruit.  Unlike gs and Fs, these stripes are not evident on unripe fruit.  The color comes from below, rather than in the epidermis.  I think the Wild Boar Farms varieties Beauty King, Beauty Queen and Berkeley Tie Dye (BTD) are examples of bicolor types that may have both gs and radial bicolor striping (note: Gates says Beauty King was derived from a cross between the bicolor Big Rainbow and Green Zebra).  I have not been able to find much in the literature on heritability of the bicolor trait in general or of this unique radial striping pattern – but based on F2 progeny from crosses with BTD and BK there is likely more than one gene involved, and the traits tend to both be recessive.  This summer we’ll have several unrelated breeding lines segregating for this pattern of fruit coloration – so more to come later.

Yellow/Orange bicolor w/ radial stripes

Butt end of BTD type bicolor

Cross section of BTD type bicolor

The interaction between these three independent traits, each resulting in a unique pattern of stripes on tomato fruit, and the effect of interactions with other genes (e.g. gf and y) on these traits make for a wide variety of striped phenotypes, and complicated genetics.   Over the next few years it will be fun sorting out segregating progeny from crosses we’ve made between parents expressing these various genes.

2011 crosses