Friday, April 4, 2014

Plant Breeding for the Home Gardener by Joseph Tychonievich

For those of you who would really not want to learn all the fine details of why vegetable breeding works or would just rather not read a really long book about vegetable breeding Plant Breeding for the HomeGardener by Joseph Tychonievich is just for you.

This book is great for those who do not want long reads.

One of the first things that I look for in a plant breeding book is if the author includes specific factors to select vegetables for when seed saving. In one chapter,  Tychonievich discusses selective traits for vegetables such as beans, cabbage, corn, lettuce, squash and tomatoes. The trait that most interested me in this chapter has to do with tomatoes. Tomato acidity and sweetness are noted as a few traits, along with an interesting trait known as umami. Umami, a meaty glutamate that tomatoes produce, is one of the things that make them so popular. I wonder if there is any simple method by which a gardener can test umami like you can test acidity and sweetness?

Though PlantBreeding for the Home Gardener is fun and easy to read,  it also contains some more advanced techniques and thoughts that are worth learning more about. In the chapter entitled “Beyond the Backyard – Advanced Techniques” Tychonievich references ideas such as polyploidy and embryo rescue.

Polyploidy refers to the genetic makeup of a specific plant. A diploid has 2 copies of genetic code while a tetraploid has 4 copies of a genetic code. Sometimes crosses between diploids and tetraploids are possible and sometimes they are not. As plants with different genes exhibit different growth patterns and flowering crossing diploids and tetraploids can sometimes result in very interesting (and sometimes more productive) results. However, crossing diploids and tetraploids can sometimes result in triploids, which are often sterile.

My garden is currently growing Jerico lettuce
which was bred for heat-tolerance and not for beauty!

Sometimes when making a cross between two similar species of plants the embryo of the seed aborts, or falls off the plant, before maturing. Gardeners can save the embryo of a difficult cross by a technique referred to as embryo rescue. According to Tychonievich, embryo rescue is “one of the most powerful techniques for getting new hybrids between species”. The method for rescuing an embryo requires the gardener to remove the seed embryo from the plant then place it in a substrate that enables the embryo to grow into a small plant, which can then be grown to seed. The substrate often consists of a gelling agent (such as agar), a small percentage of sucrose (to feed the embryo), specific salts (Murashige & Skoog (ms) basal salt mixture) that can be bought online. Tools and recipes for embryo rescue can be found online.

What interests me most about embryo rescue is not to apply this technology and methods to making new hybrids but in saving the rare seed that we already posses. Sometimes old seed has a very difficult time germinating and once it does germinate the growth of the seedling can be incredibly slow. If the gardener has very little seed and the seed is rare, it may be worth looking into embryo rescue as a means to provide nourishment to the seedling. Later stage embryo rescue techniques could be used with such seed to imbibe increased vigor by feeding weak seedlings until they at least push off their seed coating. In one online source, the research geneticist Sandra Reed notes that later stage embryo development could occur in a simple inorganic medium (agar) supplemented with 2-3% sucrose (powdered sugar).

In summary, Plant Breeding for the Home Gardener has something for everyone. The majority of this book contains ideas that are presented in a very straightforward manner while some of its more advanced concepts provide inspiration for further research and development by the lowly gardener.

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