Friday, April 15, 2011

Breeding New Fruit Varieties

   Besides growing fruit for sale, I'm also conducting an apple breeding program.  (We got some needed rain last evening, and it's in the low 40's this morning, so I have time to post this, after working outside 11 hours a day for the past 3 weeks.)  We grow apple varieties immune to apple scab disease, such as 'Enterprise' and 'GoldRush', so they don't need to be sprayed for apple scab.  This means the scab-immune apples need only half the sprays (7 or 8 per year) that scab-susceptible varieties such as 'Jonathan' or 'Fuji' do (they need 15 or 16 sprays per year).
   These scab-immune apple varieties came from a breeding program that started back in the 1940's.  I'm continuing this work by crossing some of these varieties and numbered selections that haven't been named yet.  This year I made crosses between 'GoldRush' and Coop 27, a numbered selection with fruit that tastes similar to 'Jonathan'.
    To make controlled crosses, I first remove the anthers, petals and sepals from some flower buds on the tree I'm going to cross.  Bees won't visit a flower with no petals, so it won't get pollinated by unknown pollen, and I'll later transfer known pollen I've collected from the variety I want to cross with. Fruit I've pollinated will develop without sepals, so I can tell my crosses from all the other fruit on the tree.
I'm removing the anthers, petals and sepals from a flower bud here.

   I  pick out and dry the anthers I've removed, and use the pollen they contain to pollinate the stigmas on the tree I'm crossing.

   In the fall, I'll look for fruit with no sepals on the trees I crossed, and save those.  I save the seeds, and stratify them by placing them in plastic bags of moist vermiculite in the fridge, to give them a moist, cold treatment so they'll germinate in spring.  In late April I plant the seeds from last year's crosses in small pots, grow them over the summer, then plant in the field in the fall.  Seedling trees take longer to start fruiting than grafted trees, so it'll be 7 or 8 years before I can evaluate fruit, discard trees with inferior fruit or disease susceptibility, and hopefully get a few selections worthy of testing and possibly eventually naming as new varieties.  Crosses I made 9 years ago have just bloomed well this year, so I'll evaluate them this fall.