Re: how would you form a seedless strawberry?

Grafting alone cannot give rise to a seedless fruit plant. Grafting can only be 
used to propagate woody seedless plants once one is found or made. Strawberry 
is propagated by runners, which is much easier then grafting. 

Seedless fruit plants have arisen by mutation, such as the naval orange and 
banana; by breeding as for seedless watermelon and seedless grapes; in some 
dioecious species, such as persimmon, when no male plants are nearby; and in 
some species which cannot self-pollinate, such as pineapple. Application of 
plant hormones (auxins, gibberellins or cytokinins) often can give rise to 
seedless fruits. Home gardeners can get seedless tomatoes by applying a special 
product containing an auxin to the flowers. 

There is a classic experiment with a developing strawberry fruit often shown in 
botany textbooks (Moore and Clark, 1995) in which all the seeds are removed 
from the outside of a developing strawberry fruit. With the seeds removed, the 
fruit stops developing. However, if auxin is applied to the deseeded fruit, it 
will develop nearly normally. 

If you wanted a seedless strawberry, the hormone approach would probably be the 
most direct, if it would work. You would have to prevent pollination of the 
flowers, which leads to seeds, by caging the plants with insect proof screen. 
Then you would apply auxin to the flowers. A strawberry fruit is an accessory 
fruit because much of the edible part of the fruit is formed from the flower 
receptacle. The real fruits (achenes) are what is commonly termed the seeds.

Ultimately, it would not be worthwhile economically to produce seedless 
strawberries because the strawberry seeds are so small and easily eaten. 
Seedless fruits are economically important when the seeds are not easy to chew 
and digest, as they are in grapes, citrus, bananas and pineapples.  

References

Moore, R. and Clark, W.D. 1995. Botany: Plant Form and Function. Dubuque, IA: 
Wm. C. Brown.


Strawberry Auxin Experiment