PROBLEM 5. Breeding New Types of Animals and Plants 



501 



Fig. 452 These blueberries 

 are a little over one inch 

 across but they lack flavor. 

 This plant has been hybrid- 

 ized with a plant known for 

 its flavor. Selectio7i was 

 practiced. One bush was ob- 

 tained whose berries com- 

 bined large size and flavor. 

 What step is necessary be- 

 fore such a plant can be said 

 to be a successful variety? 



(U. S. DEPARTMENT OF AGRI- 

 CULTURE) 



ancestors. After the first crosses were 

 made a reasonably pure breed was estab- 

 lished through careful selection and in- 

 breeding. You can see that this is not hap- 

 hazard hybridization; the breeder delib- 

 erately selects two parents each of which 

 has a desirable character which the other 

 lacks. If he is successful, an organism is 

 produced with a combination of the de- 

 sired traits. The breeder has made a new 

 type to order. Crosses between our native 

 beef cattle and cattle from South Africa 

 promise even greater success. Try Exer- 

 cise 6. 



Crosses between diff^erent species 

 rather than between different varieties, 

 have also been attempted. Of course, hy- 

 bridization between the horse and 

 donkey is not new. The highly desirable 

 mule results. But the mule, with rare ex- 

 ceptions, is sterile (cannot reproduce). 

 We now have crossed the bison (buffalo) 

 with domestic cattle and produced the 

 cattalo. Sometime this new kind of ani- 

 mal may become commercially valuable. 



There are many interesting reports for 

 you to make to your class. See Exercises 

 7 and 8. 



Hybridization in plants. Dutch scien- 

 tists in Java decided to make a new sugar 

 cane to order — one that combined the 

 good qualities of two different varieties. 

 The sugar cane that grows wild in Java 

 contains almost no sugar but it is highly 

 resistant to disease and to insect enemies. 

 The cultivated cane is rich in sugar but 

 is particularly susceptible to disease. Hy- 

 bridizing put together into one plant the 

 desirable combination of genes which 

 had never existed together before. In 

 three years the new variety was estab- 

 lished. In plant hybridization it is easier 

 as a rule to "fix the type" than in animal 

 work. Can you foresee the reason.' You 

 will read about it later. 



The United States Department of Ag- 

 riculture has sent biologists to other for- 

 eign lands: to Manchuria and Mongolia 

 to search for drought-resistant, soil-bind- 

 ing plants; to Russia for wheat that is 



