A NEW METHOD OF SELF-POLLINATING 



CORN 



INFerlr T. Jenkins, 

 U. S. Drpartiiioit of A(/ricultiire, IWisJiiiujtoii, I). C. 



EXTENSIVE cooperative corn 

 breeding experiments were inau- 

 gurated at Ames. Iowa, in 1922. 

 by the Office of Cereal Investigations, 

 U. S. Department of Agriculture, and 

 the Iowa Agricultural Experiment Sta- 

 tion. It was necessary to make a large 

 number of self-pollinations in connec- 

 tion with these investigations, and a 

 modified technique has been developed 

 that is efficient both as to time and re- 

 sults. Because of the interest in se- 

 lection within selfed lines as a means 

 of corn improvement and the large 

 number of selfs that are being made 

 each year, it seems desirable to pre- 

 sent the modification at this time. 



A method of hand-pollinating used 

 in the Office of Cereal Investigations 

 for some years has been as follows : 

 The ear-shoots are bagged before any 

 silks have appeared. After a few silks 

 emerge, the shoot is cut back ^ to 

 13^ inches and the bag is replaced. In 

 from twenty-four to forty-eight hours 

 a good brush of silks some two inches 

 long is ready to pollinate. The method 

 of bagging and cutting back shoots 

 is illustrated in Figure 17. The 

 tassel required for any pollination may 

 be bagged at the time of cutting back 

 the given shoot. From twenty- four 

 to forty-eight hours' protection from 

 stray pollen is thus given, during which 

 time any foreign pollen that previously 

 had lodged upon the tassel may lose its 

 viability. 



Bags of glassine paper two and one- 

 half inches wide and six inches long 

 have been found convenient for bagging 

 the shoots before pollination. As they 

 are semi-transparent, the development 

 of the silks may be watched and the 

 time otherwise required to feel each 



shoot is saved. The size of the bags 

 is such as to give sufficient room and 

 yet to stay in place without fastening. 

 Occasionally a bag is lost, but a little 

 practice in using them reduces this loss 

 to a minimum. Heavy twelve-pound 

 paper bags have been used for the tas- 

 sels in selfing and the same bag is used 

 to protect the shoot after pollination. 



The method used in 1922 was similar 

 to this up to the time of cutting back 

 the shoots. At this time the tassel was 

 pulled, shaken to free it from foreign 

 pollen, and enclosed with the shoot in 

 a twelve-pound bag. In order to keep 

 the tassel shedding, its stem was in- 

 serted into a small bottle of water that 

 had been attached to the stalk. 



It was found desirable to have two 

 men operate together. One carries tags 

 for labeling the ears and a pail of water 

 containing a supply of small, wide- 

 mouthed bottles. Operating from the 

 side of the plant bearing the ear-shoot 

 he first fastens a tag just above the 

 ear-bearing node, and then fastens one 

 of the small bottles of water to the 

 stalk just above the tag. The tag 

 should be to his right and the bottle 

 to his left as he faces the plant. 



The other man carries a supply 

 of twelve-pound paper bags, paper 

 clips or string, and a knife. Oper- 

 ating from the opposite side of 

 the plant, he pulls the tassel, frees it 

 from pollen by shaking, and puts it 

 into one of the bags. He then removes 

 the glassine bag, cuts back the shoot, 

 and places the bag containing the tassel 

 over the shoot, inserting the stem of 

 the tassel into the bottle of water. The 

 stem should be kept to the back of the 

 bag (away from the stalk) and to the 

 rioht for convenience in handling. 



41 



