Aug. 2, 1920.] Agricultural Gazette of N.S.W. 549 



Improvement of Sweet Sorghums^ 



E. BREAKVVELL, B.A., B.Sc, Agrostologist. 



Sweet sorghum may be considered an extremely variable species of plant. 

 There appears no doubt that all our cultivated varieties (including Sudan 

 grass) originated in Africa, and as there is a considerable diversity between 

 the wild and cultivated forms as found in that continent, little wonder can 

 be expressed at the numerous types grown in other countries. In the 

 United States more types are grown than in this State. Commercial seed 

 houses there catalogue types called Sumac, Red Amber, Dakota Amber, 

 Minnesota Amber, Honey, and Collier. 



These are very distinct types, not only in the habit of the plants, but 

 also in the colour and shape of the seed. In this State the principal 

 commercial types are Planter's Friend and Iraphee (both derived from the 

 South African Imphee types). Amber Cane, Sorghum saccharatum, and 

 (more recently) Saccaline. These are also very distinct in habit of growth, 

 and shape and colour of seed. 



The sorghum flower is particularly adapted to wind pollination, and 

 crossing between types grown close together and maturing at practically 

 the same period is sure to happen. Crossing very readily takes place with 

 broom millet, but owing to the very pithy nature of that plant the seed 

 from such crosses is worthless. A broom millet x sweet sorghum plant 

 is quite as pithy as the original broom millet parent. It is a veiy important 

 matter, therefore, that farmers should obtain seed as true to type as possible. 

 At the present time crops of sorghum with a distinct lack of uniformity and 

 containing two or more types, are quite common. 



How Improvement is Effected. 



In addition to the natural cross-pollination of different strains of 

 sorghums, crossing also takes place between plants of the same strain. 

 If an ordifiary crop of Planter's Friend be examined, for example, 

 certain individual plants will be found to be marked by exceptional vigour 

 and other desirable characters. Such plants are called by scientists 

 " heterozygotes," and the exceptional vigour, etc., are due to the com- 

 bination, or segregation, of certain factors, or "units." If the seed of the 

 individual heads of such plants be sown the following season m such a way 

 that each row represents the progeny of one certain parent plant, there 

 will be a considerable diversity in the plants, some being very good, 

 others medium, and others very poor. The result is quite in accord with 

 Mendelian principles, for in the parent plant — that is, the first generation 

 of the cross — certain undesirable characteristics, known as rece.ssives, were 

 suppressed, and these reappear in the second generation. The best plants 



