JOlfflSL OF AGRKIIIIRAL RESEARCH 



DEPARTMENT OF AGRICULTURE 

 Vol. VI Washington, D. C, June 19, 191 6 No. 12 



CORRELATED CHARACTERS IN MAIZE BREEDING 



By G. N. CoLUNS, 

 Botanist, Office of Acclimatization and Adaptation of Crop Plants, Bureau of Plant 



Industry 



INTRODUeXION 



The study of correlations as an aid to plant breeding was at one time 

 thought to be full of promise, but in recent years little use has been made 

 of correlations by practical workers. From this fact it might appear 

 that the early hopes were unwarranted, and that correlation is a factor 

 of little or no importance. It must be conceded that the elaborate 

 calculations of correlation coefficients have in few instances proved of 

 value to the practical breeder, yet it must be admitted on reflection that 

 nearly all successful breeding has in reality been made possible by the 

 fact that correlations exist. 



In plant breeding the improvement and preservation of varieties has 

 largely resulted from the ability of the breeder to recognize desirable 

 types, and the existence of definite types is in itself a manifestation of the 

 correlation of characters. The existence of types must mean that there 

 are many individuals that present approximately the same combination 

 of characters, and this is exactly what correlation implies. The charac- 

 teristics of the desired type are recognized by the breeder even though they 

 may not be formulated, and varieties are seldom established by selection 

 confined to a single character. If the study of correlations has appeared 

 to have little bearing on plant breeding, it must be that we have been 

 studying the wrong characters or studying them in the wrong way. 



In the improvement of maize varieties (Zea mays), as with other plants, 

 the recognition of types has been an important factor. The selection, 

 however, has been almost entirely confined to the ear. In a field of any 

 commercial variety it is easy to recognize differences in the plants, but 

 even after long familiarity with the variety the plants refuse to be classi- 

 fied into distinct groups. This difficulty in recognizing types among 

 maize plants greatly increases the difficulty of breeding this crop. 



The lack of recognizable types in maize is very different from the con- 

 dition that obtains, for example, in cotton (Gossypium spp) . With cotton. 



Journal of Agricultural Research, Vol. VI, No. la 



Dept. of Agriculture, Washington, D. C. June 19, 1916 



ee Cr— 84 



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