Mav, 1921. 



SCIENTIFIC AGRICULTURE 



W6 



Earliness in Wheat and its Inheritance 



I'.y \V. P. THOMl'SOX. 

 Professor of Biology, University of Saskatchewan, Saskatoon. 



In previous papers (3, 4) tlie writer has given the re- 

 sults of studies en the inheritance of the length of the 

 period from i)laiiting to ripening in wheat. The date 

 covered the first tliree hybrid generations of several 

 crosses. In the present paper data will he given on the 

 later generations of these crosses as well as on several 

 additional ones and the results as a whole will be cor- 

 )-c]ated and interpi'cted. 



In many parts of tiie world and i)articularly in West- 

 ern Canada a necessary or higldy desirable "juality of 

 crop plants is rapidity in maturing. The early plant 

 escapes the danger from frost where the season is short. 

 'It has also been slu)wn that it e.scapes damage from rust 

 toa much greater extent tluui do later varieties. More- 

 over earlier varieties would extend the area of safe 

 farming much further north. In Australia and India 

 quickly ripening varieties are necessai-y l)ecause of the 

 shortness of the wet season. 



The i^roduction of (piickly maturing varieties through 

 lilant-breeding operations should be facilitated by a de- 

 termination of the mode of inheritance of earliness and 

 lateness. The number of hereditary factors involved, 

 the number of offspring which must be raised in order 

 to recover the parental conditions if this be possible, the 

 correlations between earliness and other qualities, part- 

 icularly undesirable ones, will veiy largely affect the 

 success of the practical measures and will determine the 

 most advantageous way in wliicli to carrv them on. 



DR. W. p. THOMPSON. 



Moreover it appears that the conditicns in wheat as des- 

 cribed in the following pages are probably similar to 

 those in other plants .so far as one can judge from the 

 limited information available f(u- other plants. If that 

 l)e true the conclusions reached may form a basis for 

 work on many different cro() ))lants. 



Early Varieties. 



In order to make a comprehensive study of the prob- 

 lem a systematic endeavor lias been made to secure as 

 many as possible of the earliest varieties now grown, 

 particularly as it seemed tliat different varieties might 

 owe their earliness to different factors which could be 

 recombined. Hundreds of varieties have been secured 

 and tested from many countries including United States, 

 Australia, India, China, Japan, Siberia. Alaska, Asia 

 Minor, Persia, Mesopotamia, and many European coun- 

 tries. In Table I. a list of varieties is sriven -which have 



proved earliest in this locality over a .series of year:;. 

 Owing. to the variations in the length of the peri'rd in 

 different years the rcckfinings have been made from the 

 earliest variety as zero. The figures give the average of 

 several years" results, usually five. No varieties later 

 than Marquis have been included except Red Fife and 

 Hed Bobs wliich have a special interest in Western Can- 

 ada. All these results were obtained with juue line se- 

 lections. In many cases notably Calcutta. Sonora, Fe- 

 deration and Red Bobs, it was found that the original 

 samples showed cciisiderable variation in regard to earli- 

 ness, and gave rise to pure lines with different mean 

 conditions. 



No claim is made concerning the completeness of the 



list. It contains most of those that could be secured 



through the efforts of many friends and correspondents. 



Very probably a systematic exploration jiarticularly in 



Australia, India and Siberia would reveal manv others 



and perhaps some still earlier. 



TABLE I. 



,. . . „ Number of 



variety Source Species days later than 



the earliest 



