THE SWEDISH GENETIC INSTITUTE IN AKARP 107 



work, now about thirty years old, involving numerous crossings, combinations and 

 selections, has been necessary. At the moment an increase in the mean yielding* 

 power of about 40 % has been reached in South Sweden (through the raising of 

 the new cross*variety Pansar* or Ironwheat, and others); in the more severe clU 

 mate of middle Sweden about 20 % has been reached (through Thule II and others). 



The writer continues his former work along this line hoping to be able to 

 add the remaining part of the calculated increase to the present yielding*power of 

 the wheats in South Sweden; continued crossings in large measure are therefore 

 made and worked out (for example between Pansar and the very high yielding 

 Dutch variety Vilhelmina, not winterhardy in Sweden). Furthermore, the breeding 

 work aims at reaching the greatest possible straw stiffness, resistance against disea* 

 ses, improved quality of grain etc. An extensive breeding work in these direc* 

 tions has still to be carried out in the winter wheats. 



A similar extensive breeding work with summer wheat is also going on at 

 the institute. The early ripening plays here, contrary to the winter wheats, a very 

 important role. High yielding varieties of middle Europe give in Sweden, espe* 

 cially in cold summers, only a low yield. This is due to the fact that they ripen 

 too late, so that the grain does not reach its definitive, ordinary size. The main 

 point here is therefore to combine to so high a degree as possible highyielding 

 power and early ripening. The work already carried out in Svalof by the writer 

 shows that this combination is possible to a much larger degree than one would 

 think for purely physiological reasons. A new variety has been raised, which now 

 is grown extensively in South Sweden. This variety combines the time of ripe* 

 ning characteristic of the ordinary Swedish summer wheat, formerly cultivated 

 extensively, with 1215 % higher yielding power (as seen from the official re* 

 ports on sortstrials during a series of years). If it is possible through continued 

 crossing=work to reach an increase in the yielding*power of 30 % the growing of 

 summer wheat in the rich soils of South Sweden, where it is now grown only on 

 a very small scale, would undoubtedly largely increase, provided that the time of 

 ripening remains the same. This breeding work embraces also crossings between 

 summer wheats and the best and highest yielders among the winter wheats, a pro* 

 mising piece of work, although very difficult as the segregation of many characters 

 here is very complex, and because of the appearance of numerous bad transgressions. 



Crossings between winter and summer rye, with the object of improving the 

 latter one, are also carried out and followed. 



A special point of study in the plant breeding work carried out at the insti- 

 tute is to record new hereditary differences of value to the breeding, and to study 

 their genetical construction. In barley, for example, the writer has discovered 

 that certain varieties are quite immune against the attacks of the nematode Hete- 

 rodera Schachti, while most of the other varieties, including the highest yielders, 

 are susceptible (Hereditas I, 1920). Much work has therefore to be done in or* 

 der to combine high yielding*power and other desirable qualities with immunity. 

 This is of importance not only with regard to the barley breeding itself, but also 

 and still more with regard to other cereals as oats and wheat, where no such 

 hereditary differences are met with, all varieties being equally susceptible. When 

 during the rotation of the crops immune varieties of barley are grown, which do 



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