Section 13 — Plant Genetics and Breeding 



resistance to the mosaic disease. F3 seeds of the 

 selected plants within a line were bulked. 



Evaluation of resistance in the late segregating 

 generations was made by counting the number 

 of mosaic infected plants one month after trans- 

 planting and thereafter counting of mosaic 

 infected plants was made every week until 

 harvesting of leaves. 



For a single entry, selection for mosaic resis- 

 tance and other desirable characters from genera- 

 tion to generation was performed following the 

 bulk method, assuming that continuous selling 

 leads to homozygosis. 



Experimental Results. The Fi hybrids of the 

 reciprocal crosses were identical and were 

 intermediate in most characteristics between the 

 parents, especially with respect to height, 

 position and shape of leaves. 



In all cases the majority of the Fi plants were 

 very susceptible to the mosaic disease under 

 artificial inoculation indicating that recessive 

 factors control mosaic resistance. Selected mosaic 

 resistant F2 plants, assuming that one pair of 

 factors controls resistance should have produced 

 all resistant plants in the succeeding generations, 

 but the fact that they did not, like the resistant 

 parent, suggests that resistance is controlled by 

 multiple recessive factors. 



The segregating hybrids showed significant 

 difference in their degree of resistance in all 

 four years of testing. The hybrid lines Amsim 

 (Ambalema ■ Simmaba) and Simam (Simmaba 

 x Ambalema) were the most resistant followed 

 by Maram type B (Marogui x Ambalema); 

 Amar type A (Ambalema x Marogui) and Vi- 

 zam type A and B (Viscava x Ambalema). 



Generally, hybrid lines were significantly 

 more resistant than the susceptible parents, 

 and as resistant as the introduced parents. 



13.91. Method of Crossing Geographically Remote 

 Forms in Winter Wheat Breeding. P. P. Luky- 



ANENKO (U.S.S.R.). 



graphically remote forms of soft wheat supple- 

 mented with repeated crosses and controlled 

 individual selection led to the development of the 

 new, for the North Caucasus highly productive 

 winter wheat varietal type: Bezostaya 1 variety 

 (Lutescens). It is one of the first Soviet intensive 

 varieties that is distinguished among all winter 

 wheats for its short stem, lodging-resistance, 

 productive heads, weak susceptability to sriple 

 and brown rust, high yielding ability and good 

 milling and baking quality of grain. 



Wheats of rather remote geographical and 

 ecological origin which belong to varieties 

 cultivated in various countries and continents 

 Argentine, Italy, Japan and others) had 

 become components of the genealogy of Be- 

 zostaya 1 variety. 



Many years of the State Variety Trials showed 

 Bezostaya 1 to be one of the most productive 

 varieties among winter wheats in main winter 

 wheat growing areas of the U.S.S.R. (except 

 regions of severe climate). This variety yields over 

 50-60 centners per hectare. Having unprece- 

 dented yielding ability this wheat variety is 

 characterined by high grain quality and features 

 of "strong" wheats. Bezostaya 1 is the first 

 winter wheat in the Soviet breeding which is 

 widely cultivated not only in the Soviet Union 

 but in some foreign countries (Hungary, Ru- 

 mania, Bulgaria, etc.). 



The report describes in brief the adopted 

 method of breeding; the initial breeding stock; 

 correlation coefficient that determines the main 

 trends of breeding; the method of individual 

 selections in hybrid populations and particularly 

 selection for brown rust resistance. The report 

 touches on a problem of the further rise in wheat 

 productiveness in humid areas by means of 

 developing varieties with still lower stems and 

 highly productive heads. These varieties have a 

 complex of biological characters on which their 

 adaptability to local conditions depends. The 

 report presents a brief survey of obtained 

 material and perspectives of winter wheat 

 breeding for high productiveness. 



The lasting use of the method of crossing 

 geographically remote forms which had been 

 first suggested by I.V. Michurin proved highly 

 efficient in winter wheat breeding at the Krasno- 

 dar Agricultural Institute. In combination with 

 controlled individual selection this method 

 permitted to create regularly new varieties with 

 the complex of necessary economic and biological 

 characters and to raise the upper limit of the yield 

 of the developed varieties. As a result the yielding 

 ability of varieties doubled and during a short 

 period rose from 21.1 up to 50.6 centners per ha. 



Interspecific hybridization of selected geo- 



13.92. A Homozygous Heterozygote. Benjamin 

 H. Beard (Brawley, U.S.A.). 



After all recombinations have been achieved, 

 varietal improvement by plant breeding methods 

 would appear impossible. Generally speaking 

 additional chromatin indicates an evolutionary 

 advance, i.e. as the chromosome number 

 increases the organism becomes more compli- 

 cated. Drastic changes such as the addition of 

 one or more chromosomes probably require 



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