Section 13 — Plant Genetics and Breeding 



plants under cold chamber temperature — 12°C 

 for 30 hr. 



By crossing steppe-like varieties with medite- 

 ranean (mainly Italian) varieties we got the hy- 

 brids with 5.0-93.3 per cent of cold resistance. 

 Among Italian varieties San Pastore showed the 

 highest effect on frost hardiness. The hybrids 

 from this variety had 53.3-93.3 per cent survived 

 plants. The cultivars like Produttore, Leonardo 

 and Mara have lower frost resistance. Espe- 

 cially the cultivar Mara demonstrated a high 

 grade of susceptibility to frost. 



Italian varieties intercrossed gave the Fi hy- 

 brids with 1.6-5.0 per cent of alive plants. 



F2 hybrids were tested under — 14, — 16 and 

 — 18°C in the course of 16 hr and showed dif- 

 ferent reactions up to the severeness of test. By 

 — 14°CF2 progenies were intermediate between 

 their parents. The last two temperatures resulted 

 in high winter killing. 



From hardier parents came more frost- 

 resistant plants in F3 generation. Some F3 

 progenies combined the spring character with 

 good winter hardiness. 



Breeding wheats with still greater hardiness 

 is being continued and it is expected to pro- 

 duce high yielding material with satisfactory 

 frost resistance. 



1 3.55. The Transforming of Winter Italian Wheats 

 With Low Cold-resistance into Spring Wheats 

 in Moscow Region. R. D. Glavinich (Moscow, 

 U.S.S.R.). 



In the course of 1958-1962 an experiment was 

 carried out on changing the heredity of soft 

 Italian wheats with low cold-resistance (30 

 varieties) which are characterized by their 

 non lodging and with high agrotechnics give 

 40-45c on 1 hec.^ 1 ) 



The work has been carried out in two direc- 

 tions: (1) to obtain winter wheats with high cold- 

 resistance for Moscow region and (2) to obtain 

 spring forms out of the same initial material. 



We have used the following method of chang- 

 ing Italian wheats with low cold-resistance into 

 wheats with high cold-resistance. By twofold 

 autumn sowing (18-20 October) under the in- 

 fluence of spring-summer conditions we have 

 changed winter forms with low cold-resistance 

 into spring forms. Then by optimal sowing 

 (25-31 August) we have transformed them into 

 winter forms with high cold-resistance. By 

 this method we have changed 16 varieties out 

 of 30, but only 6 of them have become real win- 

 ter forms for Moscow region (80-100 per cent 

 of their F3 survived winter of 1961-62). 



The vegetative period of new winter forms 

 in F3 did not differ from the standard winter 

 varieties and in two forms was 4-7 days shorter. 

 The absolute weight of 1000 grains of new winter 

 wheats was more than 40 g, the weight of the 

 standard being 38-39g. The yield of these forms 

 averaged 44c on 1 hec, the yield of the standard 

 being 36-37c on 1 hec. All six winter forms were 

 morphologically alike. Three of them (Kva- 

 derna, Forlani and Klavatino) are the per- 

 spective forms for the Moscow region. 



After three years of spring sowing (1959-1961) 

 9 real spring forms have been chosen out of 30. 

 88-98 per cent of them ripened in 1961 (spring 

 standard variety Moscowka). The vegetative pe- 

 riod of new spring forms was 2-5 days shorter 

 than that of the standard. The absolute weight 

 of 1000 grains was 1-4 g bigger than that of the 

 standard. Some of the new spring forms (For- 

 tunato, 1373, Forlani) are of interest for selec- 

 tion. 



1. 1 centner (c) 

 10.000 m 2 . 



50 kg. 1 hectare (hec) = 



13.56. Molecular Structure of DDT Analogues in 

 Relation to Gene Action in Barley. G. A. 



Wiebe (Beltsville, U.S.A.). 



The insecticide DDT kills certain barley 

 varieties and not others following foliar applica- 

 tions of this chemical during the seedling stage. 

 Inheritance studies show this reaction is con- 

 trolled by a single gene and that resistance is a 

 recessive character. Biochemical tests show that 

 DDT enters the leaf tissue of resistant and sus- 

 ceptible plants in approximately equal amounts. 

 Since the reaction appears to be highly specific, 

 tests were undertaken to determine the reaction 

 of a series of DDT analogs to this gene. On the 

 basis of incomplete tests of a group of 50 analogs, 

 8 were found that reacted similarly to DDT. 

 In comparing the chemical composition and 

 structure of those analogs that gave a differential 

 kill with those that did not, one finds that the 

 structure of the molecule is of greater impor- 

 tance than its composition. This finding is in 

 line with the growing concept in molecular 

 genetics that the specificity of gene action may 

 be governed in part by the secondary and ter- 

 tiary structure of its primary product, an en- 

 zyme. For example, in the present case, where 

 ordinary p,p' DDT will kill one variety of 

 barley and not the other, the o,p' DDT form 

 will kill neither variety. The specific action of 

 DDT on barley has not been determined. It 



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