Section 13 — Plant Genetics and Breeding 



13.45. Percent Dry Matter as an Index for the 

 Evaluation of Individual Plants and Strains of 

 Sugar Beets (Beta vulgaris L.). P. Bergen 

 (Tober, Canada). 



Data will be presented which indicate that 

 percent dry matter of the petiole is under the 

 control of a genetic mechanism which also 

 influences the sucrose content of the root. 

 Percent dry matter of the petiole is positively 

 correlated with sucrose percentage in the root 

 and negatively correlated with root weight. The 

 progeny of plants selected for percent dry matter 

 of the petiole showed that significant changes 

 had been obtained for percent dry matter of the 

 petiole, percent sucrose, percent dry matter of the 

 root, root weight and sucrose yield. A further 

 experiment demonstrated that percent dry 

 matter of the leaves and petioles of young sugar 

 beet plants may be used to predict the potential 

 root yield and percent sucrose of sugar beet 

 varieties and strains. 



13.46. International Sources of Resistance of Wheat 

 Tested in Respect to the Major Physiologic 

 Races of Puccinia recondita Rob. ex Desm. in 

 Yugoslavia. Momcilo Boskovic (Novi Sad, 

 Yugoslavia). 



In order to select the best sources of resistance 

 to the prevalent physiologic races of Puccinia 

 recondita in Yugoslavia, i.e. 6, 20 and 77, as well 

 as some races of minor importance, such as 17 

 and 105, a large number of varieties and hybrids 

 of wheat was tested for resistance in the green- 

 house at the seedling stage of plants to the various 

 races, and in field tests at the adult stage of 

 plants. These experiments were conducted in the 

 years 1960, 1961 and 1962. 



It has been observed that the races used 

 segregate many of the wheat varieties and hybrids 

 with a greater or lesser degree of resistance into 

 resistant variants of plants on the one hand and 

 susceptible ones on the other. 



From international winter wheat rust nurseries 

 six hybrids with the highest resistance were 

 selected, in which segregation occurs only in 

 respect to one race in the greenhouse. A still 

 higher degree of resistance to all the races 

 examined, and that without segregation, was 

 found in Chinese X Ae.umbelhdata P-54-44-16 

 and B.Y., selected from international spring 

 wheat rust nurseries. Apart from the above 

 varieties and hybrids, some other valuable 

 material, selected on the basis of the present 

 investigation, has been presented in this paper 

 in the tables. The best hybrids selected are 



intended for use as sources of resistance in our 

 breeding programmes. 



It has been found that many sources of 

 resistance used in various countries show either 

 complete susceptibility or only partial resistance 

 when used in Yugoslavia, while only a small 

 number of these is fully resistant to our races of 

 the parasite. 



13.47. Seedling Reaction to Leaf Rust Races of 

 Wichita Wheat Lines with Genes for Resistance 

 Transferred from the Differential Varieties. 

 E. G. Heyne and C. O. Johnston (Manhattan, 

 U.S.A.). 



A series of lines of Wichita hard red winter 

 wheat has been developed for separating 

 physiologic races of Puccinia recondita Rob. ex 

 Desm. These lines have been obtained by trans- 

 ferring the genes for resistance from the eight 

 standard differential varieties. Wichita was the 

 recurrent parent and the backcross lines available 

 for study have reached the 4th to 6th backcross. 

 The resistance of Transfer, which has leaf rust 

 resistance derived from Aegilops umbellulata, 

 also has been transferred to Wichita. Tests with 

 physiologic races from eight important race 

 groups have shown that the backcross Wichita 

 derived lines have a similar reaction to the 

 standard differentials. The Wichita line with the 

 Hussar reaction gives readings more like those 

 originally described. Apparently the Wichita 

 background results in less variation to leaf rust 

 infection than when the factor for resistance is in 

 Hussar. These Wichita backcross lines have an 

 advantage in that they all have the same growth 

 habit and virtually are the same except for 

 reaction to various leaf rust races. In the present 

 material apparently only one major gene from 

 each donor parent has been transferred. For 

 example, the Wichita 5 x Carina and Wichita 5 x 

 Brevit do not have the resistance of Carina or 

 Brevit to race 9 of leaf rust. Seed of these Wichita 

 backcross lines are available for use by other 

 investigators. 



13.48. Inheritance of Rust Resistance in Stem Rust 

 Differential Varieties of Wheat. W Norman 

 D. Williams and F. J. Gough (Fargo, 

 U.S.A.). 



The inheritance of seedling resistance to 

 physiologic race 1 1 1 of Puccinia graminis f. sp. 

 tritici Eriks. & Henn. was studied in eight of the 

 stem rust differential varieties of wheat. Physio- 



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