Among collections chiefly from North China,different races of Pucciniaglumarum were identified by means of differential hosts used by Gassner & Straibor a set of improved varieties of wheat grown in China. Among 14 improved varieties,marked differences in resistance to stripe rustwere observed.Li-Yung I was resistant to 40 out of 50 collections of striperust,with unstable reactions to 7 collections; Nanking 4197 was resistant to 37 ??collections with unstable reactions to 9 collections; while Yechao 35368...

Among collections chiefly from North China,different races of Pucciniaglumarum were identified by means of differential hosts used by Gassner & Straibor a set of improved varieties of wheat grown in China. Among 14 improved varieties,marked differences in resistance to stripe rustwere observed.Li-Yung I was resistant to 40 out of 50 collections of striperust,with unstable reactions to 7 collections; Nanking 4197 was resistant to 37 ??collections with unstable reactions to 9 collections; while Yechao 35368 and Ye-Ta 1885 were susceptible to all except 5 collections from FJymus ckinense.Theinstability of varietal reactions is one of the principal obstacles in identification.As a consequence,tests with 6 improved varieties including Early Premium,Pi-Ma 1,etc.,only 21 out of 50 stripe rust collections could be differentiated into10 distinctly different races (Y 1 to Y10).However,there were great differencesin pathogenicity among different races so far identified.All the 6 improvedvarieties were resistant to race Y 1 and susceptible to race Y 2.The virulenceof other races differed from one another also pronouncedly. Races Y2,Y3,Y4,Y5 ,Y6,Y7 ,and Y8 were collected from wheat; Y 9 andY10 from Agropyron spp.; and Y1 was collected mainly from Elymus chinense(including 1 collection from wheat).Races Y 1,Y 3.Y 4,Y 5,Y 7,Y 8,Y 9,Y 10were found in Hopeh; Y 1,Y 2,Y 6,Y 7 in Shansi; and Y 6 in Shantung. All collections could be readily grouped into 16 different forms if the highestreaction type was taken as a basis for identification (this method of groupingwas adopted by Fang et al).Comparing the results with that of Fang et al,itappeared that reactions of certain varieties,such as Early Premium,Li-Yung 1 tocollections from North China were distinctly different from their reactions tocollections from East China.This suggested strongly that races of stripe rustorganism between these two regions might be quite different. All wheat varieties tested were found to be resistant to stripe rust collectionsfrom Elymus chinense.whereas collections from Elymus sibiricus and Agropyronspp.were capable of attacking many wheat varieties. Single spore infection of stripe rust frequently resulted in sporulation on thewhole leaf blade.This is definitely much more systemic than infections of eitherstem rust or leaf rust organism.Inoculations with single uredospores and mono-uredospore lines often produced mixtures of infection types ranging from resistantto susceptible on same leaf blades.This is analogous to "X" type reactions re-ported in stem rust and leaf rust literature; therefore,"X" type reaction shouldalso be recognized in the study of stripe rust.

A second-approximation solution for the pressure distribution between two elastic bodies in contact is presented. In addition to the terms used by Hertz as the description of a general surface of contact, the present theory will contain the next higher-order terms of its Taylor's series expansion, such that the coefficients of the Hertz second power terms as well as the dominant fourth-power term is satisfied. Hence, the second order effect is a correction to Hertz theory which increases both with the increase...

A second-approximation solution for the pressure distribution between two elastic bodies in contact is presented. In addition to the terms used by Hertz as the description of a general surface of contact, the present theory will contain the next higher-order terms of its Taylor's series expansion, such that the coefficients of the Hertz second power terms as well as the dominant fourth-power term is satisfied. Hence, the second order effect is a correction to Hertz theory which increases both with the increase of normal load and with the increase of eccentricity of the contact. ellipse. method of change of variables is adopted in the process of integration. The solution, thus obtained, agrees exactly with that obtained by Cattaneo when reduced to his special case of two solids of revolution in contact.To illustrate the usefulness of the present theory, the problem of contact between a ball and the outer race of a ball bearing is studied. Curves are plotted to show that the relative magnitude of the second order effect varies with the shape ratio of the contact ellipse at various normal loads.

Considerable difficulties caused by unstable reactions of wheat varieties were encountered by the authors in the study of physiologic specialization of Puccinia glumarum. The fluctuation of varietal reactions was chiefly due to the variation of light and temperature in ordinary green house. It was found that strict control of temperature (constantly at 15℃) and a stable light source were necessary. Fluorescent lamps serves as a good source of cool light, and a daily supply of 16-hours illumination with an intensity...

Considerable difficulties caused by unstable reactions of wheat varieties were encountered by the authors in the study of physiologic specialization of Puccinia glumarum. The fluctuation of varietal reactions was chiefly due to the variation of light and temperature in ordinary green house. It was found that strict control of temperature (constantly at 15℃) and a stable light source were necessary. Fluorescent lamps serves as a good source of cool light, and a daily supply of 16-hours illumination with an intensity of 4,000 Lux is sufficient for normal development of infection-types. Temperature plays most important role among the environmental factors causing the variability of varietal reactions of wheat to stripe rust. In general, wheat varieties become more resistant to stripe rust as the temperature raises from 10℃ upward. The critical temperature at which host reactions changed from susceptible to resistant varied with different combinations of wheat varieties and races of P. glumarum. Eight variety-race combinations out of 60 had their infection types changed from susceptible to resistant at 15℃, 15 combinations changed at 20℃, 18 combinations at 25℃, while 16 combinations had their resistant infection types unchanged under different temperatures. Highly resistant wheat varieties such as Early Premium, Li-Yung 1, Naking 4179 remained resistant to all 4 races tested under a wide range of light intensities, while highly susceptible variety Ycnta 1885 remained susceptible throughout. Other susceptable varieties behaved rather specifically as light intensity and daily length of illumination varied. Infection type, amount of sporulation and range of cnvironmental conditions for sporulation should all be considered as criteria for the exact evaluation of varietal resistance of wheat and pathogenicity of rust races. Race Y6B isolated from wheat vareity Pima-1, has been proved to be a dangerous race, causing Pima strains severely diseased at 10°—20℃, with the capability to sporulate at 25℃. Race Y6, of which the pathogenicity resembled that of race Y6B on 6 differential hosts, had been(?)olated from Shantung and Shansi provinces during 1954—55. These findings correlated well with the breakdown of Pima 1 in resistance to stripe rust over a wide geographic area since 1955. Early Premium, Naking 4197, Liyung 1 and Nungta 6 are highly resistant varieties to race Y6B.