THE MENDELIAN INHERITANCE OF SUSCEPTI- 

 BILITY AND RESISTANCE TO YELLOW RUST 

 {PUCCINI A GLUM ARUM, ERIKSS. ET HENN.) IN 



WHEAT. 



By S. F. ARMSTRONG, B.A., F.L.S. 

 (Cambridge University Plant Breeding Institute.) 



Contents. 



Section I. INTRODUCTION 



(a) Historical 



(6) Itust scale adopted 



((■) The soil 



(rf) Weather records . 



(e) The parent wheats 



Section II. THE EXPERIMENTAL RESULTS, 1917-1920 



1. The Fj plants, 1917 



2. The F^ generation, 1918 



(A) Climatic conditions in 1918 ....... 



(B) Spread of rust during 1918 



(C) Results obtained: in the F, generation ...... 



3. The F^ cultures, 1919 



(A) Climatic conditions, manuring, and growth of the cultures in 1919 . 



(B) Spread of rust during 1919 ....... 



(C) Results obtained from the F^ cultures ...... 



4. Summary of the F^ results 



5. Application of the F^ results to the F^ statistics . 



6. Results obtained from F2, F^, F^ cultures, etc., in 1920 . 



Section III. SOME OP THE FACTORS WHICH MAY INCREASE OR 

 DIMINISH SUSCEPTIBILITY TO RUST ATTACK 

 Introduction 



(a) Effect of climatic conditions 



(b) Food supply 



(f ) New combinations of parental characters .... 



(d) Variation of susceptibility in hybrid wheats 



(e) Possible effect of environment upon the fungus . 



CONCLUSIONS 



APPENDIX 



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