Plant Sciences


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Disease Resistance


Historic Plot 30Much of the soil in the North Central flax growing area is infested with the wilt organism.  An established testing program of seeding in infested soils is available for evaluation of wilt tolerance.  ‘Plot 30' was established as part of a rotation study in the 1880s.  The continuous flax plot has been grown to flax every year since 1884.  Bolley was successful in using the ‘Plot’ to select wilt tolerant flax cultivars.  All cultivars grown in the flax growing region of North America have used the ‘Plot 30' in the development phase or final testing prior to release for production.



Flax rustPhysiological specialization of Melampsora lini was first demonstrated by Flor.  Studies on the inheritance of reaction to flax rust and on the genetics of pathogenicity in the rust organism have indicated that for each gene conditioning resistance to rust in the host there was a specific gene for pathogenicity in the pathogen.  Utilizing existing germplasm, evaluation of cultivars of flax resistant or immune to North American races of rust should involve only routine greenhouse testing.  In 1973, the change of races of flax rust attacking flax generated interest in the development of cultivars with more than one source of resistance to known local races.  A system was proposed  to utilize races of rust in the development of two-gene cultivars.  At that time, only selected genetic backgrounds with selected gene combinations could be evaluated without extensive backcrossing. Cultivar development with two effective genes conditioning resistance to all known North American races of rust have resulted in the release of several cultivars including 'Flor' and 'Linton'.  The development of cultivars with at least two genes for resistance is more time consuming and requires greater cooperation with plant pathologists than breeding for single gene resistance.  Statler developed races of flax rust to assist the breeding of multiple gene lines.  With rust races now available for testing, two-gene sources of resistance can be incorporated into a wider background of material.



PasmoPasmo (Septoria linicola Speg. Garass), a disease generally considered to be of minor importance, has caused considerable damage to flax in certain areas in the flax growing area.  Although no cultivar of flax is classified as resistant to the pasmo organism, cultivars vary in degree of susceptibility.





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