|
Puccinia coronata f. sp. avenae
Puccinia coronata f. sp. avenae is the variation (forma specialis, f. sp.) of the crown rust fungus (Puccinia coronata) which infects oat plants (Avena sativa).[1] Almost every growing region of oat has been affected by this pathogen at one point or another.[2] During particularly bad epidemics, the worldwide crop yields have been reduced by up to 40%.[2] One reason why Pca has such a prominent effect is that the conditions which favor oat production also favor the growth and inoculation of the rusts: Meaning that years in which the highest yields of crops are expected are the same years in which losses are the highest as well.[2] Pca urediniospores germinate the best at temperature between 10–30 °C (50–86 °F) with germ-tube growth optimized at 20 °C (68 °F).[3] The virulence of Pca and the resistance of wild oat plants is a highly studied topic. It seems that the resistance level of the oat plant is dependent upon which race of Pca is acting on it; the virulence of the fungal pathogen also seems to depend upon which strain the strain of oat being attacked.[4] There are most likely multiple traits that control both virulence and resistance which suggests a very interactive host-parasite coevolution.[4] A few specific loci have been found to confer resistance such as Pca which conferred a dominant, resistant phenotype to nine different isolates of P. coronata.[5] An additional isolate of P. coronata was also resisted, although another, un-linked gene may be involved which correlates the theory that resistance and virulence in A. sativa are controlled by multiple genes.[5] Some studies suggest that the responses are dependent upon the physiological race of the rust involved due to mutations that arise in separate races.[6] One way in which the expression of certain genes has been found to combat Pca is through the production of avenalumins.[1] Avenalumins are antimicrobial compounds which inhibit hyphal growth, thus preventing P. coronata from spreading.[1] Avenalumins are only found in infected areas of plants and nowhere else.[1] The production of avenalumins is regulated by some of the same genes that have been found to confer resistance in certain lines of oats, thus indicating their importance in resistance.[1] In addition to total resistance to specific races, in such cases as the production avenalumins, partial or horizontal resistance provides a way to reduce the effect of P. coronata.[7] References
|
||||||||||||||||||||||||||||
Portal di Ensiklopedia Dunia
