Harman Patil (Editor)

Wheat yellow rust

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Kingdom
  
Fungi

Class
  
Urediniomycetes

Order
  
Uredinales

Phylum
  
Basidiomycota

Subclass
  
Incertae sedis

Family
  
Pucciniastraceae


Wheat yellow rust (Puccinia striiformis f.sp. tritici), also known as stripe rust, is one of the three wheat rust diseases principally found in wheat grown in cooler environments. Such locations are generally associated with northern latitudes or cooler seasons.

Contents

History

As R.P. Singh, J. Huerta-Espino, and A.P. Roelfs say in their (undated) comprehensive review of literature on the wheat rusts for UN FAO:

"Although Gadd first described stripe rust of wheat in 1777, it was not until 1896 that Eriksson and Henning (1896) showed that stripe rust resulted from a separate pathogen, which they named P. glumarum. In 1953, Hylander et al. (1953) revived the name P. striiformis."

Symptoms

"Yellow rust" takes its name from the appearance of yellow-colored stripes produced parallel along the venations of each leaf blade. These yellow stripes are actually characteristic of uredinia that produce yellow colored urediniospores. Primary hosts of yellow rust are Triticum aestivum (bread wheat), Triticum turgidum (durum wheat), triticale, and a few Hordeum vulgare (barley) cultivars. The alternate host was discovered by accident in 2010. Species of common barberry plants (the alternate host of wheat stem rust) were found harbouring stripe rust. When transferred to grass hosts, Kentucky Bluegrass was successfully infected and urediniospores were produced. Several species of Berberis were then investigated as alternate hosts of Wheat stripe rust and inoculations were successful.

The disease usually occurs early in the growth season, when temperature ranges between 2 and 15 °C; but it may occur to a maximum of 23 °C. High humidity and rainfall are favorable conditions for increasing the infection on both leaf blade and leaf sheath, even on spikes when in epidemic form. Symptoms are stunted and weakened plants, shriveled grains, fewer spikes, loss in number of grains per spike and grain weight. Losses can be 50%, but in severe situations 100% is vulnerable. In countries where wheat is grown in winters or at high elevations, yellow rust is a common threat, but not more significant than wheat leaf rust and stem rust, which are continuous threats in all wheat-growing countries.

Worldwide population structure

The evidence of both spatial structuring and invasion has been shown for this disease. Population genetic analyses indicate a strong regional heterogeneity in levels of recombination, with clear signatures of recombination in the Himalayan and near-Himalayan regions and a predominant clonal population structure in other regions. The existence of a high genotypic diversity, recombinant population structure, high sexual reproduction ability and the abundance of alternate host (Berberis spp.) in the Himalayan and neighboring regions suggest the region as plausible PST center of origin or at least the most closer to its centre of origin. However, further exploration may be useful from Central Asia to East Asian regions.

Disease Management

Breeding resistant varieties is the most cost-effective method to control this rust. Fungicides are available but vary in availability depending on their registration restrictions by national or state governments. Development of varieties resistant to the disease is always an important objective in wheat breeding programs for crop improvement. These resistance genes, however, became ineffective due to the acquisition of virulence to that particular resistance gene rendering the variety susceptible.

References

Wheat yellow rust Wikipedia