Stem Rust: The Causes And Description Of Puccinia Graminis

Cereal rusts became a problem when the first cereal crops were grown in the fertile cresent. However it took two Italian scientists, Fontana and Tozzeti to give us the first detailed description of stem rust fungus in 1767. Thirty years later in 1797 it was given the name Puccinia graminis. Puccinia fungal diseases are the most destructive disease of cereal production. They occur all over the world. Stem rust is a fungal disease caused by the pathogen Puccinia graminis and is a significant disease affecting cereal crops such as wheat, worldwide. A healthy crop of wheat one month off harvest can be severely hit by stem rust and just leave a mass of tangled stems and shrivelled grains. Puccinia graminis is an obligate parasite, which means it
As a result of nuclear fusion and meiosis each teliospore produces haploid basidiospores in the spring. These basidiospores infect the alternate host. Once the alternate host is infected the formation of pycnia in the leaves occurs. For pycniospores to be produced the receptive hyphae of the pycnium must be fertilised by pycniospores from a different mating type. This fertilisation process of the pycnia is a very important aspect of the rust fungus life cycle. Aeciospores are produced on the alternate host. But the aeciospores can only infect wheat plants or other grass hosts. The aeciospores germinate on the wheat plant and produce a uredinium. This final stage of the life cycle is known as the repeating stage. This stage is of huge importance as the aeciospores are the only spores that can infect the host on which they were
Once genetic resistance to stem rust is obtained then no other methods of control should be necessary. However not all cases of genetic resistance are effective. ‘It is estimated that up to 80% of all wheat varieties planted in Asia and Africa are susceptible to Ug99’. (plantwise.org, 2012.)
Fungicides application:
‘Foliar fungicide applications targeting stem rust must be applied as soon as the disease is detected’, (Cereal disease guide, Syngenta). When spraying with fungicides the stem and the leaf of the plant must be covered by the fungicide to be effective. Also it is essential that the plant should be monitored closely in case a follow up application is needed. Usually a follow up application is applied three or four weeks after the first application.
Seed dressing:
When setting the seed fungicides can be applied to the seed which is known as seed dressing. ‘A seed dressing or in furrow fungicide application will control rust fungus for four to six weeks’, (Western Australian Agriculture authority 2011). This seed treatment will benefit the crop hugely and the crop should be a lot healthier than untreated