Bridal creeper rust | |
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Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Basidiomycota |
Class: | Pucciniomycetes |
Order: | Pucciniales |
Family: | Pucciniaceae |
Genus: | Puccinia |
Species: | P. myrsiphylli |
Binomial name | |
Puccinia myrsiphylli | |
Synonyms [1] | |
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Puccinia myrsiphylli is a rust fungus in the genus Puccinia , family Pucciniaceae, and is native to South Africa. [2] It has been tested, introduced, and targeted in Australia and New Zealand as an effective biocontrol agent for Asparagus asparagoides , also known as bridal creeper.
Puccinia myrsiphylli was initially described by Felix von Thümen in 1877. Ethel M. Doidge noted Paul Sydow's 1884 monograph as a resource for this species. [3] P. myrsiphylli was described further in 1926. [4] Later, in 1932, Doidge made an entry describing each section starting with: “[Aecidia],” “Uredo-sori hypophyllous,” and “Teleuto-sori”. She ends this entry by writing, “I have not seen the aecidia.” [3] P. myrsiphylli is in the family Pucciniaceae, and the host-substratum are leaves that are alive from Myrsiphyllum falciforme. [5]
Puccinia myrsiphylli is a rust fungus with the following characteristics: “Uredospores ellipsoid or sub-globose, pale yellow 30-40 x 26-30 μ; epispore hyaline, about 1.5 μ thick, closely and finely echinulate and with 4-5 scattered germ pores…Teleutospores oblong, cuneate or clavate, apex rounded, acuminate or truncate, usually attenuate at the base, usually gently constricted at the septum, light brown, darker at the apex, 43-70 x 17-28 μ; epispore smooth, about 1.5 μ thick, thickened at the apex (up to 7 μ); germ pores obscure, pedicel short, fragile, hyaline or tinged with brown." [3]
The rust fungus shows up in early to late autumn with little, orange structures on the top of the leaves of the A. Asparagoides, and looking like warts. [6] This is the spermagonia and pycnia stage of the disease cycle. [6] Next, there are aecia, which take the form of cup-shapes and are also orange, but they are on the under side of the leaves. [6] The aecia produce aeciospores, and lead to uredinia. [6] Uredinia and telia are on the under side of the leaves, but also on stems. [6] The uredeina are also orange and in the shape of pustules, while the telia are a brown-black color, but also in the shape of pustules. [6] The uredinia produce urediniospores, which are dispersed by the wind. [6] Telia occur several weeks later. [6] Then the telia produce thick-walled resting spores called teliospores. [6]
P. myrsiphylli is likely macrocyclic because it includes all five spores stages. [6] It is also likely autoecious because field reports show that pycnia, aecia, uredinia, and telia of P. myrsiphylli were found on A. asparagoides. [7] No other host plants outside of A. asparagoides are required for P. myrsiphylli to complete its life cycle. [7] The researchers in this study found dormant teliospores on extremely diseased cladodes and stems around spring/early summer time in the winter/rainfall region. [7] This suggests that the fungus survives the dry summer months on debris, when above-ground biomass of host plants have stopped growing. [7] It is the thick-walled teliospores that make sure the rust can survive when bridal creeper deteriorates during the summer. [6] P. myrsipjylli recycles each 3–4 weeks during the summer. [6]
P. myrsiphylli has two natural enemies: Cecidomyiidae larva and Eudarluca caricis. [7] However, these two enemies do not look like they have a major impact on P. myrsiphylli. [7]
Puccinia myrsiphylli is found in Eastern Cape Province in South Africa. [5] P. myrsiphylli was present in South Africa in winter regions, aseasonal regions, and summer rainfall regions in all regions where there is widespread A. asparagoides. [7] In southern Africa, the occurrence of P. myrsiphylli was dependent on the existence of living foliage of its host plant and season of rainfall. [7] P. myrsiphylli is a very flexible pathogen, as shown by its ability to distribute widely throughout many different South African climate regions. [7] It can also survive harsh, dry conditions without its host. [7] P. myrsiphylli can be found in South Africa, Australia, and New Zealand. [7] [8]
Surveys identified Puccinia myrsiphylli as a possible biological control agent for A. asparagoides, which is also called bridal creeper. [9] Bridal creeper is originally from southern Africa, and has been in Australia since 1871. [10] Surveys were conducted in South Africa to find out if P. myrsiphylli would be able to spread as a possible biological control for A. asparagoides. [7] Specificity information was also gathered because safety is a key criterion for introduction of a biological control agent into a different country. [7] A study showed that it had a limited host range, which supported the introduction of the rust into Australia. [7] In 2000, P. myrsiphylli was approved for introduction into Australia (Kleinjan et al., 2004). [7] Conservationists see bridal creeper in areas of native vegetation as a threat, and had approved it as a target of biological control. [10]
In New South Wales, Australia, P. myrsiphylli has been monitored, and there is reason for optimism that it is affecting the growth of A. asparagoides. [7] From July 2000 to November 2001, the rust was monitored at three places in New South Wales: Scheyville National Park near Windsor, Eurobodalla National Park near Moruya, and Bar Beach near Narooma. [4] The monitoring showed that the epidemic could have a heavy and detrimental impact on A. asparagoides. [4] However, the spread was up to 30 m in the first four months after the release, which is relatively slow. [4] A glasshouse experiment was also done. [4] The result was that in the infected plant, the number of tubers, rhizome length, and shoot mass decreased by 60%. [4] P. myrsiphylli builds up resistance and oversummering inoculum which allows it to survive the harsh, dry summer and to return for the next growing season. [4]
The rust fungus Puccinia myrsiphylli requires 8 hours or more of the leaf being wet in order to infect bridal creeper. [4] Between 16 and 20 degrees Celsius is the optimal infection temperature. [4] However, infection is totally stopped at 25 degrees Celsius. [4] In tests, P. myrsiphylli only develops successfully on A. asparagoides. [4] Every other species tested were unaffected or very resistant to the rust. [4] For P. myrsiphylli to be effective, it needs to attack the bridal creeper's root system because 90% of bridal creeper's biomass is below-ground rhizomes and tubers. [4] The way P. myrsiphylli works is by infecting leaves and stems, which cause heavy defoliation of bridal creeper plants. [4] It limits the nutrients and water available for the host plant's production of vegetation and reproduction. [4] P. myrsiphylli also reduces the photosynthetic surface, which destroys leaf tissue. [4] The rust destroys the capacities of A. asparagoides in 20 weeks. [4] Morin believes it will likely take several years for P. myrsiphylli to decrease the biomass below ground. [4]
P. myrsiphylli has gone above and beyond expectations, because it did not die and recolonized at specific places in between seasons. [6] The rust is particularly effective in coastal areas, where conditions are ripe for epidemic growth. [6] Those who use, develop, and manage land in Australia have excitedly used P. myrsiphylli at more than 2,500 locations around Australia. [6] Combining P. myrsiphylli with another biological control agent, a leafhopper, Zygina sp., acted together to lessen the growth of rhizome length and number and biomass of tubers in A. asparagoides. [11] In addition, a long-term 7-year study has shown decreases in seedling, shoot numbers, and above-ground biomass of A. asparagoides across all sites that were observed (using the biological control agents of the leafhopper and P. myrsiphylli). [12] Some sites recorded greater declines in A. asparagoides on trellises than others due to varying climate and leafhopper factors. [12] Due to the expansive nature of the study, scientists feel confident that the biocontrol agents of leafhopper and Puccinia myrsiphylli played a role in the decline of A. asparagoides. [12]
After P. myrsiphylli was introduced in Australia, it was also detected in New Zealand. [9] New Zealand is also trying to find ways to deal with undesirable weeds. [13] Invasive exotic weeds have a negative impact on production and biodiversity. [13] Puccinia myrsiphylli has spread across bridal creeper's range in northern New Zealand. [8] It as an effective biocontrol agent in New Zealand. [8] P. myrsiphylli is seen as a high quality example of effective biological control in New Zealand's 90-year history of weed biocontrol studies. [13] P. myrsiphylli is likely effective by itself, but it has also been tested with other fungal pathogens. [8] For example, it has been tested with Colletotrichum Gloeosporioides. [8] In that test C. Gloeosporioides was only mildly effective on its own. [8] This illustrates that P. myrsiphylli is seen as the most impactful biological control agent in this situation. [6] The Environmental Risk Management Authority of New Zealand was attempting to “de-new” the classification of Puccinia myrsiphylli, which would allow those who use, develop, and manage land in Australia to manipulate P. myrsiphylli for even greater biocontrol effectiveness. [8]
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